[PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[Zixing Liu]

This ioctl can be used by userspace applications to determine which
(special) registers are get/set-able.

This can be very useful for cross-platform VMMs so that they do not have
to hardcode register indices for each supported architectures.

Signed-off-by: Zixing Liu <liushuyu@aosc.io>
---

For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
VirtualBox-kvm in the future.

 Documentation/virt/kvm/api.rst |  2 +-
 arch/loongarch/kvm/vcpu.c      | 69 ++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 01a3abef8abb..f46dd8be282f 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -3603,7 +3603,7 @@ VCPU matching underlying host.
 ---------------------
 
 :Capability: basic
-:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
+:Architectures: arm64, loongarch, mips, riscv, x86 (if KVM_CAP_ONE_REG)
 :Type: vcpu ioctl
 :Parameters: struct kvm_reg_list (in/out)
 :Returns: 0 on success; -1 on error
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index 656b954c1134..b884eb9c76aa 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
 	return ret;
 }
 
+static unsigned long kvm_loongarch_num_lbt_regs(void)
+{
+	/* +1 for the LBT_FTOP flag (inside arch.fpu) */
+	return sizeof(struct loongarch_lbt) / sizeof(unsigned long) + 1;
+}
+
+static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
+{
+	/* +1 for the KVM_REG_LOONGARCH_COUNTER register */
+	unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
+
+	if (kvm_guest_has_lbt(&vcpu->arch))
+		res += kvm_loongarch_num_lbt_regs();
+
+	return res;
+}
+
+static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
+					  u64 __user *uindices)
+{
+	u64 reg;
+	unsigned int i;
+
+	for (i = 0; i < CSR_MAX_NUMS; i++) {
+		reg = KVM_IOC_CSRID(i);
+		if (put_user(reg, uindices++))
+			return -EFAULT;
+	}
+
+	for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
+		reg = KVM_IOC_CPUCFG(i);
+		if (put_user(reg, uindices++))
+			return -EFAULT;
+	}
+
+	reg = KVM_REG_LOONGARCH_COUNTER;
+	if (put_user(reg, uindices++))
+		return -EFAULT;
+
+	if (!kvm_guest_has_lbt(&vcpu->arch))
+		return 0;
+
+	for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
+		reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
+		if (put_user(reg, uindices++))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
 long kvm_arch_vcpu_ioctl(struct file *filp,
 			 unsigned int ioctl, unsigned long arg)
 {
@@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
 		break;
 	}
+	case KVM_GET_REG_LIST: {
+		struct kvm_reg_list __user *user_list = argp;
+		struct kvm_reg_list reg_list;
+		unsigned n;
+
+		r = -EFAULT;
+		if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
+			break;
+		n = reg_list.n;
+		reg_list.n = kvm_loongarch_num_regs(vcpu);
+		if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
+			break;
+		r = -E2BIG;
+		if (n < reg_list.n)
+			break;
+		r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
+		break;
+	}
 	default:
 		r = -ENOIOCTLCMD;
 		break;
-- 
2.52.0

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[Bibo Mao]

On 2026/1/25 下午1:43, Zixing Liu wrote:
> This ioctl can be used by userspace applications to determine which
> (special) registers are get/set-able.
> 
> This can be very useful for cross-platform VMMs so that they do not have
> to hardcode register indices for each supported architectures.
> 
> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
> ---
> 
> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
> VirtualBox-kvm in the future.
> 
>   Documentation/virt/kvm/api.rst |  2 +-
>   arch/loongarch/kvm/vcpu.c      | 69 ++++++++++++++++++++++++++++++++++
>   2 files changed, 70 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 01a3abef8abb..f46dd8be282f 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>   ---------------------
>   
>   :Capability: basic
> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
> +:Architectures: arm64, loongarch, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>   :Type: vcpu ioctl
>   :Parameters: struct kvm_reg_list (in/out)
>   :Returns: 0 on success; -1 on error
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index 656b954c1134..b884eb9c76aa 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
>   	return ret;
>   }
>   
> +static unsigned long kvm_loongarch_num_lbt_regs(void)
> +{
> +	/* +1 for the LBT_FTOP flag (inside arch.fpu) */
> +	return sizeof(struct loongarch_lbt) / sizeof(unsigned long) + 1;
> +}
> +
> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
> +{
> +	/* +1 for the KVM_REG_LOONGARCH_COUNTER register */
> +	unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
> +
> +	if (kvm_guest_has_lbt(&vcpu->arch))
> +		res += kvm_loongarch_num_lbt_regs();
> +
> +	return res;
> +}
> +
> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
> +					  u64 __user *uindices)
> +{
> +	u64 reg;
> +	unsigned int i;
> +
> +	for (i = 0; i < CSR_MAX_NUMS; i++) {
> +		reg = KVM_IOC_CSRID(i);
> +		if (put_user(reg, uindices++))
> +			return -EFAULT;
> +	}
CSR_MAX_NUMS is max number of accessible CSR registers, instead only 
part of them is used by vCPU model. By my understanding, there will be 
no much meaning if CSR_MAX_NUMS is returned. And I think it will be 
better if real CSR register id and number is returned.

Regards
Bibo Mao
> +
> +	for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
> +		reg = KVM_IOC_CPUCFG(i);
> +		if (put_user(reg, uindices++))
> +			return -EFAULT;
> +	}
> +
> +	reg = KVM_REG_LOONGARCH_COUNTER;
> +	if (put_user(reg, uindices++))
> +		return -EFAULT;
> +
> +	if (!kvm_guest_has_lbt(&vcpu->arch))
> +		return 0;
> +
> +	for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
> +		reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
> +		if (put_user(reg, uindices++))
> +			return -EFAULT;
> +	}
> +
> +	return 0;
> +}
> +
>   long kvm_arch_vcpu_ioctl(struct file *filp,
>   			 unsigned int ioctl, unsigned long arg)
>   {
> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>   		r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>   		break;
>   	}
> +	case KVM_GET_REG_LIST: {
> +		struct kvm_reg_list __user *user_list = argp;
> +		struct kvm_reg_list reg_list;
> +		unsigned n;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
> +			break;
> +		n = reg_list.n;
> +		reg_list.n = kvm_loongarch_num_regs(vcpu);
> +		if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
> +			break;
> +		r = -E2BIG;
> +		if (n < reg_list.n)
> +			break;
> +		r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
> +		break;
> +	}
>   	default:
>   		r = -ENOIOCTLCMD;
>   		break;
> 

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[liushuyu]

Hi Bibo,
>
>
> On 2026/1/25 下午1:43, Zixing Liu wrote:
>> This ioctl can be used by userspace applications to determine which
>> (special) registers are get/set-able.
>>
>> This can be very useful for cross-platform VMMs so that they do not have
>> to hardcode register indices for each supported architectures.
>>
>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>> ---
>>
>> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
>> VirtualBox-kvm in the future.
>>
>>   Documentation/virt/kvm/api.rst |  2 +-
>>   arch/loongarch/kvm/vcpu.c      | 69 ++++++++++++++++++++++++++++++++++
>>   2 files changed, 70 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/virt/kvm/api.rst
>> b/Documentation/virt/kvm/api.rst
>> index 01a3abef8abb..f46dd8be282f 100644
>> --- a/Documentation/virt/kvm/api.rst
>> +++ b/Documentation/virt/kvm/api.rst
>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>   ---------------------
>>     :Capability: basic
>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>   :Type: vcpu ioctl
>>   :Parameters: struct kvm_reg_list (in/out)
>>   :Returns: 0 on success; -1 on error
>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>> index 656b954c1134..b884eb9c76aa 100644
>> --- a/arch/loongarch/kvm/vcpu.c
>> +++ b/arch/loongarch/kvm/vcpu.c
>> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct
>> kvm_vcpu *vcpu,
>>       return ret;
>>   }
>>   +static unsigned long kvm_loongarch_num_lbt_regs(void)
>> +{
>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long) + 1;
>> +}
>> +
>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>> +{
>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>> +
>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>> +        res += kvm_loongarch_num_lbt_regs();
>> +
>> +    return res;
>> +}
>> +
>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>> +                      u64 __user *uindices)
>> +{
>> +    u64 reg;
>> +    unsigned int i;
>> +
>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>> +        reg = KVM_IOC_CSRID(i);
>> +        if (put_user(reg, uindices++))
>> +            return -EFAULT;
>> +    }
> CSR_MAX_NUMS is max number of accessible CSR registers, instead only
> part of them is used by vCPU model. By my understanding, there will be
> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
> better if real CSR register id and number is returned. 
>
Did you mean we should only return the CSR registers initialized in this
function
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
?

That looks like a very large list and the values of the register IDs are
not fully continuous. If that is the case, how do we maintain the
get/set-able CSR register list?

> Regards
> Bibo Mao
>> +
>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>> +        reg = KVM_IOC_CPUCFG(i);
>> +        if (put_user(reg, uindices++))
>> +            return -EFAULT;
>> +    }
>> +
>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>> +    if (put_user(reg, uindices++))
>> +        return -EFAULT;
>> +
>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>> +        return 0;
>> +
>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>> +        if (put_user(reg, uindices++))
>> +            return -EFAULT;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   long kvm_arch_vcpu_ioctl(struct file *filp,
>>                unsigned int ioctl, unsigned long arg)
>>   {
>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>           r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>           break;
>>       }
>> +    case KVM_GET_REG_LIST: {
>> +        struct kvm_reg_list __user *user_list = argp;
>> +        struct kvm_reg_list reg_list;
>> +        unsigned n;
>> +
>> +        r = -EFAULT;
>> +        if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
>> +            break;
>> +        n = reg_list.n;
>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>> +            break;
>> +        r = -E2BIG;
>> +        if (n < reg_list.n)
>> +            break;
>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>> +        break;
>> +    }
>>       default:
>>           r = -ENOIOCTLCMD;
>>           break;
>>
>
Thanks,
Zixing

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[Bibo Mao]

On 2026/1/26 上午11:38, liushuyu wrote:
> Hi Bibo,
>>
>>
>> On 2026/1/25 下午1:43, Zixing Liu wrote:
>>> This ioctl can be used by userspace applications to determine which
>>> (special) registers are get/set-able.
>>>
>>> This can be very useful for cross-platform VMMs so that they do not have
>>> to hardcode register indices for each supported architectures.
>>>
>>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>>> ---
>>>
>>> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
>>> VirtualBox-kvm in the future.
>>>
>>>    Documentation/virt/kvm/api.rst |  2 +-
>>>    arch/loongarch/kvm/vcpu.c      | 69 ++++++++++++++++++++++++++++++++++
>>>    2 files changed, 70 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/virt/kvm/api.rst
>>> b/Documentation/virt/kvm/api.rst
>>> index 01a3abef8abb..f46dd8be282f 100644
>>> --- a/Documentation/virt/kvm/api.rst
>>> +++ b/Documentation/virt/kvm/api.rst
>>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>>    ---------------------
>>>      :Capability: basic
>>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>>    :Type: vcpu ioctl
>>>    :Parameters: struct kvm_reg_list (in/out)
>>>    :Returns: 0 on success; -1 on error
>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>> index 656b954c1134..b884eb9c76aa 100644
>>> --- a/arch/loongarch/kvm/vcpu.c
>>> +++ b/arch/loongarch/kvm/vcpu.c
>>> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct
>>> kvm_vcpu *vcpu,
>>>        return ret;
>>>    }
>>>    +static unsigned long kvm_loongarch_num_lbt_regs(void)
>>> +{
>>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long) + 1;
>>> +}
>>> +
>>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>>> +{
>>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>>> +
>>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>>> +        res += kvm_loongarch_num_lbt_regs();
>>> +
>>> +    return res;
>>> +}
>>> +
>>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>> +                      u64 __user *uindices)
>>> +{
>>> +    u64 reg;
>>> +    unsigned int i;
>>> +
>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>> +        reg = KVM_IOC_CSRID(i);
>>> +        if (put_user(reg, uindices++))
>>> +            return -EFAULT;
>>> +    }
>> CSR_MAX_NUMS is max number of accessible CSR registers, instead only
>> part of them is used by vCPU model. By my understanding, there will be
>> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
>> better if real CSR register id and number is returned.
>>
> Did you mean we should only return the CSR registers initialized in this
> function
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
> ?
> 
> That looks like a very large list and the values of the register IDs are
> not fully continuous. If that is the case, how do we maintain the
> get/set-able CSR register list?
It will be better if CSR register list can be categorized, for example 
with LoongArch CPU manual CSR register is split into 8 types from 
chapter 7.4 -- 7.11

At the beginning, there is big array with size CSR_MAX_NUMS without any 
category, it can be fine-gained in late.

Regards
Bibo Mao
> 
>> Regards
>> Bibo Mao
>>> +
>>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>>> +        reg = KVM_IOC_CPUCFG(i);
>>> +        if (put_user(reg, uindices++))
>>> +            return -EFAULT;
>>> +    }
>>> +
>>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>>> +    if (put_user(reg, uindices++))
>>> +        return -EFAULT;
>>> +
>>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>>> +        return 0;
>>> +
>>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>>> +        if (put_user(reg, uindices++))
>>> +            return -EFAULT;
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +
>>>    long kvm_arch_vcpu_ioctl(struct file *filp,
>>>                 unsigned int ioctl, unsigned long arg)
>>>    {
>>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>>            r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>>            break;
>>>        }
>>> +    case KVM_GET_REG_LIST: {
>>> +        struct kvm_reg_list __user *user_list = argp;
>>> +        struct kvm_reg_list reg_list;
>>> +        unsigned n;
>>> +
>>> +        r = -EFAULT;
>>> +        if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
>>> +            break;
>>> +        n = reg_list.n;
>>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>>> +            break;
>>> +        r = -E2BIG;
>>> +        if (n < reg_list.n)
>>> +            break;
>>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>>> +        break;
>>> +    }
>>>        default:
>>>            r = -ENOIOCTLCMD;
>>>            break;
>>>
>>
> Thanks,
> Zixing
> 

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[liushuyu]

Hi Bibo,

>
>
> On 2026/1/26 上午11:38, liushuyu wrote:
>> Hi Bibo,
>>>
>>>
>>> On 2026/1/25 下午1:43, Zixing Liu wrote:
>>>> This ioctl can be used by userspace applications to determine which
>>>> (special) registers are get/set-able.
>>>>
>>>> This can be very useful for cross-platform VMMs so that they do not
>>>> have
>>>> to hardcode register indices for each supported architectures.
>>>>
>>>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>>>> ---
>>>>
>>>> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
>>>> VirtualBox-kvm in the future.
>>>>
>>>>    Documentation/virt/kvm/api.rst |  2 +-
>>>>    arch/loongarch/kvm/vcpu.c      | 69
>>>> ++++++++++++++++++++++++++++++++++
>>>>    2 files changed, 70 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/Documentation/virt/kvm/api.rst
>>>> b/Documentation/virt/kvm/api.rst
>>>> index 01a3abef8abb..f46dd8be282f 100644
>>>> --- a/Documentation/virt/kvm/api.rst
>>>> +++ b/Documentation/virt/kvm/api.rst
>>>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>>>    ---------------------
>>>>      :Capability: basic
>>>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if
>>>> KVM_CAP_ONE_REG)
>>>>    :Type: vcpu ioctl
>>>>    :Parameters: struct kvm_reg_list (in/out)
>>>>    :Returns: 0 on success; -1 on error
>>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>>> index 656b954c1134..b884eb9c76aa 100644
>>>> --- a/arch/loongarch/kvm/vcpu.c
>>>> +++ b/arch/loongarch/kvm/vcpu.c
>>>> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct
>>>> kvm_vcpu *vcpu,
>>>>        return ret;
>>>>    }
>>>>    +static unsigned long kvm_loongarch_num_lbt_regs(void)
>>>> +{
>>>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>>>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long) + 1;
>>>> +}
>>>> +
>>>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>>>> +{
>>>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>>>> +
>>>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>>>> +        res += kvm_loongarch_num_lbt_regs();
>>>> +
>>>> +    return res;
>>>> +}
>>>> +
>>>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>>> +                      u64 __user *uindices)
>>>> +{
>>>> +    u64 reg;
>>>> +    unsigned int i;
>>>> +
>>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>>> +        reg = KVM_IOC_CSRID(i);
>>>> +        if (put_user(reg, uindices++))
>>>> +            return -EFAULT;
>>>> +    }
>>> CSR_MAX_NUMS is max number of accessible CSR registers, instead only
>>> part of them is used by vCPU model. By my understanding, there will be
>>> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
>>> better if real CSR register id and number is returned.
>>>
>> Did you mean we should only return the CSR registers initialized in this
>> function
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
>>
>> ?
>>
>> That looks like a very large list and the values of the register IDs are
>> not fully continuous. If that is the case, how do we maintain the
>> get/set-able CSR register list?
> It will be better if CSR register list can be categorized, for example
> with LoongArch CPU manual CSR register is split into 8 types from
> chapter 7.4 -- 7.11
>
> At the beginning, there is big array with size CSR_MAX_NUMS without
> any category, it can be fine-gained in late. 

Does that mean in the new `kvm_loongarch_copy_reg_indices` function, it
is also okay to embed this big list in there?

Or do you want to extract the list from the `kvm_init_gcsr_flag`
function and refactor both functions to share one single big list
(probably in the kvm_host.h header)?

Because from what I could understand, your previous messages point to
that we need to use this list to make out what CSR registers to return
to the user space VMMs.

>
> Regards
> Bibo Mao
>>
>>> Regards
>>> Bibo Mao
>>>> +
>>>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>>>> +        reg = KVM_IOC_CPUCFG(i);
>>>> +        if (put_user(reg, uindices++))
>>>> +            return -EFAULT;
>>>> +    }
>>>> +
>>>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>>>> +    if (put_user(reg, uindices++))
>>>> +        return -EFAULT;
>>>> +
>>>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>>>> +        return 0;
>>>> +
>>>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>>>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>>>> +        if (put_user(reg, uindices++))
>>>> +            return -EFAULT;
>>>> +    }
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>>    long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>                 unsigned int ioctl, unsigned long arg)
>>>>    {
>>>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>            r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>>>            break;
>>>>        }
>>>> +    case KVM_GET_REG_LIST: {
>>>> +        struct kvm_reg_list __user *user_list = argp;
>>>> +        struct kvm_reg_list reg_list;
>>>> +        unsigned n;
>>>> +
>>>> +        r = -EFAULT;
>>>> +        if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
>>>> +            break;
>>>> +        n = reg_list.n;
>>>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>>>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>>>> +            break;
>>>> +        r = -E2BIG;
>>>> +        if (n < reg_list.n)
>>>> +            break;
>>>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>>>> +        break;
>>>> +    }
>>>>        default:
>>>>            r = -ENOIOCTLCMD;
>>>>            break;
>>>>
>>>
>> Thanks,
>> Zixing
>>
>
Thanks,
Zixing

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[Bibo Mao]

On 2026/1/26 下午12:22, liushuyu wrote:
> Hi Bibo,
> 
>>
>>
>> On 2026/1/26 上午11:38, liushuyu wrote:
>>> Hi Bibo,
>>>>
>>>>
>>>> On 2026/1/25 下午1:43, Zixing Liu wrote:
>>>>> This ioctl can be used by userspace applications to determine which
>>>>> (special) registers are get/set-able.
>>>>>
>>>>> This can be very useful for cross-platform VMMs so that they do not
>>>>> have
>>>>> to hardcode register indices for each supported architectures.
>>>>>
>>>>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>>>>> ---
>>>>>
>>>>> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
>>>>> VirtualBox-kvm in the future.
>>>>>
>>>>>     Documentation/virt/kvm/api.rst |  2 +-
>>>>>     arch/loongarch/kvm/vcpu.c      | 69
>>>>> ++++++++++++++++++++++++++++++++++
>>>>>     2 files changed, 70 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/Documentation/virt/kvm/api.rst
>>>>> b/Documentation/virt/kvm/api.rst
>>>>> index 01a3abef8abb..f46dd8be282f 100644
>>>>> --- a/Documentation/virt/kvm/api.rst
>>>>> +++ b/Documentation/virt/kvm/api.rst
>>>>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>>>>     ---------------------
>>>>>       :Capability: basic
>>>>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>>>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if
>>>>> KVM_CAP_ONE_REG)
>>>>>     :Type: vcpu ioctl
>>>>>     :Parameters: struct kvm_reg_list (in/out)
>>>>>     :Returns: 0 on success; -1 on error
>>>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>>>> index 656b954c1134..b884eb9c76aa 100644
>>>>> --- a/arch/loongarch/kvm/vcpu.c
>>>>> +++ b/arch/loongarch/kvm/vcpu.c
>>>>> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct
>>>>> kvm_vcpu *vcpu,
>>>>>         return ret;
>>>>>     }
>>>>>     +static unsigned long kvm_loongarch_num_lbt_regs(void)
>>>>> +{
>>>>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>>>>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long) + 1;
>>>>> +}
>>>>> +
>>>>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>>>>> +{
>>>>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>>>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>>>>> +
>>>>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>>>>> +        res += kvm_loongarch_num_lbt_regs();
>>>>> +
>>>>> +    return res;
>>>>> +}
>>>>> +
>>>>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>>>> +                      u64 __user *uindices)
>>>>> +{
>>>>> +    u64 reg;
>>>>> +    unsigned int i;
>>>>> +
>>>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>>>> +        reg = KVM_IOC_CSRID(i);
>>>>> +        if (put_user(reg, uindices++))
>>>>> +            return -EFAULT;
>>>>> +    }
>>>> CSR_MAX_NUMS is max number of accessible CSR registers, instead only
>>>> part of them is used by vCPU model. By my understanding, there will be
>>>> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
>>>> better if real CSR register id and number is returned.
>>>>
>>> Did you mean we should only return the CSR registers initialized in this
>>> function
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
>>>
>>> ?
>>>
>>> That looks like a very large list and the values of the register IDs are
>>> not fully continuous. If that is the case, how do we maintain the
>>> get/set-able CSR register list?
>> It will be better if CSR register list can be categorized, for example
>> with LoongArch CPU manual CSR register is split into 8 types from
>> chapter 7.4 -- 7.11
>>
>> At the beginning, there is big array with size CSR_MAX_NUMS without
>> any category, it can be fine-gained in late.
> 
> Does that mean in the new `kvm_loongarch_copy_reg_indices` function, it
> is also okay to embed this big list in there?
Firstly I do not know how to use ioctl command KVM_GET_REG_LIST in VMM 
actually.

At the second from the word "determine which (special) registers are 
get/set-able", I think that it is better to set accessible CSR register 
number and ID rather than the total number CSR_MAX_NUMS.

+static int kvm_loongarch_num_csr_regs(struct kvm_vcpu *vcpu)
+{
+	unsigned int i, count;
+
+	count = 0
+	for (i = 0; i < CSR_MAX_NUMS; i++) {
+		if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
+			continue;
+		count++;
+	}
+	return count;
+}

static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
{
	/* +1 for the KVM_REG_LOONGARCH_COUNTER register */
+	unsigned long res = kvm_loongarch_num_csr_regs + KVM_MAX_CPUCFG_REGS + 1;

	if (kvm_guest_has_lbt(&vcpu->arch))
		res += kvm_loongarch_num_lbt_regs();

	return res;
}

static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
					  u64 __user *uindices)
{
	u64 reg;
	unsigned int i;

	for (i = 0; i < CSR_MAX_NUMS; i++) {
+                if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
+                    continue;
		reg = KVM_IOC_CSRID(i);
		if (put_user(reg, uindices++))
			return -EFAULT;
	}

Regards
Bibo Mao
> 
> Or do you want to extract the list from the `kvm_init_gcsr_flag`
> function and refactor both functions to share one single big list
> (probably in the kvm_host.h header)?
> 
> Because from what I could understand, your previous messages point to
> that we need to use this list to make out what CSR registers to return
> to the user space VMMs.

> 
>>
>> Regards
>> Bibo Mao
>>>
>>>> Regards
>>>> Bibo Mao
>>>>> +
>>>>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>>>>> +        reg = KVM_IOC_CPUCFG(i);
>>>>> +        if (put_user(reg, uindices++))
>>>>> +            return -EFAULT;
>>>>> +    }
>>>>> +
>>>>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>>>>> +    if (put_user(reg, uindices++))
>>>>> +        return -EFAULT;
>>>>> +
>>>>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>>>>> +        return 0;
>>>>> +
>>>>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>>>>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>>>>> +        if (put_user(reg, uindices++))
>>>>> +            return -EFAULT;
>>>>> +    }
>>>>> +
>>>>> +    return 0;
>>>>> +}
>>>>> +
>>>>>     long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>                  unsigned int ioctl, unsigned long arg)
>>>>>     {
>>>>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>             r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>>>>             break;
>>>>>         }
>>>>> +    case KVM_GET_REG_LIST: {
>>>>> +        struct kvm_reg_list __user *user_list = argp;
>>>>> +        struct kvm_reg_list reg_list;
>>>>> +        unsigned n;
>>>>> +
>>>>> +        r = -EFAULT;
>>>>> +        if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
>>>>> +            break;
>>>>> +        n = reg_list.n;
>>>>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>>>>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>>>>> +            break;
>>>>> +        r = -E2BIG;
>>>>> +        if (n < reg_list.n)
>>>>> +            break;
>>>>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>>>>> +        break;
>>>>> +    }
>>>>>         default:
>>>>>             r = -ENOIOCTLCMD;
>>>>>             break;
>>>>>
>>>>
>>> Thanks,
>>> Zixing
>>>
>>
> Thanks,
> Zixing
> 

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[liushuyu]

Hi Bibo,

>
>
> On 2026/1/26 下午12:22, liushuyu wrote:
>> Hi Bibo,
>>
>>>
>>>
>>> On 2026/1/26 上午11:38, liushuyu wrote:
>>>> Hi Bibo,
>>>>>
>>>>>
>>>>> On 2026/1/25 下午1:43, Zixing Liu wrote:
>>>>>> This ioctl can be used by userspace applications to determine which
>>>>>> (special) registers are get/set-able.
>>>>>>
>>>>>> This can be very useful for cross-platform VMMs so that they do not
>>>>>> have
>>>>>> to hardcode register indices for each supported architectures.
>>>>>>
>>>>>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>>>>>> ---
>>>>>>
>>>>>> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
>>>>>> VirtualBox-kvm in the future.
>>>>>>
>>>>>>     Documentation/virt/kvm/api.rst |  2 +-
>>>>>>     arch/loongarch/kvm/vcpu.c      | 69
>>>>>> ++++++++++++++++++++++++++++++++++
>>>>>>     2 files changed, 70 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/Documentation/virt/kvm/api.rst
>>>>>> b/Documentation/virt/kvm/api.rst
>>>>>> index 01a3abef8abb..f46dd8be282f 100644
>>>>>> --- a/Documentation/virt/kvm/api.rst
>>>>>> +++ b/Documentation/virt/kvm/api.rst
>>>>>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>>>>>     ---------------------
>>>>>>       :Capability: basic
>>>>>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>>>>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if
>>>>>> KVM_CAP_ONE_REG)
>>>>>>     :Type: vcpu ioctl
>>>>>>     :Parameters: struct kvm_reg_list (in/out)
>>>>>>     :Returns: 0 on success; -1 on error
>>>>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>>>>> index 656b954c1134..b884eb9c76aa 100644
>>>>>> --- a/arch/loongarch/kvm/vcpu.c
>>>>>> +++ b/arch/loongarch/kvm/vcpu.c
>>>>>> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct
>>>>>> kvm_vcpu *vcpu,
>>>>>>         return ret;
>>>>>>     }
>>>>>>     +static unsigned long kvm_loongarch_num_lbt_regs(void)
>>>>>> +{
>>>>>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>>>>>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long)
>>>>>> + 1;
>>>>>> +}
>>>>>> +
>>>>>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>>>>>> +{
>>>>>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>>>>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>>>>>> +
>>>>>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>>>>>> +        res += kvm_loongarch_num_lbt_regs();
>>>>>> +
>>>>>> +    return res;
>>>>>> +}
>>>>>> +
>>>>>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>>>>> +                      u64 __user *uindices)
>>>>>> +{
>>>>>> +    u64 reg;
>>>>>> +    unsigned int i;
>>>>>> +
>>>>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>>>>> +        reg = KVM_IOC_CSRID(i);
>>>>>> +        if (put_user(reg, uindices++))
>>>>>> +            return -EFAULT;
>>>>>> +    }
>>>>> CSR_MAX_NUMS is max number of accessible CSR registers, instead only
>>>>> part of them is used by vCPU model. By my understanding, there
>>>>> will be
>>>>> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
>>>>> better if real CSR register id and number is returned.
>>>>>
>>>> Did you mean we should only return the CSR registers initialized in
>>>> this
>>>> function
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
>>>>
>>>>
>>>> ?
>>>>
>>>> That looks like a very large list and the values of the register
>>>> IDs are
>>>> not fully continuous. If that is the case, how do we maintain the
>>>> get/set-able CSR register list?
>>> It will be better if CSR register list can be categorized, for example
>>> with LoongArch CPU manual CSR register is split into 8 types from
>>> chapter 7.4 -- 7.11
>>>
>>> At the beginning, there is big array with size CSR_MAX_NUMS without
>>> any category, it can be fine-gained in late.
>>
>> Does that mean in the new `kvm_loongarch_copy_reg_indices` function, it
>> is also okay to embed this big list in there?
> Firstly I do not know how to use ioctl command KVM_GET_REG_LIST in VMM
> actually.
>
> At the second from the word "determine which (special) registers are
> get/set-able", I think that it is better to set accessible CSR
> register number and ID rather than the total number CSR_MAX_NUMS. 
>
Understood. I will post a v2 patch, and we can continue the discussion
from there to see if I understood your points correctly.

> +static int kvm_loongarch_num_csr_regs(struct kvm_vcpu *vcpu)
> +{
> +    unsigned int i, count;
> +
> +    count = 0
> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
> +        if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
> +            continue;
> +        count++;
> +    }
> +    return count;
> +}
>
> static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
> {
>     /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
> +    unsigned long res = kvm_loongarch_num_csr_regs +
> KVM_MAX_CPUCFG_REGS + 1;
>
>     if (kvm_guest_has_lbt(&vcpu->arch))
>         res += kvm_loongarch_num_lbt_regs();
>
>     return res;
> }
>
> static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>                       u64 __user *uindices)
> {
>     u64 reg;
>     unsigned int i;
>
>     for (i = 0; i < CSR_MAX_NUMS; i++) {
> +                if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
> +                    continue;
>         reg = KVM_IOC_CSRID(i);
>         if (put_user(reg, uindices++))
>             return -EFAULT;
>     }
>
> Regards
> Bibo Mao
>>
>> Or do you want to extract the list from the `kvm_init_gcsr_flag`
>> function and refactor both functions to share one single big list
>> (probably in the kvm_host.h header)?
>>
>> Because from what I could understand, your previous messages point to
>> that we need to use this list to make out what CSR registers to return
>> to the user space VMMs.
>
>>
>>>
>>> Regards
>>> Bibo Mao
>>>>
>>>>> Regards
>>>>> Bibo Mao
>>>>>> +
>>>>>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>>>>>> +        reg = KVM_IOC_CPUCFG(i);
>>>>>> +        if (put_user(reg, uindices++))
>>>>>> +            return -EFAULT;
>>>>>> +    }
>>>>>> +
>>>>>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>>>>>> +    if (put_user(reg, uindices++))
>>>>>> +        return -EFAULT;
>>>>>> +
>>>>>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>>>>>> +        return 0;
>>>>>> +
>>>>>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>>>>>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>>>>>> +        if (put_user(reg, uindices++))
>>>>>> +            return -EFAULT;
>>>>>> +    }
>>>>>> +
>>>>>> +    return 0;
>>>>>> +}
>>>>>> +
>>>>>>     long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>>                  unsigned int ioctl, unsigned long arg)
>>>>>>     {
>>>>>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>>             r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>>>>>             break;
>>>>>>         }
>>>>>> +    case KVM_GET_REG_LIST: {
>>>>>> +        struct kvm_reg_list __user *user_list = argp;
>>>>>> +        struct kvm_reg_list reg_list;
>>>>>> +        unsigned n;
>>>>>> +
>>>>>> +        r = -EFAULT;
>>>>>> +        if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
>>>>>> +            break;
>>>>>> +        n = reg_list.n;
>>>>>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>>>>>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>>>>>> +            break;
>>>>>> +        r = -E2BIG;
>>>>>> +        if (n < reg_list.n)
>>>>>> +            break;
>>>>>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>>>>>> +        break;
>>>>>> +    }
>>>>>>         default:
>>>>>>             r = -ENOIOCTLCMD;
>>>>>>             break;
>>>>>>
>>>>>
>>>> Thanks,
>>>> Zixing
>>>>
>>>
>> Thanks,
>> Zixing
>>
>
Thanks,

Zixing

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[Bibo Mao]

On 2026/1/26 下午4:54, liushuyu wrote:
> Hi Bibo,
> 
>>
>>
>> On 2026/1/26 下午12:22, liushuyu wrote:
>>> Hi Bibo,
>>>
>>>>
>>>>
>>>> On 2026/1/26 上午11:38, liushuyu wrote:
>>>>> Hi Bibo,
>>>>>>
>>>>>>
>>>>>> On 2026/1/25 下午1:43, Zixing Liu wrote:
>>>>>>> This ioctl can be used by userspace applications to determine which
>>>>>>> (special) registers are get/set-able.
>>>>>>>
>>>>>>> This can be very useful for cross-platform VMMs so that they do not
>>>>>>> have
>>>>>>> to hardcode register indices for each supported architectures.
>>>>>>>
>>>>>>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>>>>>>> ---
>>>>>>>
>>>>>>> For example, this ioctl could be used by rust-vmm/rust-kvm or maybe
>>>>>>> VirtualBox-kvm in the future.
>>>>>>>
>>>>>>>      Documentation/virt/kvm/api.rst |  2 +-
>>>>>>>      arch/loongarch/kvm/vcpu.c      | 69
>>>>>>> ++++++++++++++++++++++++++++++++++
>>>>>>>      2 files changed, 70 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/Documentation/virt/kvm/api.rst
>>>>>>> b/Documentation/virt/kvm/api.rst
>>>>>>> index 01a3abef8abb..f46dd8be282f 100644
>>>>>>> --- a/Documentation/virt/kvm/api.rst
>>>>>>> +++ b/Documentation/virt/kvm/api.rst
>>>>>>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>>>>>>      ---------------------
>>>>>>>        :Capability: basic
>>>>>>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>>>>>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if
>>>>>>> KVM_CAP_ONE_REG)
>>>>>>>      :Type: vcpu ioctl
>>>>>>>      :Parameters: struct kvm_reg_list (in/out)
>>>>>>>      :Returns: 0 on success; -1 on error
>>>>>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>>>>>> index 656b954c1134..b884eb9c76aa 100644
>>>>>>> --- a/arch/loongarch/kvm/vcpu.c
>>>>>>> +++ b/arch/loongarch/kvm/vcpu.c
>>>>>>> @@ -1186,6 +1186,57 @@ static int kvm_loongarch_vcpu_set_attr(struct
>>>>>>> kvm_vcpu *vcpu,
>>>>>>>          return ret;
>>>>>>>      }
>>>>>>>      +static unsigned long kvm_loongarch_num_lbt_regs(void)
>>>>>>> +{
>>>>>>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>>>>>>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long)
>>>>>>> + 1;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>>>>>>> +{
>>>>>>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>>>>>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>>>>>>> +
>>>>>>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>>>>>>> +        res += kvm_loongarch_num_lbt_regs();
>>>>>>> +
>>>>>>> +    return res;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>>>>>> +                      u64 __user *uindices)
>>>>>>> +{
>>>>>>> +    u64 reg;
>>>>>>> +    unsigned int i;
>>>>>>> +
>>>>>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>>>>>> +        reg = KVM_IOC_CSRID(i);
>>>>>>> +        if (put_user(reg, uindices++))
>>>>>>> +            return -EFAULT;
>>>>>>> +    }
>>>>>> CSR_MAX_NUMS is max number of accessible CSR registers, instead only
>>>>>> part of them is used by vCPU model. By my understanding, there
>>>>>> will be
>>>>>> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
>>>>>> better if real CSR register id and number is returned.
>>>>>>
>>>>> Did you mean we should only return the CSR registers initialized in
>>>>> this
>>>>> function
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
>>>>>
>>>>>
>>>>> ?
>>>>>
>>>>> That looks like a very large list and the values of the register
>>>>> IDs are
>>>>> not fully continuous. If that is the case, how do we maintain the
>>>>> get/set-able CSR register list?
>>>> It will be better if CSR register list can be categorized, for example
>>>> with LoongArch CPU manual CSR register is split into 8 types from
>>>> chapter 7.4 -- 7.11
>>>>
>>>> At the beginning, there is big array with size CSR_MAX_NUMS without
>>>> any category, it can be fine-gained in late.
>>>
>>> Does that mean in the new `kvm_loongarch_copy_reg_indices` function, it
>>> is also okay to embed this big list in there?
>> Firstly I do not know how to use ioctl command KVM_GET_REG_LIST in VMM
>> actually.
>>
>> At the second from the word "determine which (special) registers are
>> get/set-able", I think that it is better to set accessible CSR
>> register number and ID rather than the total number CSR_MAX_NUMS.
>>
> Understood. I will post a v2 patch, and we can continue the discussion
> from there to see if I understood your points correctly.
Remember to add such lines in function kvm_init_gcsr_flag() in the next 
round, since MSGINT CSR registers are missing here.

void kvm_init_gcsr_flag(void) {
+        if (cpu_has_msgint) {
+                set_gcsr_hw_flag(LOONGARCH_CSR_ISR0);
+                set_gcsr_hw_flag(LOONGARCH_CSR_ISR1);
+                set_gcsr_hw_flag(LOONGARCH_CSR_ISR2);
+                set_gcsr_hw_flag(LOONGARCH_CSR_ISR3);
+        }
}

Regards
Bibo Mao
> 
>> +static int kvm_loongarch_num_csr_regs(struct kvm_vcpu *vcpu)
>> +{
>> +    unsigned int i, count;
>> +
>> +    count = 0
>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>> +        if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
>> +            continue;
>> +        count++;
>> +    }
>> +    return count;
>> +}
>>
>> static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>> {
>>      /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>> +    unsigned long res = kvm_loongarch_num_csr_regs +
>> KVM_MAX_CPUCFG_REGS + 1;
>>
>>      if (kvm_guest_has_lbt(&vcpu->arch))
>>          res += kvm_loongarch_num_lbt_regs();
>>
>>      return res;
>> }
>>
>> static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>                        u64 __user *uindices)
>> {
>>      u64 reg;
>>      unsigned int i;
>>
>>      for (i = 0; i < CSR_MAX_NUMS; i++) {
>> +                if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
>> +                    continue;
>>          reg = KVM_IOC_CSRID(i);
>>          if (put_user(reg, uindices++))
>>              return -EFAULT;
>>      }
>>
>> Regards
>> Bibo Mao
>>>
>>> Or do you want to extract the list from the `kvm_init_gcsr_flag`
>>> function and refactor both functions to share one single big list
>>> (probably in the kvm_host.h header)?
>>>
>>> Because from what I could understand, your previous messages point to
>>> that we need to use this list to make out what CSR registers to return
>>> to the user space VMMs.
>>
>>>
>>>>
>>>> Regards
>>>> Bibo Mao
>>>>>
>>>>>> Regards
>>>>>> Bibo Mao
>>>>>>> +
>>>>>>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>>>>>>> +        reg = KVM_IOC_CPUCFG(i);
>>>>>>> +        if (put_user(reg, uindices++))
>>>>>>> +            return -EFAULT;
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>>>>>>> +    if (put_user(reg, uindices++))
>>>>>>> +        return -EFAULT;
>>>>>>> +
>>>>>>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>>>>>>> +        return 0;
>>>>>>> +
>>>>>>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>>>>>>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>>>>>>> +        if (put_user(reg, uindices++))
>>>>>>> +            return -EFAULT;
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>>      long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>>>                   unsigned int ioctl, unsigned long arg)
>>>>>>>      {
>>>>>>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>>>              r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>>>>>>              break;
>>>>>>>          }
>>>>>>> +    case KVM_GET_REG_LIST: {
>>>>>>> +        struct kvm_reg_list __user *user_list = argp;
>>>>>>> +        struct kvm_reg_list reg_list;
>>>>>>> +        unsigned n;
>>>>>>> +
>>>>>>> +        r = -EFAULT;
>>>>>>> +        if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
>>>>>>> +            break;
>>>>>>> +        n = reg_list.n;
>>>>>>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>>>>>>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>>>>>>> +            break;
>>>>>>> +        r = -E2BIG;
>>>>>>> +        if (n < reg_list.n)
>>>>>>> +            break;
>>>>>>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>>>>>>> +        break;
>>>>>>> +    }
>>>>>>>          default:
>>>>>>>              r = -ENOIOCTLCMD;
>>>>>>>              break;
>>>>>>>
>>>>>>
>>>>> Thanks,
>>>>> Zixing
>>>>>
>>>>
>>> Thanks,
>>> Zixing
>>>
>>
> Thanks,
> 
> Zixing
> 

Re: [PATCH 1/1] KVM: Add KVM_GET_REG_LIST ioctl for LoongArch

[liushuyu]

Hi Bibo,

>
>
> On 2026/1/26 下午4:54, liushuyu wrote:
>> Hi Bibo,
>>
>>>
>>>
>>> On 2026/1/26 下午12:22, liushuyu wrote:
>>>> Hi Bibo,
>>>>
>>>>>
>>>>>
>>>>> On 2026/1/26 上午11:38, liushuyu wrote:
>>>>>> Hi Bibo,
>>>>>>>
>>>>>>>
>>>>>>> On 2026/1/25 下午1:43, Zixing Liu wrote:
>>>>>>>> This ioctl can be used by userspace applications to determine
>>>>>>>> which
>>>>>>>> (special) registers are get/set-able.
>>>>>>>>
>>>>>>>> This can be very useful for cross-platform VMMs so that they do
>>>>>>>> not
>>>>>>>> have
>>>>>>>> to hardcode register indices for each supported architectures.
>>>>>>>>
>>>>>>>> Signed-off-by: Zixing Liu <liushuyu@aosc.io>
>>>>>>>> ---
>>>>>>>>
>>>>>>>> For example, this ioctl could be used by rust-vmm/rust-kvm or
>>>>>>>> maybe
>>>>>>>> VirtualBox-kvm in the future.
>>>>>>>>
>>>>>>>>      Documentation/virt/kvm/api.rst |  2 +-
>>>>>>>>      arch/loongarch/kvm/vcpu.c      | 69
>>>>>>>> ++++++++++++++++++++++++++++++++++
>>>>>>>>      2 files changed, 70 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/Documentation/virt/kvm/api.rst
>>>>>>>> b/Documentation/virt/kvm/api.rst
>>>>>>>> index 01a3abef8abb..f46dd8be282f 100644
>>>>>>>> --- a/Documentation/virt/kvm/api.rst
>>>>>>>> +++ b/Documentation/virt/kvm/api.rst
>>>>>>>> @@ -3603,7 +3603,7 @@ VCPU matching underlying host.
>>>>>>>>      ---------------------
>>>>>>>>        :Capability: basic
>>>>>>>> -:Architectures: arm64, mips, riscv, x86 (if KVM_CAP_ONE_REG)
>>>>>>>> +:Architectures: arm64, loongarch, mips, riscv, x86 (if
>>>>>>>> KVM_CAP_ONE_REG)
>>>>>>>>      :Type: vcpu ioctl
>>>>>>>>      :Parameters: struct kvm_reg_list (in/out)
>>>>>>>>      :Returns: 0 on success; -1 on error
>>>>>>>> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
>>>>>>>> index 656b954c1134..b884eb9c76aa 100644
>>>>>>>> --- a/arch/loongarch/kvm/vcpu.c
>>>>>>>> +++ b/arch/loongarch/kvm/vcpu.c
>>>>>>>> @@ -1186,6 +1186,57 @@ static int
>>>>>>>> kvm_loongarch_vcpu_set_attr(struct
>>>>>>>> kvm_vcpu *vcpu,
>>>>>>>>          return ret;
>>>>>>>>      }
>>>>>>>>      +static unsigned long kvm_loongarch_num_lbt_regs(void)
>>>>>>>> +{
>>>>>>>> +    /* +1 for the LBT_FTOP flag (inside arch.fpu) */
>>>>>>>> +    return sizeof(struct loongarch_lbt) / sizeof(unsigned long)
>>>>>>>> + 1;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu
>>>>>>>> *vcpu)
>>>>>>>> +{
>>>>>>>> +    /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>>>>>>> +    unsigned long res = CSR_MAX_NUMS + KVM_MAX_CPUCFG_REGS + 1;
>>>>>>>> +
>>>>>>>> +    if (kvm_guest_has_lbt(&vcpu->arch))
>>>>>>>> +        res += kvm_loongarch_num_lbt_regs();
>>>>>>>> +
>>>>>>>> +    return res;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>>>>>>> +                      u64 __user *uindices)
>>>>>>>> +{
>>>>>>>> +    u64 reg;
>>>>>>>> +    unsigned int i;
>>>>>>>> +
>>>>>>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>>>>>>> +        reg = KVM_IOC_CSRID(i);
>>>>>>>> +        if (put_user(reg, uindices++))
>>>>>>>> +            return -EFAULT;
>>>>>>>> +    }
>>>>>>> CSR_MAX_NUMS is max number of accessible CSR registers, instead
>>>>>>> only
>>>>>>> part of them is used by vCPU model. By my understanding, there
>>>>>>> will be
>>>>>>> no much meaning if CSR_MAX_NUMS is returned. And I think it will be
>>>>>>> better if real CSR register id and number is returned.
>>>>>>>
>>>>>> Did you mean we should only return the CSR registers initialized in
>>>>>> this
>>>>>> function
>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/loongarch/kvm/main.c?id=63804fed149a6750ffd28610c5c1c98cce6bd377#n48
>>>>>>
>>>>>>
>>>>>>
>>>>>> ?
>>>>>>
>>>>>> That looks like a very large list and the values of the register
>>>>>> IDs are
>>>>>> not fully continuous. If that is the case, how do we maintain the
>>>>>> get/set-able CSR register list?
>>>>> It will be better if CSR register list can be categorized, for
>>>>> example
>>>>> with LoongArch CPU manual CSR register is split into 8 types from
>>>>> chapter 7.4 -- 7.11
>>>>>
>>>>> At the beginning, there is big array with size CSR_MAX_NUMS without
>>>>> any category, it can be fine-gained in late.
>>>>
>>>> Does that mean in the new `kvm_loongarch_copy_reg_indices`
>>>> function, it
>>>> is also okay to embed this big list in there?
>>> Firstly I do not know how to use ioctl command KVM_GET_REG_LIST in VMM
>>> actually.
>>>
>>> At the second from the word "determine which (special) registers are
>>> get/set-able", I think that it is better to set accessible CSR
>>> register number and ID rather than the total number CSR_MAX_NUMS.
>>>
>> Understood. I will post a v2 patch, and we can continue the discussion
>> from there to see if I understood your points correctly.
> Remember to add such lines in function kvm_init_gcsr_flag() in the
> next round, since MSGINT CSR registers are missing here.
>
> void kvm_init_gcsr_flag(void) {
> +        if (cpu_has_msgint) {
> +                set_gcsr_hw_flag(LOONGARCH_CSR_ISR0);
> +                set_gcsr_hw_flag(LOONGARCH_CSR_ISR1);
> +                set_gcsr_hw_flag(LOONGARCH_CSR_ISR2);
> +                set_gcsr_hw_flag(LOONGARCH_CSR_ISR3);
> +        }
> } 
>
I think this might need to be a separate patch or commit.

Do you want me to include this in the KVM_GET_REG_LIST patch, or do you
want to submit this change separately?

> Regards
> Bibo Mao
>>
>>> +static int kvm_loongarch_num_csr_regs(struct kvm_vcpu *vcpu)
>>> +{
>>> +    unsigned int i, count;
>>> +
>>> +    count = 0
>>> +    for (i = 0; i < CSR_MAX_NUMS; i++) {
>>> +        if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
>>> +            continue;
>>> +        count++;
>>> +    }
>>> +    return count;
>>> +}
>>>
>>> static unsigned long kvm_loongarch_num_regs(struct kvm_vcpu *vcpu)
>>> {
>>>      /* +1 for the KVM_REG_LOONGARCH_COUNTER register */
>>> +    unsigned long res = kvm_loongarch_num_csr_regs +
>>> KVM_MAX_CPUCFG_REGS + 1;
>>>
>>>      if (kvm_guest_has_lbt(&vcpu->arch))
>>>          res += kvm_loongarch_num_lbt_regs();
>>>
>>>      return res;
>>> }
>>>
>>> static int kvm_loongarch_copy_reg_indices(struct kvm_vcpu *vcpu,
>>>                        u64 __user *uindices)
>>> {
>>>      u64 reg;
>>>      unsigned int i;
>>>
>>>      for (i = 0; i < CSR_MAX_NUMS; i++) {
>>> +                if (!(get_gcsr_flag(i) & (SW_GCSR | HW_GCSR)))
>>> +                    continue;
>>>          reg = KVM_IOC_CSRID(i);
>>>          if (put_user(reg, uindices++))
>>>              return -EFAULT;
>>>      }
>>>
>>> Regards
>>> Bibo Mao
>>>>
>>>> Or do you want to extract the list from the `kvm_init_gcsr_flag`
>>>> function and refactor both functions to share one single big list
>>>> (probably in the kvm_host.h header)?
>>>>
>>>> Because from what I could understand, your previous messages point to
>>>> that we need to use this list to make out what CSR registers to return
>>>> to the user space VMMs.
>>>
>>>>
>>>>>
>>>>> Regards
>>>>> Bibo Mao
>>>>>>
>>>>>>> Regards
>>>>>>> Bibo Mao
>>>>>>>> +
>>>>>>>> +    for (i = 0; i < KVM_MAX_CPUCFG_REGS; i++) {
>>>>>>>> +        reg = KVM_IOC_CPUCFG(i);
>>>>>>>> +        if (put_user(reg, uindices++))
>>>>>>>> +            return -EFAULT;
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>> +    reg = KVM_REG_LOONGARCH_COUNTER;
>>>>>>>> +    if (put_user(reg, uindices++))
>>>>>>>> +        return -EFAULT;
>>>>>>>> +
>>>>>>>> +    if (!kvm_guest_has_lbt(&vcpu->arch))
>>>>>>>> +        return 0;
>>>>>>>> +
>>>>>>>> +    for (i = 1; i <= kvm_loongarch_num_lbt_regs(); i++) {
>>>>>>>> +        reg = (KVM_REG_LOONGARCH_LBT | KVM_REG_SIZE_U64 | i);
>>>>>>>> +        if (put_user(reg, uindices++))
>>>>>>>> +            return -EFAULT;
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>> +    return 0;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>      long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>>>>                   unsigned int ioctl, unsigned long arg)
>>>>>>>>      {
>>>>>>>> @@ -1251,6 +1302,24 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>>>>>>>              r = kvm_loongarch_vcpu_set_attr(vcpu, &attr);
>>>>>>>>              break;
>>>>>>>>          }
>>>>>>>> +    case KVM_GET_REG_LIST: {
>>>>>>>> +        struct kvm_reg_list __user *user_list = argp;
>>>>>>>> +        struct kvm_reg_list reg_list;
>>>>>>>> +        unsigned n;
>>>>>>>> +
>>>>>>>> +        r = -EFAULT;
>>>>>>>> +        if (copy_from_user(&reg_list, user_list,
>>>>>>>> sizeof(reg_list)))
>>>>>>>> +            break;
>>>>>>>> +        n = reg_list.n;
>>>>>>>> +        reg_list.n = kvm_loongarch_num_regs(vcpu);
>>>>>>>> +        if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
>>>>>>>> +            break;
>>>>>>>> +        r = -E2BIG;
>>>>>>>> +        if (n < reg_list.n)
>>>>>>>> +            break;
>>>>>>>> +        r = kvm_loongarch_copy_reg_indices(vcpu, user_list->reg);
>>>>>>>> +        break;
>>>>>>>> +    }
>>>>>>>>          default:
>>>>>>>>              r = -ENOIOCTLCMD;
>>>>>>>>              break;
>>>>>>>>
>>>>>>>
>>>>>> Thanks,
>>>>>> Zixing
>>>>>>
>>>>>
>>>> Thanks,
>>>> Zixing
>>>>
>>>
>> Thanks,
>>
>> Zixing
>>
>
Thanks,

Zixing