Re: [PATCH 4/6] LoongArch: KVM: implement vmid updating logic

Hi, BIbo,

On Mon, Jul 27, 2026 at 3:30=E2=80=AFPM Bibo Mao <[email protected]> wrot=
e:
>
> For every physical CPU, there is one vmid calculation method. For
> vCPUs on the same VM, vmid is the same. However for vCPUs on
> different VM, vmid is different. When vCPU is scheduled on the
> physical CPU, it checked vmid of this VM and the global cached
> vmid, and judge whether it is valid or not.
I think Patch#2/3/4 can be folded into one.


Huacai

>
> Signed-off-by: Bibo Mao <[email protected]>
> ---
>  arch/loongarch/include/asm/kvm_host.h |  2 ++
>  arch/loongarch/kvm/main.c             | 42 ++++++++++++++++++++++++++-
>  2 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/inclu=
de/asm/kvm_host.h
> index e93307cbe740..a01623c42c7a 100644
> --- a/arch/loongarch/include/asm/kvm_host.h
> +++ b/arch/loongarch/include/asm/kvm_host.h
> @@ -79,6 +79,7 @@ struct kvm_arch_memory_slot {
>  #define HOST_MAX_PMNUM                 16
>  struct kvm_context {
>         unsigned long vpid_cache;
> +       unsigned long vmid_cache;
>         struct kvm_vcpu *last_vcpu;
>         /* Host PMU CSR */
>         u64 perf_ctrl[HOST_MAX_PMNUM];
> @@ -132,6 +133,7 @@ struct kvm_arch {
>         unsigned long kvm_features;
>
>         s64 time_offset;
> +       unsigned long vmid[NR_CPUS];
>         struct kvm_context __percpu *vmcs;
>         struct loongarch_ipi *ipi;
>         struct loongarch_dmsintc *dmsintc;
> diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
> index 3df46e02594f..7b3661da8958 100644
> --- a/arch/loongarch/kvm/main.c
> +++ b/arch/loongarch/kvm/main.c
> @@ -281,9 +281,33 @@ static void kvm_check_vcpuid(struct kvm_vcpu *vcpu)
>         }
>  }
>
> -static void kvm_check_vmid(struct kvm_vcpu *vcpu)
> +static void kvm_update_vmid(struct kvm_vcpu *vcpu, int cpu)
>  {
>         unsigned long vmid;
> +       struct kvm_context *context;
> +
> +       context =3D per_cpu_ptr(vcpu->kvm->arch.vmcs, cpu);
> +       vmid =3D context->vmid_cache + 1;
> +       if (!(vmid & vpid_mask)) {
> +               /* finish round of vmid loop */
> +               if (unlikely(!vmid))
> +                       vmid =3D vpid_mask + 1;
> +
> +               ++vmid; /* vmid 0 reserved for root */
> +
> +               /* start new vmid cycle */
> +               kvm_flush_tlb_all_stage2();
> +       }
> +
> +       context->vmid_cache =3D vmid;
> +       vcpu->kvm->arch.vmid[cpu] =3D vmid;
> +}
> +
> +static void kvm_check_vmid(struct kvm_vcpu *vcpu)
> +{
> +       int cpu;
> +       unsigned long ver, old, vmid;
> +       struct kvm_context *context;
>
>         /* On some machines like 3A5000, vmid needs the same with vpid */
>         if (!cpu_has_guestid) {
> @@ -295,6 +319,21 @@ static void kvm_check_vmid(struct kvm_vcpu *vcpu)
>
>                 return;
>         }
> +
> +       cpu =3D smp_processor_id();
> +       context =3D per_cpu_ptr(vcpu->kvm->arch.vmcs, cpu);
> +
> +       /*
> +        * Check if our vmid is of an older version
> +        */
> +       ver =3D vcpu->kvm->arch.vmid[cpu] & ~vpid_mask;
> +       old =3D context->vmid_cache & ~vpid_mask;
> +       if (ver !=3D old) {
> +               kvm_update_vmid(vcpu, cpu);
> +               kvm_clear_request(KVM_REQ_TLB_FLUSH_GPA, vcpu);
> +       }
> +
> +       vcpu->arch.vmid =3D vcpu->kvm->arch.vmid[cpu] & vpid_mask;
>  }
>
>  void kvm_check_vpid(struct kvm_vcpu *vcpu)
> @@ -400,6 +439,7 @@ static int kvm_loongarch_env_init(void)
>         for_each_possible_cpu(cpu) {
>                 context =3D per_cpu_ptr(vmcs, cpu);
>                 context->vpid_cache =3D vpid_mask + 1;
> +               context->vmid_cache =3D vpid_mask + 1;
>                 context->last_vcpu =3D NULL;
>         }
>
> --
> 2.39.3
>