KVM: SVM: Flush Hyper-V TLB when required

The Hyper-V "EnlightenedNptTlb" enlightenment is always enabled when KVM
is running on top of Hyper-V and Hyper-V exposes support for it (which
is always). On AMD CPUs this enlightenment results in ASID invalidations
not flushing TLB entries derived from the NPT. To force the underlying
(L0) hypervisor to rebuild its shadow page tables, an explicit hypercall
is needed.

The original KVM implementation of Hyper-V's "EnlightenedNptTlb" on SVM
only added remote TLB flush hooks. This worked out fine for a while, as
sufficient remote TLB flushes where being issued in KVM to mask the
problem. Since v5.17, changes in the TDP code reduced the number of
flushes and the out-of-sync TLB prevents guests from booting
successfully.

Split svm_flush_tlb_current() into separate callbacks for the 3 cases
(guest/all/current), and issue the required Hyper-V hypercall when a
Hyper-V TLB flush is needed. The most important case where the TLB flush
was missing is when loading a new PGD, which is followed by what is now
svm_flush_tlb_current().

Cc: stable@vger.kernel.org # v5.17+
Fixes: 1e0c7d40758b ("KVM: SVM: hyper-v: Remote TLB flush for SVM")
Link: https://lore.kernel.org/lkml/43980946-7bbf-dcef-7e40-af904c456250@linux.microsoft.com/
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20230324145233.4585-1-jpiotrowski@linux.microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
index cff838f15db5..786d46d73a8e 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;
+}
+
 static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
 {
 	struct hv_vmcb_enlightenments *hve = &vmcb->control.hv_enlightenments;
@@ -80,6 +90,11 @@ static inline void svm_hv_update_vp_id(struct vmcb *vmcb, struct kvm_vcpu *vcpu)
 }
 #else
 
+static inline bool svm_hv_is_enlightened_tlb_enabled(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
 {
 }