KVM: SVM: Treat exit_code as an unsigned 64-bit value through all of KVM

Fix KVM's long-standing buggy handling of SVM's exit_code as a 32-bit
value.  Per the APM and Xen commit d1bd157fbc ("Big merge the HVM
full-virtualisation abstractions.") (which is arguably more trustworthy
than KVM), offset 0x70 is a single 64-bit value:

  070h 63:0 EXITCODE

Track exit_code as a single u64 to prevent reintroducing bugs where KVM
neglects to correctly set bits 63:32.

Fixes: 6aa8b73 ("[PATCH] kvm: userspace interface")
Cc: Jim Mattson <jmattson@google.com>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251230211347.4099600-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/include/asm/svm.h

@@ -137,8 +137,7 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 	u32 int_vector;
 	u32 int_state;
 	u8 reserved_3[4];
-	u32 exit_code;
-	u32 exit_code_hi;
+	u64 exit_code;
 	u64 exit_info_1;
 	u64 exit_info_2;
 	u32 exit_int_info;

arch/x86/include/uapi/asm/svm.h

@@ -103,38 +103,38 @@
 #define SVM_EXIT_VMGEXIT       0x403
 
 /* SEV-ES software-defined VMGEXIT events */
-#define SVM_VMGEXIT_MMIO_READ			0x80000001
-#define SVM_VMGEXIT_MMIO_WRITE			0x80000002
-#define SVM_VMGEXIT_NMI_COMPLETE		0x80000003
-#define SVM_VMGEXIT_AP_HLT_LOOP			0x80000004
-#define SVM_VMGEXIT_AP_JUMP_TABLE		0x80000005
+#define SVM_VMGEXIT_MMIO_READ			0x80000001ull
+#define SVM_VMGEXIT_MMIO_WRITE			0x80000002ull
+#define SVM_VMGEXIT_NMI_COMPLETE		0x80000003ull
+#define SVM_VMGEXIT_AP_HLT_LOOP			0x80000004ull
+#define SVM_VMGEXIT_AP_JUMP_TABLE		0x80000005ull
 #define SVM_VMGEXIT_SET_AP_JUMP_TABLE		0
 #define SVM_VMGEXIT_GET_AP_JUMP_TABLE		1
-#define SVM_VMGEXIT_PSC				0x80000010
-#define SVM_VMGEXIT_GUEST_REQUEST		0x80000011
-#define SVM_VMGEXIT_EXT_GUEST_REQUEST		0x80000012
-#define SVM_VMGEXIT_AP_CREATION			0x80000013
+#define SVM_VMGEXIT_PSC				0x80000010ull
+#define SVM_VMGEXIT_GUEST_REQUEST		0x80000011ull
+#define SVM_VMGEXIT_EXT_GUEST_REQUEST		0x80000012ull
+#define SVM_VMGEXIT_AP_CREATION			0x80000013ull
 #define SVM_VMGEXIT_AP_CREATE_ON_INIT		0
 #define SVM_VMGEXIT_AP_CREATE			1
 #define SVM_VMGEXIT_AP_DESTROY			2
-#define SVM_VMGEXIT_SNP_RUN_VMPL		0x80000018
-#define SVM_VMGEXIT_SAVIC			0x8000001a
+#define SVM_VMGEXIT_SNP_RUN_VMPL		0x80000018ull
+#define SVM_VMGEXIT_SAVIC			0x8000001aull
 #define SVM_VMGEXIT_SAVIC_REGISTER_GPA		0
 #define SVM_VMGEXIT_SAVIC_UNREGISTER_GPA	1
 #define SVM_VMGEXIT_SAVIC_SELF_GPA		~0ULL
-#define SVM_VMGEXIT_HV_FEATURES			0x8000fffd
-#define SVM_VMGEXIT_TERM_REQUEST		0x8000fffe
+#define SVM_VMGEXIT_HV_FEATURES			0x8000fffdull
+#define SVM_VMGEXIT_TERM_REQUEST		0x8000fffeull
 #define SVM_VMGEXIT_TERM_REASON(reason_set, reason_code)	\
 	/* SW_EXITINFO1[3:0] */					\
 	(((((u64)reason_set) & 0xf)) |				\
 	/* SW_EXITINFO1[11:4] */				\
 	((((u64)reason_code) & 0xff) << 4))
-#define SVM_VMGEXIT_UNSUPPORTED_EVENT		0x8000ffff
+#define SVM_VMGEXIT_UNSUPPORTED_EVENT		0x8000ffffull
 
 /* Exit code reserved for hypervisor/software use */
-#define SVM_EXIT_SW				0xf0000000
+#define SVM_EXIT_SW				0xf0000000ull
 
-#define SVM_EXIT_ERR           -1
+#define SVM_EXIT_ERR           -1ull
 
 #define SVM_EXIT_REASONS \
 	{ SVM_EXIT_READ_CR0,    "read_cr0" }, \

arch/x86/kvm/svm/hyperv.c

@@ -11,7 +11,6 @@ void svm_hv_inject_synthetic_vmexit_post_tlb_flush(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	svm->vmcb->control.exit_code = HV_SVM_EXITCODE_ENL;
-	svm->vmcb->control.exit_code_hi = 0;
 	svm->vmcb->control.exit_info_1 = HV_SVM_ENL_EXITCODE_TRAP_AFTER_FLUSH;
 	svm->vmcb->control.exit_info_2 = 0;
 	nested_svm_vmexit(svm);

arch/x86/kvm/svm/nested.c

@@ -45,7 +45,6 @@ static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
 		 * correctly fill in the high bits of exit_info_1.
 		 */
 		vmcb->control.exit_code = SVM_EXIT_NPF;
-		vmcb->control.exit_code_hi = 0;
 		vmcb->control.exit_info_1 = (1ULL << 32);
 		vmcb->control.exit_info_2 = fault->address;
 	}
@@ -441,7 +440,6 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu,
 	to->int_vector          = from->int_vector;
 	to->int_state           = from->int_state;
 	to->exit_code           = from->exit_code;
-	to->exit_code_hi        = from->exit_code_hi;
 	to->exit_info_1         = from->exit_info_1;
 	to->exit_info_2         = from->exit_info_2;
 	to->exit_int_info       = from->exit_int_info;
@@ -747,8 +745,8 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm,
 	enter_guest_mode(vcpu);
 
 	/*
-	 * Filled at exit: exit_code, exit_code_hi, exit_info_1, exit_info_2,
-	 * exit_int_info, exit_int_info_err, next_rip, insn_len, insn_bytes.
+	 * Filled at exit: exit_code, exit_info_1, exit_info_2, exit_int_info,
+	 * exit_int_info_err, next_rip, insn_len, insn_bytes.
 	 */
 
 	if (guest_cpu_cap_has(vcpu, X86_FEATURE_VGIF) &&
@@ -1018,7 +1016,6 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 	if (!nested_vmcb_check_save(vcpu) ||
 	    !nested_vmcb_check_controls(vcpu)) {
 		vmcb12->control.exit_code    = SVM_EXIT_ERR;
-		vmcb12->control.exit_code_hi = -1u;
 		vmcb12->control.exit_info_1  = 0;
 		vmcb12->control.exit_info_2  = 0;
 		goto out;
@@ -1051,7 +1048,6 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 	svm->soft_int_injected = false;
 
 	svm->vmcb->control.exit_code    = SVM_EXIT_ERR;
-	svm->vmcb->control.exit_code_hi = -1u;
 	svm->vmcb->control.exit_info_1  = 0;
 	svm->vmcb->control.exit_info_2  = 0;
 
@@ -1163,7 +1159,6 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
 
 	vmcb12->control.int_state         = vmcb02->control.int_state;
 	vmcb12->control.exit_code         = vmcb02->control.exit_code;
-	vmcb12->control.exit_code_hi      = vmcb02->control.exit_code_hi;
 	vmcb12->control.exit_info_1       = vmcb02->control.exit_info_1;
 	vmcb12->control.exit_info_2       = vmcb02->control.exit_info_2;
 
@@ -1460,7 +1455,7 @@ static int nested_svm_intercept_ioio(struct vcpu_svm *svm)
 
 static int nested_svm_intercept(struct vcpu_svm *svm)
 {
-	u32 exit_code = svm->vmcb->control.exit_code;
+	u64 exit_code = svm->vmcb->control.exit_code;
 	int vmexit = NESTED_EXIT_HOST;
 
 	if (svm_is_vmrun_failure(exit_code))
@@ -1532,7 +1527,6 @@ static void nested_svm_inject_exception_vmexit(struct kvm_vcpu *vcpu)
 	struct vmcb *vmcb = svm->vmcb;
 
 	vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + ex->vector;
-	vmcb->control.exit_code_hi = 0;
 
 	if (ex->has_error_code)
 		vmcb->control.exit_info_1 = ex->error_code;
@@ -1708,7 +1702,6 @@ static void nested_copy_vmcb_cache_to_control(struct vmcb_control_area *dst,
 	dst->int_vector           = from->int_vector;
 	dst->int_state            = from->int_state;
 	dst->exit_code            = from->exit_code;
-	dst->exit_code_hi         = from->exit_code_hi;
 	dst->exit_info_1          = from->exit_info_1;
 	dst->exit_info_2          = from->exit_info_2;
 	dst->exit_int_info        = from->exit_int_info;

arch/x86/kvm/svm/sev.c

@@ -3270,11 +3270,6 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
 		kvfree(svm->sev_es.ghcb_sa);
 }
 
-static u64 kvm_get_cached_sw_exit_code(struct vmcb_control_area *control)
-{
-	return (((u64)control->exit_code_hi) << 32) | control->exit_code;
-}
-
 static void dump_ghcb(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -3296,7 +3291,7 @@ static void dump_ghcb(struct vcpu_svm *svm)
 	 */
 	pr_err("GHCB (GPA=%016llx) snapshot:\n", svm->vmcb->control.ghcb_gpa);
 	pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_code",
-	       kvm_get_cached_sw_exit_code(control), kvm_ghcb_sw_exit_code_is_valid(svm));
+	       control->exit_code, kvm_ghcb_sw_exit_code_is_valid(svm));
 	pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_info_1",
 	       control->exit_info_1, kvm_ghcb_sw_exit_info_1_is_valid(svm));
 	pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_info_2",
@@ -3330,7 +3325,6 @@ static void sev_es_sync_from_ghcb(struct vcpu_svm *svm)
 	struct vmcb_control_area *control = &svm->vmcb->control;
 	struct kvm_vcpu *vcpu = &svm->vcpu;
 	struct ghcb *ghcb = svm->sev_es.ghcb;
-	u64 exit_code;
 
 	/*
 	 * The GHCB protocol so far allows for the following data
@@ -3364,9 +3358,7 @@ static void sev_es_sync_from_ghcb(struct vcpu_svm *svm)
 		__kvm_emulate_msr_write(vcpu, MSR_IA32_XSS, kvm_ghcb_get_xss(svm));
 
 	/* Copy the GHCB exit information into the VMCB fields */
-	exit_code = kvm_ghcb_get_sw_exit_code(svm);
-	control->exit_code = lower_32_bits(exit_code);
-	control->exit_code_hi = upper_32_bits(exit_code);
+	control->exit_code = kvm_ghcb_get_sw_exit_code(svm);
 	control->exit_info_1 = kvm_ghcb_get_sw_exit_info_1(svm);
 	control->exit_info_2 = kvm_ghcb_get_sw_exit_info_2(svm);
 	svm->sev_es.sw_scratch = kvm_ghcb_get_sw_scratch_if_valid(svm);
@@ -3379,15 +3371,8 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
 	struct kvm_vcpu *vcpu = &svm->vcpu;
-	u64 exit_code;
 	u64 reason;
 
-	/*
-	 * Retrieve the exit code now even though it may not be marked valid
-	 * as it could help with debugging.
-	 */
-	exit_code = kvm_get_cached_sw_exit_code(control);
-
 	/* Only GHCB Usage code 0 is supported */
 	if (svm->sev_es.ghcb->ghcb_usage) {
 		reason = GHCB_ERR_INVALID_USAGE;
@@ -3401,7 +3386,7 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	    !kvm_ghcb_sw_exit_info_2_is_valid(svm))
 		goto vmgexit_err;
 
-	switch (exit_code) {
+	switch (control->exit_code) {
 	case SVM_EXIT_READ_DR7:
 		break;
 	case SVM_EXIT_WRITE_DR7:
@@ -3502,15 +3487,19 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	return 0;
 
 vmgexit_err:
+	/*
+	 * Print the exit code even though it may not be marked valid as it
+	 * could help with debugging.
+	 */
 	if (reason == GHCB_ERR_INVALID_USAGE) {
 		vcpu_unimpl(vcpu, "vmgexit: ghcb usage %#x is not valid\n",
 			    svm->sev_es.ghcb->ghcb_usage);
 	} else if (reason == GHCB_ERR_INVALID_EVENT) {
 		vcpu_unimpl(vcpu, "vmgexit: exit code %#llx is not valid\n",
-			    exit_code);
+			    control->exit_code);
 	} else {
 		vcpu_unimpl(vcpu, "vmgexit: exit code %#llx input is not valid\n",
-			    exit_code);
+			    control->exit_code);
 		dump_ghcb(svm);
 	}
 
@@ -4349,7 +4338,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct vmcb_control_area *control = &svm->vmcb->control;
-	u64 ghcb_gpa, exit_code;
+	u64 ghcb_gpa;
 	int ret;
 
 	/* Validate the GHCB */
@@ -4391,8 +4380,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 
 	svm_vmgexit_success(svm, 0);
 
-	exit_code = kvm_get_cached_sw_exit_code(control);
-	switch (exit_code) {
+	switch (control->exit_code) {
 	case SVM_VMGEXIT_MMIO_READ:
 		ret = setup_vmgexit_scratch(svm, true, control->exit_info_2);
 		if (ret)
@@ -4484,7 +4472,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 		ret = -EINVAL;
 		break;
 	default:
-		ret = svm_invoke_exit_handler(vcpu, exit_code);
+		ret = svm_invoke_exit_handler(vcpu, control->exit_code);
 	}
 
 	return ret;

arch/x86/kvm/svm/svm.c

@@ -2466,7 +2466,6 @@ static bool check_selective_cr0_intercepted(struct kvm_vcpu *vcpu,
 
 	if (cr0 ^ val) {
 		svm->vmcb->control.exit_code = SVM_EXIT_CR0_SEL_WRITE;
-		svm->vmcb->control.exit_code_hi = 0;
 		ret = (nested_svm_exit_handled(svm) == NESTED_EXIT_DONE);
 	}
 
@@ -3299,7 +3298,7 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
 	pr_err("%-20s%08x\n", "int_ctl:", control->int_ctl);
 	pr_err("%-20s%08x\n", "int_vector:", control->int_vector);
 	pr_err("%-20s%08x\n", "int_state:", control->int_state);
-	pr_err("%-20s%08x\n", "exit_code:", control->exit_code);
+	pr_err("%-20s%016llx\n", "exit_code:", control->exit_code);
 	pr_err("%-20s%016llx\n", "exit_info1:", control->exit_info_1);
 	pr_err("%-20s%016llx\n", "exit_info2:", control->exit_info_2);
 	pr_err("%-20s%08x\n", "exit_int_info:", control->exit_int_info);
@@ -3549,7 +3548,6 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_run *kvm_run = vcpu->run;
-	u32 exit_code = svm->vmcb->control.exit_code;
 
 	/* SEV-ES guests must use the CR write traps to track CR registers. */
 	if (!sev_es_guest(vcpu->kvm)) {
@@ -3585,7 +3583,7 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	if (exit_fastpath != EXIT_FASTPATH_NONE)
 		return 1;
 
-	return svm_invoke_exit_handler(vcpu, exit_code);
+	return svm_invoke_exit_handler(vcpu, svm->vmcb->control.exit_code);
 }
 
 static int pre_svm_run(struct kvm_vcpu *vcpu)
@@ -4670,7 +4668,6 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
 	if (static_cpu_has(X86_FEATURE_NRIPS))
 		vmcb->control.next_rip  = info->next_rip;
 	vmcb->control.exit_code = icpt_info.exit_code;
-	vmcb->control.exit_code_hi = 0;
 	vmexit = nested_svm_exit_handled(svm);
 
 	ret = (vmexit == NESTED_EXIT_DONE) ? X86EMUL_INTERCEPTED

arch/x86/kvm/svm/svm.h

@@ -160,8 +160,7 @@ struct vmcb_ctrl_area_cached {
 	u32 int_ctl;
 	u32 int_vector;
 	u32 int_state;
-	u32 exit_code;
-	u32 exit_code_hi;
+	u64 exit_code;
 	u64 exit_info_1;
 	u64 exit_info_2;
 	u32 exit_int_info;
@@ -787,7 +786,6 @@ int nested_svm_vmexit(struct vcpu_svm *svm);
 static inline int nested_svm_simple_vmexit(struct vcpu_svm *svm, u32 exit_code)
 {
 	svm->vmcb->control.exit_code	= exit_code;
-	svm->vmcb->control.exit_code_hi	= 0;
 	svm->vmcb->control.exit_info_1	= 0;
 	svm->vmcb->control.exit_info_2	= 0;
 	return nested_svm_vmexit(svm);

arch/x86/kvm/trace.h

@@ -383,10 +383,10 @@ TRACE_EVENT(kvm_apic,
 #define kvm_print_exit_reason(exit_reason, isa)				\
 	(isa == KVM_ISA_VMX) ?						\
 	__print_symbolic(exit_reason & 0xffff, VMX_EXIT_REASONS) :	\
-	__print_symbolic(exit_reason, SVM_EXIT_REASONS),		\
+	__print_symbolic_u64(exit_reason, SVM_EXIT_REASONS),		\
 	(isa == KVM_ISA_VMX && exit_reason & ~0xffff) ? " " : "",	\
 	(isa == KVM_ISA_VMX) ?						\
-	__print_flags(exit_reason & ~0xffff, " ", VMX_EXIT_REASON_FLAGS) : ""
+	__print_flags_u64(exit_reason & ~0xffff, " ", VMX_EXIT_REASON_FLAGS) : ""
 
 #define TRACE_EVENT_KVM_EXIT(name)					     \
 TRACE_EVENT(name,							     \
@@ -781,7 +781,7 @@ TRACE_EVENT_KVM_EXIT(kvm_nested_vmexit);
  * Tracepoint for #VMEXIT reinjected to the guest
  */
 TRACE_EVENT(kvm_nested_vmexit_inject,
-	    TP_PROTO(__u32 exit_code,
+	    TP_PROTO(__u64 exit_code,
 		     __u64 exit_info1, __u64 exit_info2,
 		     __u32 exit_int_info, __u32 exit_int_info_err, __u32 isa),
 	    TP_ARGS(exit_code, exit_info1, exit_info2,

include/hyperv/hvgdk.h

@@ -281,7 +281,7 @@ struct hv_vmcb_enlightenments {
 #define HV_VMCB_NESTED_ENLIGHTENMENTS		31
 
 /* Synthetic VM-Exit */
-#define HV_SVM_EXITCODE_ENL			0xf0000000
+#define HV_SVM_EXITCODE_ENL			0xf0000000ull
 #define HV_SVM_ENL_EXITCODE_TRAP_AFTER_FLUSH	(1)
 
 /* VM_PARTITION_ASSIST_PAGE */

tools/testing/selftests/kvm/include/x86/svm.h

@@ -92,8 +92,7 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 	u32 int_vector;
 	u32 int_state;
 	u8 reserved_3[4];
-	u32 exit_code;
-	u32 exit_code_hi;
+	u64 exit_code;
 	u64 exit_info_1;
 	u64 exit_info_2;
 	u32 exit_int_info;