KVM: nVMX: Use a gfn_to_hva_cache for vmptrld

And thus another call to kvm_vcpu_map() can die.
Signed-off-by: NDavid Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20211115165030.7422-7-dwmw2@infradead.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -5286,10 +5286,11 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 		return 1;
 
 	if (vmx->nested.current_vmptr != vmptr) {
-		struct kvm_host_map map;
-		struct vmcs12 *new_vmcs12;
+		struct gfn_to_hva_cache *ghc = &vmx->nested.vmcs12_cache;
+		struct vmcs_hdr hdr;
 
-		if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmptr), &map)) {
+		if (ghc->gpa != vmptr &&
+		    kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, vmptr, VMCS12_SIZE)) {
 			/*
 			 * Reads from an unbacked page return all 1s,
 			 * which means that the 32 bits located at the
@@ -5300,12 +5301,16 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 				VMXERR_VMPTRLD_INCORRECT_VMCS_REVISION_ID);
 		}
 
-		new_vmcs12 = map.hva;
+		if (kvm_read_guest_offset_cached(vcpu->kvm, ghc, &hdr,
+						 offsetof(struct vmcs12, hdr),
+						 sizeof(hdr))) {
+			return nested_vmx_fail(vcpu,
+				VMXERR_VMPTRLD_INCORRECT_VMCS_REVISION_ID);
+		}
 
-		if (new_vmcs12->hdr.revision_id != VMCS12_REVISION ||
-		    (new_vmcs12->hdr.shadow_vmcs &&
+		if (hdr.revision_id != VMCS12_REVISION ||
+		    (hdr.shadow_vmcs &&
 		     !nested_cpu_has_vmx_shadow_vmcs(vcpu))) {
-			kvm_vcpu_unmap(vcpu, &map, false);
 			return nested_vmx_fail(vcpu,
 				VMXERR_VMPTRLD_INCORRECT_VMCS_REVISION_ID);
 		}
@@ -5316,8 +5321,11 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 		 * Load VMCS12 from guest memory since it is not already
 		 * cached.
 		 */
-		memcpy(vmx->nested.cached_vmcs12, new_vmcs12, VMCS12_SIZE);
-		kvm_vcpu_unmap(vcpu, &map, false);
+		if (kvm_read_guest_cached(vcpu->kvm, ghc, vmx->nested.cached_vmcs12,
+					  VMCS12_SIZE)) {
+			return nested_vmx_fail(vcpu,
+				VMXERR_VMPTRLD_INCORRECT_VMCS_REVISION_ID);
+		}
 
 		set_current_vmptr(vmx, vmptr);
 	}

arch/x86/kvm/vmx/vmx.h

@@ -146,6 +146,11 @@ struct nested_vmx {
 	 */
 	struct gfn_to_hva_cache shadow_vmcs12_cache;
 
+	/*
+	 * GPA to HVA cache for VMCS12
+	 */
+	struct gfn_to_hva_cache vmcs12_cache;
+
 	/*
 	 * Indicates if the shadow vmcs or enlightened vmcs must be updated
 	 * with the data held by struct vmcs12.