Re: [PATCH v11 09/46] KVM: x86: hyper-v: Introduce TLB flush fifo

Sean Christopherson
2022-10-19T19:52:34Z

On Tue, Oct 04, 2022, Vitaly Kuznetsov wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0539d216f760..7fb8bd42b13e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3388,7 +3388,7 @@ static void kvm_vcpu_flush_tlb_all(struct kvm_vcpu *vcpu)
> kvm_clear_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
> }
>
> -static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)
> +void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)

kvm_vcpu_flush_tlb_guest() doesn't need to be exposed in this patch, i.e. can
remain static. I think it can be restricted to x86.c even in the final form
(will follow-up in later patch).

> {
> ++vcpu->stat.tlb_flush;
>
> @@ -3409,7 +3409,7 @@ static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)
> * Flushing all "guest" TLB is always a superset of Hyper-V's fine
> * grained flushing.
> */
> - kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> + kvm_hv_vcpu_purge_flush_tlb(vcpu);
> }
>
>
> @@ -10484,7 +10484,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>
> kvm_service_local_tlb_flush_requests(vcpu);
>
> - if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
> + /*
> + * Fall back to a "full" guest flush if Hyper-V's precise
> + * flushing fails. Note, Hyper-V's flushing is per-vCPU, but
> + * the flushes are considered "remote" and not "local" because
> + * the requests can be initiated from other vCPUs.
> + */
> + if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu) &&
> + kvm_hv_vcpu_flush_tlb(vcpu))
> kvm_vcpu_flush_tlb_guest(vcpu);
>
> if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index a784ff90740b..1ea28a7bdf2f 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -79,6 +79,7 @@ static inline unsigned int __shrink_ple_window(unsigned int val,
>
> #define MSR_IA32_CR_PAT_DEFAULT 0x0007040600070406ULL
>
> +void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu);

As above, this is unnecessary.

> void kvm_service_local_tlb_flush_requests(struct kvm_vcpu *vcpu);
> int kvm_check_nested_events(struct kvm_vcpu *vcpu);
>
> --
> 2.37.3
>