KVM: SVM: Name and check reserved fields with structs offset

Rename reserved fields on all structs in arch/x86/include/asm/svm.h
following their offset within the structs. Include compile time checks for
this in the same place where other BUILD_BUG_ON for the structs are.

This also solves that fields of struct sev_es_save_area are named by their
order of appearance, but right now they jump from reserved_5 to reserved_7.

Link: https://lkml.org/lkml/2022/10/22/376Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Message-Id: <20221024164448.203351-1-carlos.bilbao@amd.com>
[Use ASSERT_STRUCT_OFFSET + fix a couple wrong offsets. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/svm.h

@@ -293,12 +293,13 @@ struct vmcb_save_area {
 	struct vmcb_seg ldtr;
 	struct vmcb_seg idtr;
 	struct vmcb_seg tr;
-	u8 reserved_1[42];
+	/* Reserved fields are named following their struct offset */
+	u8 reserved_0xa0[42];
 	u8 vmpl;
 	u8 cpl;
-	u8 reserved_2[4];
+	u8 reserved_0xcc[4];
 	u64 efer;
-	u8 reserved_3[112];
+	u8 reserved_0xd8[112];
 	u64 cr4;
 	u64 cr3;
 	u64 cr0;
@@ -306,7 +307,7 @@ struct vmcb_save_area {
 	u64 dr6;
 	u64 rflags;
 	u64 rip;
-	u8 reserved_4[88];
+	u8 reserved_0x180[88];
 	u64 rsp;
 	u64 s_cet;
 	u64 ssp;
@@ -321,14 +322,14 @@ struct vmcb_save_area {
 	u64 sysenter_esp;
 	u64 sysenter_eip;
 	u64 cr2;
-	u8 reserved_5[32];
+	u8 reserved_0x248[32];
 	u64 g_pat;
 	u64 dbgctl;
 	u64 br_from;
 	u64 br_to;
 	u64 last_excp_from;
 	u64 last_excp_to;
-	u8 reserved_6[72];
+	u8 reserved_0x298[72];
 	u32 spec_ctrl;		/* Guest version of SPEC_CTRL at 0x2E0 */
 } __packed;
 
@@ -349,12 +350,12 @@ struct sev_es_save_area {
 	u64 vmpl2_ssp;
 	u64 vmpl3_ssp;
 	u64 u_cet;
-	u8 reserved_1[2];
+	u8 reserved_0xc8[2];
 	u8 vmpl;
 	u8 cpl;
-	u8 reserved_2[4];
+	u8 reserved_0xcc[4];
 	u64 efer;
-	u8 reserved_3[104];
+	u8 reserved_0xd8[104];
 	u64 xss;
 	u64 cr4;
 	u64 cr3;
@@ -371,7 +372,7 @@ struct sev_es_save_area {
 	u64 dr1_addr_mask;
 	u64 dr2_addr_mask;
 	u64 dr3_addr_mask;
-	u8 reserved_4[24];
+	u8 reserved_0x1c0[24];
 	u64 rsp;
 	u64 s_cet;
 	u64 ssp;
@@ -386,21 +387,21 @@ struct sev_es_save_area {
 	u64 sysenter_esp;
 	u64 sysenter_eip;
 	u64 cr2;
-	u8 reserved_5[32];
+	u8 reserved_0x248[32];
 	u64 g_pat;
 	u64 dbgctl;
 	u64 br_from;
 	u64 br_to;
 	u64 last_excp_from;
 	u64 last_excp_to;
-	u8 reserved_7[80];
+	u8 reserved_0x298[80];
 	u32 pkru;
-	u8 reserved_8[20];
-	u64 reserved_9;		/* rax already available at 0x01f8 */
+	u32 tsc_aux;
+	u8 reserved_0x2f0[24];
 	u64 rcx;
 	u64 rdx;
 	u64 rbx;
-	u64 reserved_10;	/* rsp already available at 0x01d8 */
+	u64 reserved_0x320;	/* rsp already available at 0x01d8 */
 	u64 rbp;
 	u64 rsi;
 	u64 rdi;
@@ -412,7 +413,7 @@ struct sev_es_save_area {
 	u64 r13;
 	u64 r14;
 	u64 r15;
-	u8 reserved_11[16];
+	u8 reserved_0x380[16];
 	u64 guest_exit_info_1;
 	u64 guest_exit_info_2;
 	u64 guest_exit_int_info;
@@ -425,7 +426,7 @@ struct sev_es_save_area {
 	u64 pcpu_id;
 	u64 event_inj;
 	u64 xcr0;
-	u8 reserved_12[16];
+	u8 reserved_0x3f0[16];
 
 	/* Floating point area */
 	u64 x87_dp;
@@ -443,23 +444,23 @@ struct sev_es_save_area {
 } __packed;
 
 struct ghcb_save_area {
-	u8 reserved_1[203];
+	u8 reserved_0x0[203];
 	u8 cpl;
-	u8 reserved_2[116];
+	u8 reserved_0xcc[116];
 	u64 xss;
-	u8 reserved_3[24];
+	u8 reserved_0x148[24];
 	u64 dr7;
-	u8 reserved_4[16];
+	u8 reserved_0x168[16];
 	u64 rip;
-	u8 reserved_5[88];
+	u8 reserved_0x180[88];
 	u64 rsp;
-	u8 reserved_6[24];
+	u8 reserved_0x1e0[24];
 	u64 rax;
-	u8 reserved_7[264];
+	u8 reserved_0x200[264];
 	u64 rcx;
 	u64 rdx;
 	u64 rbx;
-	u8 reserved_8[8];
+	u8 reserved_0x320[8];
 	u64 rbp;
 	u64 rsi;
 	u64 rdi;
@@ -471,12 +472,12 @@ struct ghcb_save_area {
 	u64 r13;
 	u64 r14;
 	u64 r15;
-	u8 reserved_9[16];
+	u8 reserved_0x380[16];
 	u64 sw_exit_code;
 	u64 sw_exit_info_1;
 	u64 sw_exit_info_2;
 	u64 sw_scratch;
-	u8 reserved_10[56];
+	u8 reserved_0x3b0[56];
 	u64 xcr0;
 	u8 valid_bitmap[16];
 	u64 x87_state_gpa;
@@ -490,7 +491,7 @@ struct ghcb {
 
 	u8 shared_buffer[GHCB_SHARED_BUF_SIZE];
 
-	u8 reserved_1[10];
+	u8 reserved_0xff0[10];
 	u16 protocol_version;	/* negotiated SEV-ES/GHCB protocol version */
 	u32 ghcb_usage;
 } __packed;
@@ -502,6 +503,9 @@ struct ghcb {
 #define EXPECTED_VMCB_CONTROL_AREA_SIZE		1024
 #define EXPECTED_GHCB_SIZE			PAGE_SIZE
 
+#define BUILD_BUG_RESERVED_OFFSET(x, y) \
+	ASSERT_STRUCT_OFFSET(struct x, reserved ## _ ## y, y)
+
 static inline void __unused_size_checks(void)
 {
 	BUILD_BUG_ON(sizeof(struct vmcb_save_area)	!= EXPECTED_VMCB_SAVE_AREA_SIZE);
@@ -509,6 +513,39 @@ static inline void __unused_size_checks(void)
 	BUILD_BUG_ON(sizeof(struct sev_es_save_area)	!= EXPECTED_SEV_ES_SAVE_AREA_SIZE);
 	BUILD_BUG_ON(sizeof(struct vmcb_control_area)	!= EXPECTED_VMCB_CONTROL_AREA_SIZE);
 	BUILD_BUG_ON(sizeof(struct ghcb)		!= EXPECTED_GHCB_SIZE);
+
+	/* Check offsets of reserved fields */
+
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0xa0);
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0xcc);
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0xd8);
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x180);
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x248);
+	BUILD_BUG_RESERVED_OFFSET(vmcb_save_area, 0x298);
+
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0xc8);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0xcc);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0xd8);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x1c0);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x248);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x298);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x2f0);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x320);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x380);
+	BUILD_BUG_RESERVED_OFFSET(sev_es_save_area, 0x3f0);
+
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x0);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0xcc);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x148);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x168);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x180);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x1e0);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x200);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x320);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x380);
+	BUILD_BUG_RESERVED_OFFSET(ghcb_save_area, 0x3b0);
+
+	BUILD_BUG_RESERVED_OFFSET(ghcb, 0xff0);
 }
 
 struct vmcb {

arch/x86/kvm/svm/sev.c

@@ -2648,7 +2648,7 @@ static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
 		ghcb_scratch_beg = control->ghcb_gpa +
 				   offsetof(struct ghcb, shared_buffer);
 		ghcb_scratch_end = control->ghcb_gpa +
-				   offsetof(struct ghcb, reserved_1);
+				   offsetof(struct ghcb, reserved_0xff0);
 
 		/*
 		 * If the scratch area begins within the GHCB, it must be