KVM: nSVM: fix few bugs in the vmcb02 caching logic

* Define and use an invalid GPA (all ones) for init value of last
  and current nested vmcb physical addresses.

* Reset the current vmcb12 gpa to the invalid value when leaving
  the nested mode, similar to what is done on nested vmexit.

* Reset	the last seen vmcb12 address when disabling the nested SVM,
  as it relies on vmcb02 fields which are freed at that point.

Fixes: 4995a3685f1b ("KVM: SVM: Use a separate vmcb for the nested L2 guest")

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210503125446.1353307-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index cbbcee0..848956b 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -113,6 +113,7 @@
 #define VALID_PAGE(x) ((x) != INVALID_PAGE)
 
 #define UNMAPPED_GVA (~(gpa_t)0)
+#define INVALID_GPA (~(gpa_t)0)
 
 /* KVM Hugepage definitions for x86 */
 #define KVM_MAX_HUGEPAGE_LEVEL PG_LEVEL_1G

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 3321220..a88c64e 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -872,6 +872,15 @@ void svm_free_nested(struct vcpu_svm *svm)
        __free_page(virt_to_page(svm->nested.vmcb02.ptr));
        svm->nested.vmcb02.ptr = NULL;
 
+       /*
+        * When last_vmcb12_gpa matches the current vmcb12 gpa,
+        * some vmcb12 fields are not loaded if they are marked clean
+        * in the vmcb12, since in this case they are up to date already.
+        *
+        * When the vmcb02 is freed, this optimization becomes invalid.
+        */
+       svm->nested.last_vmcb12_gpa = INVALID_GPA;
+
        svm->nested.initialized = false;
 }
 
@@ -884,6 +893,8 @@ void svm_leave_nested(struct vcpu_svm *svm)
 
        if (is_guest_mode(vcpu)) {
                svm->nested.nested_run_pending = 0;
+               svm->nested.vmcb12_gpa = INVALID_GPA;
+
                leave_guest_mode(vcpu);
 
                svm_switch_vmcb(svm, &svm->vmcb01);

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9790c73..be5cf61 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1235,8 +1235,8 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
        svm->current_vmcb->asid_generation = 0;
        svm->asid = 0;
 
-       svm->nested.vmcb12_gpa = 0;
-       svm->nested.last_vmcb12_gpa = 0;
+       svm->nested.vmcb12_gpa = INVALID_GPA;
+       svm->nested.last_vmcb12_gpa = INVALID_GPA;
        vcpu->arch.hflags = 0;
 
        if (!kvm_pause_in_guest(vcpu->kvm)) {