KVM: x86: Modify struct kvm_nested_state to have explicit fields for data

Improve the KVM_{GET,SET}_NESTED_STATE structs by detailing the format
of VMX nested state data in a struct.

In order to avoid changing the ioctl values of
KVM_{GET,SET}_NESTED_STATE, there is a need to preserve
sizeof(struct kvm_nested_state). This is done by defining the data
struct as "data.vmx[0]". It was the most elegant way I found to
preserve struct size while still keeping struct readable and easy to
maintain. It does have a misfortunate side-effect that now it has to be
accessed as "data.vmx[0]" rather than just "data.vmx".

Because we are already modifying these structs, I also modified the
following:
* Define the "format" field values as macros.
* Rename vmcs_pa to vmcs12_pa for better readability.

Signed-off-by: Liran Alon <liran.alon@oracle.com>
[Remove SVM stubs, add KVM_STATE_NESTED_VMX_VMCS12_SIZE. - Paolo]
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 22 insertions, 11 deletions

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 7a0e64ccd6ff..d6ab5b4d15e5 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -383,6 +383,9 @@ struct kvm_sync_regs {
 #define KVM_X86_QUIRK_LAPIC_MMIO_HOLE	(1 << 2)
 #define KVM_X86_QUIRK_OUT_7E_INC_RIP	(1 << 3)
 
+#define KVM_STATE_NESTED_FORMAT_VMX	0
+#define KVM_STATE_NESTED_FORMAT_SVM	1	/* unused */
+
 #define KVM_STATE_NESTED_GUEST_MODE	0x00000001
 #define KVM_STATE_NESTED_RUN_PENDING	0x00000002
 #define KVM_STATE_NESTED_EVMCS		0x00000004
@@ -390,9 +393,16 @@ struct kvm_sync_regs {
 #define KVM_STATE_NESTED_SMM_GUEST_MODE	0x00000001
 #define KVM_STATE_NESTED_SMM_VMXON	0x00000002
 
-struct kvm_vmx_nested_state {
+#define KVM_STATE_NESTED_VMX_VMCS_SIZE	0x1000
+
+struct kvm_vmx_nested_state_data {
+	__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+	__u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+};
+
+struct kvm_vmx_nested_state_hdr {
 	__u64 vmxon_pa;
-	__u64 vmcs_pa;
+	__u64 vmcs12_pa;
 
 	struct {
 		__u16 flags;
@@ -401,24 +411,25 @@ struct kvm_vmx_nested_state {
 
 /* for KVM_CAP_NESTED_STATE */
 struct kvm_nested_state {
-	/* KVM_STATE_* flags */
 	__u16 flags;
-
-	/* 0 for VMX, 1 for SVM.  */
 	__u16 format;
-
-	/* 128 for SVM, 128 + VMCS size for VMX.  */
 	__u32 size;
 
 	union {
-		/* VMXON, VMCS */
-		struct kvm_vmx_nested_state vmx;
+		struct kvm_vmx_nested_state_hdr vmx;
 
 		/* Pad the header to 128 bytes.  */
 		__u8 pad[120];
-	};
+	} hdr;
 
-	__u8 data[0];
+	/*
+	 * Define data region as 0 bytes to preserve backwards-compatability
+	 * to old definition of kvm_nested_state in order to avoid changing
+	 * KVM_{GET,PUT}_NESTED_STATE ioctl values.
+	 */
+	union {
+		struct kvm_vmx_nested_state_data vmx[0];
+	} data;
 };
 
 #endif /* _ASM_X86_KVM_H */