Re: [PATCH v3 14/17] RISC-V: KVM: add SBI extension init()/deinit() functions

["Clément Léger" <cleger@rivosinc.com>]

On 13/03/2025 15:27, Andrew Jones wrote:
> On Mon, Mar 10, 2025 at 04:12:21PM +0100, Clément Léger wrote:
>> The FWFT SBI extension will need to dynamically allocate memory and do
>> init time specific initialization. Add an init/deinit callbacks that
>> allows to do so.
>>
>> Signed-off-by: Clément Léger <cleger@rivosinc.com>
>> ---
>>  arch/riscv/include/asm/kvm_vcpu_sbi.h |  9 +++++++++
>>  arch/riscv/kvm/vcpu.c                 |  2 ++
>>  arch/riscv/kvm/vcpu_sbi.c             | 29 +++++++++++++++++++++++++++
>>  3 files changed, 40 insertions(+)
>>
>> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> index 4ed6203cdd30..bcb90757b149 100644
>> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> @@ -49,6 +49,14 @@ struct kvm_vcpu_sbi_extension {
>>  
>>  	/* Extension specific probe function */
>>  	unsigned long (*probe)(struct kvm_vcpu *vcpu);
>> +
>> +	/*
>> +	 * Init/deinit function called once during VCPU init/destroy. These
>> +	 * might be use if the SBI extensions need to allocate or do specific
>> +	 * init time only configuration.
>> +	 */
>> +	int (*init)(struct kvm_vcpu *vcpu);
>> +	void (*deinit)(struct kvm_vcpu *vcpu);
>>  };
>>  
>>  void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> @@ -69,6 +77,7 @@ const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
>>  bool riscv_vcpu_supports_sbi_ext(struct kvm_vcpu *vcpu, int idx);
>>  int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);
>>  void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
>> +void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
>>  
>>  int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
>>  				   unsigned long *reg_val);
>> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
>> index 60d684c76c58..877bcc85c067 100644
>> --- a/arch/riscv/kvm/vcpu.c
>> +++ b/arch/riscv/kvm/vcpu.c
>> @@ -185,6 +185,8 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
>>  
>>  void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>>  {
>> +	kvm_riscv_vcpu_sbi_deinit(vcpu);
>> +
>>  	/* Cleanup VCPU AIA context */
>>  	kvm_riscv_vcpu_aia_deinit(vcpu);
>>  
>> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
>> index d1c83a77735e..858ddefd7e7f 100644
>> --- a/arch/riscv/kvm/vcpu_sbi.c
>> +++ b/arch/riscv/kvm/vcpu_sbi.c
>> @@ -505,8 +505,37 @@ void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu)
>>  			continue;
>>  		}
>>  
>> +		if (!ext->default_disabled && ext->init &&
>> +		    ext->init(vcpu) != 0) {
>> +			scontext->ext_status[idx] = KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
>> +			continue;
>> +		}
> 
> I think this new block should be below the assignment below (and it can
> drop the continue) and it shouldn't check default_disabled (as I've done
> below). IOW, we should always run ext->init when there is one to run here.
> Otherwise, I how will it get run later?

Ok, i did not saw that there was a possibility to enable the extension
at a later time. I'll fix that.

Thanks,

Clément

> 
>> +
>>  		scontext->ext_status[idx] = ext->default_disabled ?
>>  					KVM_RISCV_SBI_EXT_STATUS_DISABLED :
>>  					KVM_RISCV_SBI_EXT_STATUS_ENABLED;
> 
>                 if (ext->init && ext->init(vcpu))
>                     scontext->ext_status[idx] = KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
> 
>>  	}
>>  }
>> +
>> +void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu)
>> +{
>> +	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
>> +	const struct kvm_riscv_sbi_extension_entry *entry;
>> +	const struct kvm_vcpu_sbi_extension *ext;
>> +	int idx, i;
>> +
>> +	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
>> +		entry = &sbi_ext[i];
>> +		ext = entry->ext_ptr;
>> +		idx = entry->ext_idx;
>> +
>> +		if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
>> +			continue;
>> +
>> +		if (scontext->ext_status[idx] == KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE ||
>> +		    !ext->deinit)
>> +			continue;
>> +
>> +		ext->deinit(vcpu);
>> +	}
>> +}
>> -- 
>> 2.47.2
>>
> 
> Thanks,
> drew