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

[Huacai Chen]

On Mon, Aug 3, 2026 at 9:21 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
>
>
>
> 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@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?
> 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.
I'm not sure, but it seems both vpid and vmid have a sw version and a
hw version? The hw version will be written into register so its width
is limited, while the sw version is 64bit. If I'm right, I think the
"& vpid_mask" is only used when writing registers, in other places
they are full 64bit (in other words, they need the same treatment).

Huacai

>
> 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
> >>
>