On Wed, 2025-03-26 at 19:36 +0000, Yosry Ahmed wrote:
> svm_flush_tlb_asid() currently operates on the current VMCB. In
> preparation for properly tracking TLB flushes for L1 and L2 ASIDs,
> refactor it to take is_guest_mode and find the proper VMCB. All existing
> callers pass is_guest_mode(vcpu) to maintain existing behavior for now.
>
> Move the comment about only flushing the current ASID to
> svm_flush_tlb_all(), where it probably should have been anyway, because
> svm_flush_tlb_asid() now flushes a given ASID, not the current ASID.
>
> Create a svm_flush_tlb_guest() wrapper to use as the flush_tlb_guest()
> callback.
>
> No functional change intended.
>
> Signed-off-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
> ---
> arch/x86/kvm/svm/svm.c | 39 +++++++++++++++++++++++++--------------
> 1 file changed, 25 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 865c5ce4fa473..fb6b9f88a1504 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4016,25 +4016,24 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu)
> svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
> }
>
> -static void svm_flush_tlb_asid(struct kvm_vcpu *vcpu)
> +static struct vmcb *svm_get_vmcb(struct vcpu_svm *svm, bool is_guest_mode)
> +{
> + return is_guest_mode ? svm->nested.vmcb02.ptr : svm->vmcb01.ptr;
> +}
Not sure 100% about this helper, it name might be a bit confusing because
we already have a current vmcb. Maybe add a comment above stating this
this is to get vmcb which might not be currently active?
> +
> +static void svm_flush_tlb_asid(struct kvm_vcpu *vcpu, bool is_guest_mode)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
> + struct vmcb *vmcb = svm_get_vmcb(svm, is_guest_mode);
>
> /*
> * Unlike VMX, SVM doesn't provide a way to flush only NPT TLB entries.
> * A TLB flush for the current ASID flushes both "host" and "guest" TLB
> * entries, and thus is a superset of Hyper-V's fine grained flushing.
> */
> - kvm_hv_vcpu_purge_flush_tlb(vcpu, is_guest_mode(vcpu));
> -
> - /*
> - * Flush only the current ASID even if the TLB flush was invoked via
> - * kvm_flush_remote_tlbs(). Although flushing remote TLBs requires all
> - * ASIDs to be flushed, KVM uses a single ASID for L1 and L2, and
> - * unconditionally does a TLB flush on both nested VM-Enter and nested
> - * VM-Exit (via kvm_mmu_reset_context()).
> - */
> - vmcb_set_flush_asid(svm->vmcb);
> + kvm_hv_vcpu_purge_flush_tlb(vcpu, is_guest_mode);
> + if (vmcb)
> + vmcb_set_flush_asid(vmcb);
> }
>
> static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
> @@ -4050,7 +4049,7 @@ static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
> if (svm_hv_is_enlightened_tlb_enabled(vcpu) && VALID_PAGE(root_tdp))
> hyperv_flush_guest_mapping(root_tdp);
>
> - svm_flush_tlb_asid(vcpu);
> + svm_flush_tlb_asid(vcpu, is_guest_mode(vcpu));
> }
>
> static void svm_flush_tlb_all(struct kvm_vcpu *vcpu)
> @@ -4065,7 +4064,14 @@ static void svm_flush_tlb_all(struct kvm_vcpu *vcpu)
> if (WARN_ON_ONCE(svm_hv_is_enlightened_tlb_enabled(vcpu)))
> hv_flush_remote_tlbs(vcpu->kvm);
>
> - svm_flush_tlb_asid(vcpu);
> + /*
> + * Flush only the current ASID even if the TLB flush was invoked via
> + * kvm_flush_remote_tlbs(). Although flushing remote TLBs requires all
> + * ASIDs to be flushed, KVM uses a single ASID for L1 and L2, and
> + * unconditionally does a TLB flush on both nested VM-Enter and nested
> + * VM-Exit (via kvm_mmu_reset_context()).
> + */
> + svm_flush_tlb_asid(vcpu, is_guest_mode(vcpu));
> }
>
> static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva)
> @@ -4075,6 +4081,11 @@ static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva)
> invlpga(gva, svm_get_current_asid(svm));
> }
>
> +static void svm_flush_tlb_guest(struct kvm_vcpu *vcpu)
> +{
> + svm_flush_tlb_asid(vcpu, is_guest_mode(vcpu));
> +}
> +
> static inline void sync_cr8_to_lapic(struct kvm_vcpu *vcpu)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
> @@ -5187,7 +5198,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
> .flush_tlb_all = svm_flush_tlb_all,
> .flush_tlb_current = svm_flush_tlb_current,
> .flush_tlb_gva = svm_flush_tlb_gva,
> - .flush_tlb_guest = svm_flush_tlb_asid,
> + .flush_tlb_guest = svm_flush_tlb_guest,
>
> .vcpu_pre_run = svm_vcpu_pre_run,
> .vcpu_run = svm_vcpu_run,
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
