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

[Huacai Chen]

Hi, Bibo,

On Mon, Jul 27, 2026 at 3:29 PM Bibo Mao <maobibo@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> ---
>  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?

> +
>         /* 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".


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
>