KVM: nVMX: WARN if PML emulation helper is invoked outside of nested guest

WARN if vmx_write_pml_buffer() is called outside of guest mode instead
of silently ignoring the condition.  The only caller is nested EPT's
ept_update_accessed_dirty_bits(), which should only be reachable when
L2 is active.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200622215832.22090-4-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 13745f2..2c95948 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7485,32 +7485,33 @@ static int vmx_write_pml_buffer(struct kvm_vcpu *vcpu, gpa_t gpa)
        struct vcpu_vmx *vmx = to_vmx(vcpu);
        gpa_t dst;
 
-       if (is_guest_mode(vcpu)) {
-               WARN_ON_ONCE(vmx->nested.pml_full);
+       if (WARN_ON_ONCE(!is_guest_mode(vcpu)))
+               return 0;
 
-               /*
-                * Check if PML is enabled for the nested guest.
-                * Whether eptp bit 6 is set is already checked
-                * as part of A/D emulation.
-                */
-               vmcs12 = get_vmcs12(vcpu);
-               if (!nested_cpu_has_pml(vmcs12))
-                       return 0;
+       if (WARN_ON_ONCE(vmx->nested.pml_full))
+               return 1;
 
-               if (vmcs12->guest_pml_index >= PML_ENTITY_NUM) {
-                       vmx->nested.pml_full = true;
-                       return 1;
-               }
+       /*
+        * Check if PML is enabled for the nested guest. Whether eptp bit 6 is
+        * set is already checked as part of A/D emulation.
+        */
+       vmcs12 = get_vmcs12(vcpu);
+       if (!nested_cpu_has_pml(vmcs12))
+               return 0;
+
+       if (vmcs12->guest_pml_index >= PML_ENTITY_NUM) {
+               vmx->nested.pml_full = true;
+               return 1;
+       }
 
-               gpa &= ~0xFFFull;
-               dst = vmcs12->pml_address + sizeof(u64) * vmcs12->guest_pml_index;
+       gpa &= ~0xFFFull;
+       dst = vmcs12->pml_address + sizeof(u64) * vmcs12->guest_pml_index;
 
-               if (kvm_write_guest_page(vcpu->kvm, gpa_to_gfn(dst), &gpa,
-                                        offset_in_page(dst), sizeof(gpa)))
-                       return 0;
+       if (kvm_write_guest_page(vcpu->kvm, gpa_to_gfn(dst), &gpa,
+                                offset_in_page(dst), sizeof(gpa)))
+               return 0;
 
-               vmcs12->guest_pml_index--;
-       }
+       vmcs12->guest_pml_index--;
 
        return 0;
 }