KVM: nVMX: Add helpers to identify shadowed VMCS fields

So that future optimizations related to shadowed fields don't need to
define their own switch statement.

Add a BUILD_BUG_ON() to ensure at least one of the types (RW vs RO) is
defined when including vmcs_shadow_fields.h (guess who keeps mistyping
SHADOW_FIELD_RO as SHADOW_FIELD_R0).

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

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index fc2b8f4cf45ff35105aaf84fa139f306528e9e5f..0d9a239b9df97012e1c9bc4fdbff61ea16ffafe1 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4420,6 +4420,29 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
        return nested_vmx_succeed(vcpu);
 }
 
+static bool is_shadow_field_rw(unsigned long field)
+{
+       switch (field) {
+#define SHADOW_FIELD_RW(x, y) case x:
+#include "vmcs_shadow_fields.h"
+               return true;
+       default:
+               break;
+       }
+       return false;
+}
+
+static bool is_shadow_field_ro(unsigned long field)
+{
+       switch (field) {
+#define SHADOW_FIELD_RO(x, y) case x:
+#include "vmcs_shadow_fields.h"
+               return true;
+       default:
+               break;
+       }
+       return false;
+}
 
 static int handle_vmwrite(struct kvm_vcpu *vcpu)
 {
@@ -4503,41 +4526,27 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
        vmcs12_write_any(vmcs12, field, offset, field_value);
 
        /*
-        * Do not track vmcs12 dirty-state if in guest-mode
-        * as we actually dirty shadow vmcs12 instead of vmcs12.
+        * Do not track vmcs12 dirty-state if in guest-mode as we actually
+        * dirty shadow vmcs12 instead of vmcs12.  Fields that can be updated
+        * by L1 without a vmexit are always updated in the vmcs02, i.e. don't
+        * "dirty" vmcs12, all others go down the prepare_vmcs02() slow path.
         */
-       if (!is_guest_mode(vcpu)) {
-               switch (field) {
-#define SHADOW_FIELD_RW(x, y) case x:
-#include "vmcs_shadow_fields.h"
-                       /*
-                        * The fields that can be updated by L1 without a vmexit are
-                        * always updated in the vmcs02, the others go down the slow
-                        * path of prepare_vmcs02.
-                        */
-                       break;
-
-#define SHADOW_FIELD_RO(x, y) case x:
-#include "vmcs_shadow_fields.h"
-                       /*
-                        * L1 can read these fields without exiting, ensure the
-                        * shadow VMCS is up-to-date.
-                        */
-                       if (enable_shadow_vmcs) {
-                               preempt_disable();
-                               vmcs_load(vmx->vmcs01.shadow_vmcs);
+       if (!is_guest_mode(vcpu) && !is_shadow_field_rw(field)) {
+               /*
+                * L1 can read these fields without exiting, ensure the
+                * shadow VMCS is up-to-date.
+                */
+               if (enable_shadow_vmcs && is_shadow_field_ro(field)) {
+                       preempt_disable();
+                       vmcs_load(vmx->vmcs01.shadow_vmcs);
 
-                               __vmcs_writel(field, field_value);
+                       __vmcs_writel(field, field_value);
 
-                               vmcs_clear(vmx->vmcs01.shadow_vmcs);
-                               vmcs_load(vmx->loaded_vmcs->vmcs);
-                               preempt_enable();
-                       }
-                       /* fall through */
-               default:
-                       vmx->nested.dirty_vmcs12 = true;
-                       break;
+                       vmcs_clear(vmx->vmcs01.shadow_vmcs);
+                       vmcs_load(vmx->loaded_vmcs->vmcs);
+                       preempt_enable();
                }
+               vmx->nested.dirty_vmcs12 = true;
        }
 
        return nested_vmx_succeed(vcpu);

diff --git a/arch/x86/kvm/vmx/vmcs_shadow_fields.h b/arch/x86/kvm/vmx/vmcs_shadow_fields.h
index 2cfa19ca158e24812d0b08e13a098bfd72af9659..4cea018ba285bc84aef3633adbe5c3750a21ba9f 100644 (file)
--- a/arch/x86/kvm/vmx/vmcs_shadow_fields.h
+++ b/arch/x86/kvm/vmx/vmcs_shadow_fields.h
@@ -1,3 +1,7 @@
+#if !defined(SHADOW_FIELD_RO) && !defined(SHADOW_FIELD_RW)
+BUILD_BUG_ON(1)
+#endif
+
 #ifndef SHADOW_FIELD_RO
 #define SHADOW_FIELD_RO(x, y)
 #endif