| Message ID | 20201020215613.8972-2-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,01/10] KVM: VMX: Track common EPTP for Hyper-V's paravirt TLB flush | expand |
Sean Christopherson <sean.j.christopherson@intel.com> writes: > Explicitly track the EPTP that is common to all vCPUs instead of > grabbing vCPU0's EPTP when invoking Hyper-V's paravirt TLB flush. > Tracking the EPTP will allow optimizing the checks when loading a new > EPTP and will also allow dropping ept_pointer_match, e.g. by marking > the common EPTP as invalid. > > This also technically fixes a bug where KVM could theoretically flush an > invalid GPA if all vCPUs have an invalid root. In practice, it's likely > impossible to trigger a remote TLB flush in such a scenario. In any > case, the superfluous flush is completely benign. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/kvm/vmx/vmx.c | 19 ++++++++----------- > arch/x86/kvm/vmx/vmx.h | 1 + > 2 files changed, 9 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index bcc097bb8321..6d53bcc4a1a9 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -486,6 +486,7 @@ static void check_ept_pointer_match(struct kvm *kvm) > } > } > > + to_kvm_vmx(kvm)->hv_tlb_eptp = tmp_eptp; I was going to suggest you reset hv_tlb_eptp to INVALID_PAGE in case this check fails (couple lines above) but this function is gone later in the series and the replacement code in hv_remote_flush_tlb_with_range() does exactly that. > to_kvm_vmx(kvm)->ept_pointers_match = EPT_POINTERS_MATCH; > } > > @@ -498,21 +499,18 @@ static int kvm_fill_hv_flush_list_func(struct hv_guest_mapping_flush_list *flush > range->pages); > } > > -static inline int __hv_remote_flush_tlb_with_range(struct kvm *kvm, > - struct kvm_vcpu *vcpu, struct kvm_tlb_range *range) > +static inline int hv_remote_flush_eptp(u64 eptp, struct kvm_tlb_range *range) > { > - u64 ept_pointer = to_vmx(vcpu)->ept_pointer; > - > /* > * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs address > * of the base of EPT PML4 table, strip off EPT configuration > * information. > */ > if (range) > - return hyperv_flush_guest_mapping_range(ept_pointer & PAGE_MASK, > + return hyperv_flush_guest_mapping_range(eptp & PAGE_MASK, > kvm_fill_hv_flush_list_func, (void *)range); > else > - return hyperv_flush_guest_mapping(ept_pointer & PAGE_MASK); > + return hyperv_flush_guest_mapping(eptp & PAGE_MASK); > } > > static int hv_remote_flush_tlb_with_range(struct kvm *kvm, > @@ -530,12 +528,11 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm, > kvm_for_each_vcpu(i, vcpu, kvm) { > /* If ept_pointer is invalid pointer, bypass flush request. */ > if (VALID_PAGE(to_vmx(vcpu)->ept_pointer)) > - ret |= __hv_remote_flush_tlb_with_range( > - kvm, vcpu, range); > + ret |= hv_remote_flush_eptp(to_vmx(vcpu)->ept_pointer, > + range); > } > - } else { > - ret = __hv_remote_flush_tlb_with_range(kvm, > - kvm_get_vcpu(kvm, 0), range); > + } else if (VALID_PAGE(to_kvm_vmx(kvm)->hv_tlb_eptp)) { > + ret = hv_remote_flush_eptp(to_kvm_vmx(kvm)->hv_tlb_eptp, range); I assume Hyper-V will swallow IVALID_PAGE without complaining much but it seems pointless to do anything in this case indeed. > } > > spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock); > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index 5961cb897125..3d557a065c01 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -301,6 +301,7 @@ struct kvm_vmx { > bool ept_identity_pagetable_done; > gpa_t ept_identity_map_addr; > > + hpa_t hv_tlb_eptp; > enum ept_pointers_status ept_pointers_match; > spinlock_t ept_pointer_lock; > }; Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index bcc097bb8321..6d53bcc4a1a9 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -486,6 +486,7 @@ static void check_ept_pointer_match(struct kvm *kvm) } } + to_kvm_vmx(kvm)->hv_tlb_eptp = tmp_eptp; to_kvm_vmx(kvm)->ept_pointers_match = EPT_POINTERS_MATCH; } @@ -498,21 +499,18 @@ static int kvm_fill_hv_flush_list_func(struct hv_guest_mapping_flush_list *flush range->pages); } -static inline int __hv_remote_flush_tlb_with_range(struct kvm *kvm, - struct kvm_vcpu *vcpu, struct kvm_tlb_range *range) +static inline int hv_remote_flush_eptp(u64 eptp, struct kvm_tlb_range *range) { - u64 ept_pointer = to_vmx(vcpu)->ept_pointer; - /* * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs address * of the base of EPT PML4 table, strip off EPT configuration * information. */ if (range) - return hyperv_flush_guest_mapping_range(ept_pointer & PAGE_MASK, + return hyperv_flush_guest_mapping_range(eptp & PAGE_MASK, kvm_fill_hv_flush_list_func, (void *)range); else - return hyperv_flush_guest_mapping(ept_pointer & PAGE_MASK); + return hyperv_flush_guest_mapping(eptp & PAGE_MASK); } static int hv_remote_flush_tlb_with_range(struct kvm *kvm, @@ -530,12 +528,11 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm, kvm_for_each_vcpu(i, vcpu, kvm) { /* If ept_pointer is invalid pointer, bypass flush request. */ if (VALID_PAGE(to_vmx(vcpu)->ept_pointer)) - ret |= __hv_remote_flush_tlb_with_range( - kvm, vcpu, range); + ret |= hv_remote_flush_eptp(to_vmx(vcpu)->ept_pointer, + range); } - } else { - ret = __hv_remote_flush_tlb_with_range(kvm, - kvm_get_vcpu(kvm, 0), range); + } else if (VALID_PAGE(to_kvm_vmx(kvm)->hv_tlb_eptp)) { + ret = hv_remote_flush_eptp(to_kvm_vmx(kvm)->hv_tlb_eptp, range); } spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock); diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 5961cb897125..3d557a065c01 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -301,6 +301,7 @@ struct kvm_vmx { bool ept_identity_pagetable_done; gpa_t ept_identity_map_addr; + hpa_t hv_tlb_eptp; enum ept_pointers_status ept_pointers_match; spinlock_t ept_pointer_lock; };
Explicitly track the EPTP that is common to all vCPUs instead of grabbing vCPU0's EPTP when invoking Hyper-V's paravirt TLB flush. Tracking the EPTP will allow optimizing the checks when loading a new EPTP and will also allow dropping ept_pointer_match, e.g. by marking the common EPTP as invalid. This also technically fixes a bug where KVM could theoretically flush an invalid GPA if all vCPUs have an invalid root. In practice, it's likely impossible to trigger a remote TLB flush in such a scenario. In any case, the superfluous flush is completely benign. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/vmx/vmx.c | 19 ++++++++----------- arch/x86/kvm/vmx/vmx.h | 1 + 2 files changed, 9 insertions(+), 11 deletions(-)