Re: [PATCH v3 0/3] LoongArch: KVM: Add separate vmid support

[Huacai Chen]

Applied, thanks.


Huacai

On Mon, Aug 31, 2026 at 5:54 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. There are such advantages if separated vmid
> is supported.
>   1. One VM uses one vmid, vCPUs on the same VM can share the same vmid.
>   2. If one vCPU switch between different physical CPUs, old vmid can be
>      still useful if it is not expired.
>   3. For remote tlb flush, it is to flush TLBs which are mapping
>      GPA --> HPA, only vmid need update and vpid need not.
>
> Here add separate vmid feature support, vmid feature detecting method
> comes from CPUCFG8 capability when LVZ is enabled.
> ---
> v2 ... v3:
>   1. Merge patch 1-2 into one and patch 3-4 into one.
>   2. Return directly and do not update vmid in function __kvm_check_vmid()
>      if feature cpu_has_guestid is disabled by AI agent review.
>   3. In function kvm_arch_disable_virtualization_cpu disable feature
>      CSR_GTLBC_USES2TGID, similiar with enable cpu virtualization,
>      the same from AI agent review.
>   4. Rename USEVMID with USES2TGID, VMID is KVM software word and S2TGID
>      is hardware word.
>   5. Set cpu bit with vcpu->kvm->arch.tlb_flush_pending with
>      KVM_REQ_TLB_FLUSH, similiar with request KVM_REQ_TLB_FLUSH_GPA.
>
> v1 ... v2:
>   1. Move vmid together with vpid in patch1, rename it with hw_vmid.
>   2. Rename kvm_check_vcpuid() with __kvm_check_vpid(), and function
>      kvm_check_vmid() with __kvm_check_vmid().
>   3. Merge part of patch 2, patch 3/4 together.
>   4. Use bit8 of CPUCFG8 as guestid capability rather than LVZ version,
>      since it is hard to decide whether this feature exists with high LVZ
>      version in future.
>   5. Set cpu bit with vcpu->kvm->arch.tlb_flush_pending rather than
>      using add request KVM_REQ_TLB_FLUSH_GPA, it needs flush TLB on CPU
>      where page fault happens and vCPU maybe migrates to other CPUs.
> ---
> Bibo Mao (3):
>   LoongArch: KVM: Add vmid support for stage2 MMU
>   LoongArch: KVM: Implement vmid updating logic
>   LoongArch: KVM: Enable separate vmid feature
>
>  arch/loongarch/include/asm/kvm_host.h  | 10 ++++
>  arch/loongarch/include/asm/loongarch.h |  5 ++
>  arch/loongarch/kernel/asm-offsets.c    |  1 +
>  arch/loongarch/kernel/cpu-probe.c      |  6 +++
>  arch/loongarch/kvm/main.c              | 71 ++++++++++++++++++++++++--
>  arch/loongarch/kvm/mmu.c               | 30 +++++++++--
>  arch/loongarch/kvm/switch.S            |  5 +-
>  arch/loongarch/kvm/tlb.c               | 19 ++++++-
>  8 files changed, 135 insertions(+), 12 deletions(-)
>
>
> base-commit: 73e3f0710014fe6d4ed98cfc02292f6121db7558
> --
> 2.39.3
>