Re: [PATCH] KVM: SVM: Flush Hyper-V TLB when required

On Fri, Mar 24, 2023, Jeremi Piotrowski wrote:

I have the #ifdef version ready to send out, but what do you think about this:

Oh, nice! Yeah, that works, I didn't see the stub for hyperv_flush_guest_mapping().

@@ -3753,6 +3753,39 @@ static void svm_flush_tlb_current(struct kvm_vcpu *vcpu) svm->current_vmcb->asid_generation--; } +static void svm_flush_tlb_current(struct kvm_vcpu *vcpu) +{

• hpa_t root_tdp = vcpu->arch.mmu->root.hpa;
• /*

• * When running on Hyper-V with EnlightenedNptTlb enabled, explicitly
  

• * flush the NPT mappings via hypercall as flushing the ASID only
  

• * affects virtual to physical mappings, it does not invalidate guest
  

• * physical to host physical mappings.
  

• */
  

• if (IS_ENABLED(CONFIG_HYPERV) &&

No need for the IS_ENABLED(CONFIG_HYPERV) check here, the svm_hv_is_enlightened_tlb_enabled() stub that's provided for CONFIG_HYPERV=n will guard this properly

if (svm_hv_is_enlightened_tlb_enabled(vcpu) && VALID_PAGE(root_tdp)) hyperv_flush_guest_mapping(root_tdp);

•    svm_hv_is_enlightened_tlb_enabled(vcpu) &&
  

•    VALID_PAGE(root_tdp))
  

• hyperv_flush_guest_mapping(root_tdp);
  

• svm_flush_tlb_asid(vcpu);

+}

+static void svm_flush_tlb_all(struct kvm_vcpu *vcpu) +{

• /*

• * When running on Hyper-V with EnlightenedNptTlb enabled, remote TLB
  

• * flushes should be routed to hv_remote_flush_tlb() without requesting
  

• * a "regular" remote flush.  Reaching this point means either there's
  

• * a KVM bug or a prior hv_remote_flush_tlb() call failed, both of
  

• * which might be fatal to the guest.  Yell, but try to recover.
  

• */
  

• if (IS_ENABLED(CONFIG_HYPERV) && WARN_ON_ONCE(svm_hv_is_enlightened_tlb_enabled(vcpu)))

• hv_remote_flush_tlb(vcpu->kvm);
  

And then

if (WARN_ON_ONCE(svm_hv_is_enlightened_tlb_enabled(vcpu))) hv_remote_flush_tlb(vcpu->kvm);

• svm_flush_tlb_asid(vcpu);

+}

static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva) { struct vcpu_svm *svm = to_svm(vcpu); @@ -4745,10 +4778,10 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { .set_rflags = svm_set_rflags, .get_if_flag = svm_get_if_flag,

• .flush_tlb_all = svm_flush_tlb_current,

• .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_current,

• .flush_tlb_guest = svm_flush_tlb_asid,

.vcpu_pre_run = svm_vcpu_pre_run, .vcpu_run = svm_vcpu_run, diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h index cff838f15db5..4c9e0d4ba3dd 100644 --- a/arch/x86/kvm/svm/svm_onhyperv.h +++ b/arch/x86/kvm/svm/svm_onhyperv.h @@ -6,6 +6,8 @@ #ifndef __ARCH_X86_KVM_SVM_ONHYPERV_H__ #define __ARCH_X86_KVM_SVM_ONHYPERV_H__

+#include <asm/mshyperv.h>

#if IS_ENABLED(CONFIG_HYPERV)

#include "kvm_onhyperv.h" @@ -15,6 +17,14 @@ static struct kvm_x86_ops svm_x86_ops; int svm_hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu); +static inline bool svm_hv_is_enlightened_tlb_enabled(struct kvm_vcpu *vcpu) +{

• struct hv_vmcb_enlightenments *hve = &to_svm(vcpu)->vmcb->control.hv_enlightenments;
• return ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB &&

• !!hve->hv_enlightenments_control.enlightened_npt_tlb;
  

Uber nit, align the indentation (7 spaces instead of 1 tab):

return ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB && !!hve->hv_enlightenments_control.enlightened_npt_tlb;