Re: [PATCH 1/6] LoongArch: KVM: Add vmid support for stage2 MMU

[Bibo Mao <maobibo@loongson.cn>]

On 2026/8/2 下午10:11, Huacai Chen wrote:
> Hi, Bibo,
> 
> On Mon, Jul 27, 2026 at 3:29 PM Bibo Mao <maobibo@loongson.cn> wrote:
>>
>> LoongArch KVM hypervisor supports two-level MMU, vpid index is used
>> for stage1 MMU and vmid index is used for stage2 MMU.
>>
>> On 3A5000, vmid must be the same with vpid. On 3A6000 platform vmid
>> may separate from vpid. If vcpu migrate to different physical CPUs,
>> vpid need change however vmid can keep the same with old value. Also
>> vmid index of the while VM machine on physical CPU the same, all vCPUs
>> on the VM can share the same vmid index on one physical CPU.
>>
>> Here vmid index is added and it keeps the same with vpid still.
>>
>> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
>> ---
>>   arch/loongarch/include/asm/kvm_host.h | 3 +++
>>   arch/loongarch/kernel/asm-offsets.c   | 1 +
>>   arch/loongarch/kvm/main.c             | 1 +
>>   arch/loongarch/kvm/switch.S           | 5 ++---
>>   arch/loongarch/kvm/tlb.c              | 5 ++++-
>>   5 files changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
>> index 23cfbecebbd7..ec7b0c402385 100644
>> --- a/arch/loongarch/include/asm/kvm_host.h
>> +++ b/arch/loongarch/include/asm/kvm_host.h
>> @@ -189,6 +189,9 @@ struct kvm_vcpu_arch {
>>          unsigned long host_tp;
>>          unsigned long host_pgd;
>>
>> +       /* vmid info for guest VM */
>> +       unsigned long vmid;
> Put it near vpid?
yes, it it better to near vpid. will do this.
> 
>> +
>>          /* Host CSRs are used when handling exits from guest */
>>          unsigned long badi;
>>          unsigned long badv;
>> diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
>> index 1b861cbc5e10..32ef6adfc8dd 100644
>> --- a/arch/loongarch/kernel/asm-offsets.c
>> +++ b/arch/loongarch/kernel/asm-offsets.c
>> @@ -300,6 +300,7 @@ static void __used output_kvm_defines(void)
>>          OFFSET(KVM_ARCH_HSP, kvm_vcpu_arch, host_sp);
>>          OFFSET(KVM_ARCH_HTP, kvm_vcpu_arch, host_tp);
>>          OFFSET(KVM_ARCH_HPGD, kvm_vcpu_arch, host_pgd);
>> +       OFFSET(KVM_ARCH_VMID, kvm_vcpu_arch, vmid);
>>          OFFSET(KVM_ARCH_KVMPGD, kvm_vcpu_arch, kvm_pgd);
>>          OFFSET(KVM_ARCH_HANDLE_EXIT, kvm_vcpu_arch, handle_exit);
>>          OFFSET(KVM_ARCH_HEENTRY, kvm_vcpu_arch, host_eentry);
>> diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
>> index 3e1005526f4b..6e3e8efa1dc2 100644
>> --- a/arch/loongarch/kvm/main.c
>> +++ b/arch/loongarch/kvm/main.c
>> @@ -223,6 +223,7 @@ static void kvm_update_vpid(struct kvm_vcpu *vcpu, int cpu)
>>
>>          context->vpid_cache = vpid;
>>          vcpu->arch.vpid = vpid;
>> +       vcpu->arch.vmid = vcpu->arch.vpid & vpid_mask;
> 
> I think both vpid and vmid need "& vpid_mask".
vpid used in function kvm_check_vcpuid() includes version information 
also. vmid here is hardware id directly used by LOONGARCH_CSR_GTLBC in 
arch/loongarch/kvm/switch.S.

Regards
Bibo Mao
> 
> 
> Huacai
> 
>>   }
>>
>>   void kvm_check_vpid(struct kvm_vcpu *vcpu)
>> diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
>> index 936e4ae3e408..af972394fd55 100644
>> --- a/arch/loongarch/kvm/switch.S
>> +++ b/arch/loongarch/kvm/switch.S
>> @@ -66,9 +66,8 @@
>>          ld.d    t0, a2, KVM_ARCH_KVMPGD
>>          csrwr   t0, LOONGARCH_CSR_PGDL
>>
>> -       /* Mix GID and RID */
>> -       csrrd           t1, LOONGARCH_CSR_GSTAT
>> -       bstrpick.w      t1, t1, CSR_GSTAT_GID_SHIFT_END, CSR_GSTAT_GID_SHIFT
>> +       /* Set VMID for gpa --> hpa mapping */
>> +       ld.d            t1, a2, KVM_ARCH_VMID
>>          csrrd           t0, LOONGARCH_CSR_GTLBC
>>          bstrins.w       t0, t1, CSR_GTLBC_TGID_SHIFT_END, CSR_GTLBC_TGID_SHIFT
>>          csrwr           t0, LOONGARCH_CSR_GTLBC
>> diff --git a/arch/loongarch/kvm/tlb.c b/arch/loongarch/kvm/tlb.c
>> index ebdbe9264e9c..38daf936021d 100644
>> --- a/arch/loongarch/kvm/tlb.c
>> +++ b/arch/loongarch/kvm/tlb.c
>> @@ -23,7 +23,10 @@ void kvm_flush_tlb_all(void)
>>
>>   void kvm_flush_tlb_gpa(struct kvm_vcpu *vcpu, unsigned long gpa)
>>   {
>> +       unsigned int vmid;
>> +
>>          lockdep_assert_irqs_disabled();
>>          gpa &= (PAGE_MASK << 1);
>> -       invtlb(INVTLB_GID_ADDR, read_csr_gstat() & CSR_GSTAT_GID, gpa);
>> +       vmid = (vcpu->arch.vmid << CSR_GSTAT_GID_SHIFT) & CSR_GSTAT_GID;
>> +       invtlb(INVTLB_GID_ADDR, vmid, gpa);
>>   }
>> --
>> 2.39.3
>>