Merge tag 'kvm-x86-misc-6.12' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.12

 - Advertise AVX10.1 to userspace (effectively prep work for the "real" AVX10
   functionality that is on the horizon).

 - Rework common MSR handling code to suppress errors on userspace accesses to
   unsupported-but-advertised MSRs.  This will allow removing (almost?) all of
   KVM's exemptions for userspace access to MSRs that shouldn't exist based on
   the vCPU model (the actual cleanup is non-trivial future work).

 - Rework KVM's handling of x2APIC ICR, again, because AMD (x2AVIC) splits the
   64-bit value into the legacy ICR and ICR2 storage, whereas Intel (APICv)
   stores the entire 64-bit value a the ICR offset.

 - Fix a bug where KVM would fail to exit to userspace if one was triggered by
   a fastpath exit handler.

 - Add fastpath handling of HLT VM-Exit to expedite re-entering the guest when
   there's already a pending wake event at the time of the exit.

 - Finally fix the RSM vs. nested VM-Enter WARN by forcing the vCPU out of
   guest mode prior to signalling SHUTDOWN (architecturally, the SHUTDOWN is
   supposed to hit L1, not L2).

arch/x86/include/asm/cpuid.h

@@ -179,6 +179,7 @@ static __always_inline bool cpuid_function_is_indexed(u32 function)
 	case 0x1d:
 	case 0x1e:
 	case 0x1f:
+	case 0x24:
 	case 0x8000001d:
 		return true;
 	}

arch/x86/include/asm/kvm-x86-ops.h

@@ -125,7 +125,7 @@ KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
 KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from)
 KVM_X86_OP_OPTIONAL(vm_move_enc_context_from)
 KVM_X86_OP_OPTIONAL(guest_memory_reclaimed)
-KVM_X86_OP(get_msr_feature)
+KVM_X86_OP(get_feature_msr)
 KVM_X86_OP(check_emulate_instruction)
 KVM_X86_OP(apic_init_signal_blocked)
 KVM_X86_OP_OPTIONAL(enable_l2_tlb_flush)

arch/x86/include/asm/kvm_host.h

@@ -212,6 +212,7 @@ enum exit_fastpath_completion {
 	EXIT_FASTPATH_NONE,
 	EXIT_FASTPATH_REENTER_GUEST,
 	EXIT_FASTPATH_EXIT_HANDLED,
+	EXIT_FASTPATH_EXIT_USERSPACE,
 };
 typedef enum exit_fastpath_completion fastpath_t;
 
@@ -1730,6 +1731,8 @@ struct kvm_x86_ops {
 	void (*enable_nmi_window)(struct kvm_vcpu *vcpu);
 	void (*enable_irq_window)(struct kvm_vcpu *vcpu);
 	void (*update_cr8_intercept)(struct kvm_vcpu *vcpu, int tpr, int irr);
+
+	const bool x2apic_icr_is_split;
 	const unsigned long required_apicv_inhibits;
 	bool allow_apicv_in_x2apic_without_x2apic_virtualization;
 	void (*refresh_apicv_exec_ctrl)(struct kvm_vcpu *vcpu);
@@ -1809,7 +1812,7 @@ struct kvm_x86_ops {
 	int (*vm_move_enc_context_from)(struct kvm *kvm, unsigned int source_fd);
 	void (*guest_memory_reclaimed)(struct kvm *kvm);
 
-	int (*get_msr_feature)(struct kvm_msr_entry *entry);
+	int (*get_feature_msr)(u32 msr, u64 *data);
 
 	int (*check_emulate_instruction)(struct kvm_vcpu *vcpu, int emul_type,
 					 void *insn, int insn_len);

arch/x86/kvm/cpuid.c

@@ -705,7 +705,7 @@ void kvm_set_cpu_caps(void)
 
 	kvm_cpu_cap_init_kvm_defined(CPUID_7_1_EDX,
 		F(AVX_VNNI_INT8) | F(AVX_NE_CONVERT) | F(PREFETCHITI) |
-		F(AMX_COMPLEX)
+		F(AMX_COMPLEX) | F(AVX10)
 	);
 
 	kvm_cpu_cap_init_kvm_defined(CPUID_7_2_EDX,
@@ -721,6 +721,10 @@ void kvm_set_cpu_caps(void)
 		SF(SGX1) | SF(SGX2) | SF(SGX_EDECCSSA)
 	);
 
+	kvm_cpu_cap_init_kvm_defined(CPUID_24_0_EBX,
+		F(AVX10_128) | F(AVX10_256) | F(AVX10_512)
+	);
+
 	kvm_cpu_cap_mask(CPUID_8000_0001_ECX,
 		F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ |
 		F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) |
@@ -949,7 +953,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 	switch (function) {
 	case 0:
 		/* Limited to the highest leaf implemented in KVM. */
-		entry->eax = min(entry->eax, 0x1fU);
+		entry->eax = min(entry->eax, 0x24U);
 		break;
 	case 1:
 		cpuid_entry_override(entry, CPUID_1_EDX);
@@ -1174,6 +1178,28 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 			break;
 		}
 		break;
+	case 0x24: {
+		u8 avx10_version;
+
+		if (!kvm_cpu_cap_has(X86_FEATURE_AVX10)) {
+			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+			break;
+		}
+
+		/*
+		 * The AVX10 version is encoded in EBX[7:0].  Note, the version
+		 * is guaranteed to be >=1 if AVX10 is supported.  Note #2, the
+		 * version needs to be captured before overriding EBX features!
+		 */
+		avx10_version = min_t(u8, entry->ebx & 0xff, 1);
+		cpuid_entry_override(entry, CPUID_24_0_EBX);
+		entry->ebx |= avx10_version;
+
+		entry->eax = 0;
+		entry->ecx = 0;
+		entry->edx = 0;
+		break;
+	}
 	case KVM_CPUID_SIGNATURE: {
 		const u32 *sigptr = (const u32 *)KVM_SIGNATURE;
 		entry->eax = KVM_CPUID_FEATURES;

arch/x86/kvm/lapic.c

@@ -1944,7 +1944,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
 	u64 ns = 0;
 	ktime_t expire;
 	struct kvm_vcpu *vcpu = apic->vcpu;
-	unsigned long this_tsc_khz = vcpu->arch.virtual_tsc_khz;
+	u32 this_tsc_khz = vcpu->arch.virtual_tsc_khz;
 	unsigned long flags;
 	ktime_t now;
 
@@ -2453,6 +2453,43 @@ void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi);
 
+#define X2APIC_ICR_RESERVED_BITS (GENMASK_ULL(31, 20) | GENMASK_ULL(17, 16) | BIT(13))
+
+int kvm_x2apic_icr_write(struct kvm_lapic *apic, u64 data)
+{
+	if (data & X2APIC_ICR_RESERVED_BITS)
+		return 1;
+
+	/*
+	 * The BUSY bit is reserved on both Intel and AMD in x2APIC mode, but
+	 * only AMD requires it to be zero, Intel essentially just ignores the
+	 * bit.  And if IPI virtualization (Intel) or x2AVIC (AMD) is enabled,
+	 * the CPU performs the reserved bits checks, i.e. the underlying CPU
+	 * behavior will "win".  Arbitrarily clear the BUSY bit, as there is no
+	 * sane way to provide consistent behavior with respect to hardware.
+	 */
+	data &= ~APIC_ICR_BUSY;
+
+	kvm_apic_send_ipi(apic, (u32)data, (u32)(data >> 32));
+	if (kvm_x86_ops.x2apic_icr_is_split) {
+		kvm_lapic_set_reg(apic, APIC_ICR, data);
+		kvm_lapic_set_reg(apic, APIC_ICR2, data >> 32);
+	} else {
+		kvm_lapic_set_reg64(apic, APIC_ICR, data);
+	}
+	trace_kvm_apic_write(APIC_ICR, data);
+	return 0;
+}
+
+static u64 kvm_x2apic_icr_read(struct kvm_lapic *apic)
+{
+	if (kvm_x86_ops.x2apic_icr_is_split)
+		return (u64)kvm_lapic_get_reg(apic, APIC_ICR) |
+		       (u64)kvm_lapic_get_reg(apic, APIC_ICR2) << 32;
+
+	return kvm_lapic_get_reg64(apic, APIC_ICR);
+}
+
 /* emulate APIC access in a trap manner */
 void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset)
 {
@@ -2470,7 +2507,7 @@ void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset)
 	 * maybe-unecessary write, and both are in the noise anyways.
 	 */
 	if (apic_x2apic_mode(apic) && offset == APIC_ICR)
-		kvm_x2apic_icr_write(apic, kvm_lapic_get_reg64(apic, APIC_ICR));
+		WARN_ON_ONCE(kvm_x2apic_icr_write(apic, kvm_x2apic_icr_read(apic)));
 	else
 		kvm_lapic_reg_write(apic, offset, kvm_lapic_get_reg(apic, offset));
 }
@@ -2990,12 +3027,15 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
 
 		/*
 		 * In x2APIC mode, the LDR is fixed and based on the id.  And
-		 * ICR is internally a single 64-bit register, but needs to be
-		 * split to ICR+ICR2 in userspace for backwards compatibility.
+		 * if the ICR is _not_ split, ICR is internally a single 64-bit
+		 * register, but needs to be split to ICR+ICR2 in userspace for
+		 * backwards compatibility.
 		 */
-		if (set) {
+		if (set)
 			*ldr = kvm_apic_calc_x2apic_ldr(x2apic_id);
 
+		if (!kvm_x86_ops.x2apic_icr_is_split) {
+			if (set) {
 				icr = __kvm_lapic_get_reg(s->regs, APIC_ICR) |
 				      (u64)__kvm_lapic_get_reg(s->regs, APIC_ICR2) << 32;
 				__kvm_lapic_set_reg64(s->regs, APIC_ICR, icr);
@@ -3004,6 +3044,7 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
 				__kvm_lapic_set_reg(s->regs, APIC_ICR2, icr >> 32);
 			}
 		}
+	}
 
 	return 0;
 }
@@ -3194,22 +3235,12 @@ int kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr)
 	return 0;
 }
 
-int kvm_x2apic_icr_write(struct kvm_lapic *apic, u64 data)
-{
-	data &= ~APIC_ICR_BUSY;
-
-	kvm_apic_send_ipi(apic, (u32)data, (u32)(data >> 32));
-	kvm_lapic_set_reg64(apic, APIC_ICR, data);
-	trace_kvm_apic_write(APIC_ICR, data);
-	return 0;
-}
-
 static int kvm_lapic_msr_read(struct kvm_lapic *apic, u32 reg, u64 *data)
 {
 	u32 low;
 
 	if (reg == APIC_ICR) {
-		*data = kvm_lapic_get_reg64(apic, APIC_ICR);
+		*data = kvm_x2apic_icr_read(apic);
 		return 0;
 	}
 

arch/x86/kvm/lapic.h

@@ -96,7 +96,6 @@ u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu);
 void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8);
 void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu);
 void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value);
-u64 kvm_lapic_get_base(struct kvm_vcpu *vcpu);
 void kvm_recalculate_apic_map(struct kvm *kvm);
 void kvm_apic_set_version(struct kvm_vcpu *vcpu);
 void kvm_apic_after_set_mcg_cap(struct kvm_vcpu *vcpu);

arch/x86/kvm/mmu.h

@@ -223,8 +223,6 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 
 bool kvm_mmu_may_ignore_guest_pat(void);
 
-int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
-
 int kvm_mmu_post_init_vm(struct kvm *kvm);
 void kvm_mmu_pre_destroy_vm(struct kvm *kvm);
 

arch/x86/kvm/mmu/mmu_internal.h

@@ -349,8 +349,6 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm,
 void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);
 void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_level);
 
-void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
-
 void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
 void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
 

arch/x86/kvm/reverse_cpuid.h

@@ -17,6 +17,7 @@ enum kvm_only_cpuid_leafs {
 	CPUID_8000_0007_EDX,
 	CPUID_8000_0022_EAX,
 	CPUID_7_2_EDX,
+	CPUID_24_0_EBX,
 	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
@@ -46,6 +47,7 @@ enum kvm_only_cpuid_leafs {
 #define X86_FEATURE_AVX_NE_CONVERT      KVM_X86_FEATURE(CPUID_7_1_EDX, 5)
 #define X86_FEATURE_AMX_COMPLEX         KVM_X86_FEATURE(CPUID_7_1_EDX, 8)
 #define X86_FEATURE_PREFETCHITI         KVM_X86_FEATURE(CPUID_7_1_EDX, 14)
+#define X86_FEATURE_AVX10               KVM_X86_FEATURE(CPUID_7_1_EDX, 19)
 
 /* Intel-defined sub-features, CPUID level 0x00000007:2 (EDX) */
 #define X86_FEATURE_INTEL_PSFD		KVM_X86_FEATURE(CPUID_7_2_EDX, 0)
@@ -55,6 +57,11 @@ enum kvm_only_cpuid_leafs {
 #define KVM_X86_FEATURE_BHI_CTRL	KVM_X86_FEATURE(CPUID_7_2_EDX, 4)
 #define X86_FEATURE_MCDT_NO		KVM_X86_FEATURE(CPUID_7_2_EDX, 5)
 
+/* Intel-defined sub-features, CPUID level 0x00000024:0 (EBX) */
+#define X86_FEATURE_AVX10_128		KVM_X86_FEATURE(CPUID_24_0_EBX, 16)
+#define X86_FEATURE_AVX10_256		KVM_X86_FEATURE(CPUID_24_0_EBX, 17)
+#define X86_FEATURE_AVX10_512		KVM_X86_FEATURE(CPUID_24_0_EBX, 18)
+
 /* CPUID level 0x80000007 (EDX). */
 #define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
 
@@ -90,6 +97,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
 	[CPUID_8000_0022_EAX] = {0x80000022, 0, CPUID_EAX},
 	[CPUID_7_2_EDX]       = {         7, 2, CPUID_EDX},
+	[CPUID_24_0_EBX]      = {      0x24, 0, CPUID_EBX},
 };
 
 /*

arch/x86/kvm/smm.c

@@ -624,17 +624,31 @@ int emulator_leave_smm(struct x86_emulate_ctxt *ctxt)
 #endif
 
 	/*
-	 * Give leave_smm() a chance to make ISA-specific changes to the vCPU
-	 * state (e.g. enter guest mode) before loading state from the SMM
-	 * state-save area.
+	 * FIXME: When resuming L2 (a.k.a. guest mode), the transition to guest
+	 * mode should happen _after_ loading state from SMRAM.  However, KVM
+	 * piggybacks the nested VM-Enter flows (which is wrong for many other
+	 * reasons), and so nSVM/nVMX would clobber state that is loaded from
+	 * SMRAM and from the VMCS/VMCB.
 	 */
 	if (kvm_x86_call(leave_smm)(vcpu, &smram))
 		return X86EMUL_UNHANDLEABLE;
 
 #ifdef CONFIG_X86_64
 	if (guest_cpuid_has(vcpu, X86_FEATURE_LM))
-		return rsm_load_state_64(ctxt, &smram.smram64);
+		ret = rsm_load_state_64(ctxt, &smram.smram64);
 	else
 #endif
-		return rsm_load_state_32(ctxt, &smram.smram32);
+		ret = rsm_load_state_32(ctxt, &smram.smram32);
+
+	/*
+	 * If RSM fails and triggers shutdown, architecturally the shutdown
+	 * occurs *before* the transition to guest mode.  But due to KVM's
+	 * flawed handling of RSM to L2 (see above), the vCPU may already be
+	 * in_guest_mode().  Force the vCPU out of guest mode before delivering
+	 * the shutdown, so that L1 enters shutdown instead of seeing a VM-Exit
+	 * that architecturally shouldn't be possible.
+	 */
+	if (ret != X86EMUL_CONTINUE && is_guest_mode(vcpu))
+		kvm_leave_nested(vcpu);
+	return ret;
 }

arch/x86/kvm/svm/svm.c

@@ -2825,17 +2825,17 @@ static int efer_trap(struct kvm_vcpu *vcpu)
 	return kvm_complete_insn_gp(vcpu, ret);
 }
 
-static int svm_get_msr_feature(struct kvm_msr_entry *msr)
+static int svm_get_feature_msr(u32 msr, u64 *data)
 {
-	msr->data = 0;
+	*data = 0;
 
-	switch (msr->index) {
+	switch (msr) {
 	case MSR_AMD64_DE_CFG:
 		if (cpu_feature_enabled(X86_FEATURE_LFENCE_RDTSC))
-			msr->data |= MSR_AMD64_DE_CFG_LFENCE_SERIALIZE;
+			*data |= MSR_AMD64_DE_CFG_LFENCE_SERIALIZE;
 		break;
 	default:
-		return KVM_MSR_RET_INVALID;
+		return KVM_MSR_RET_UNSUPPORTED;
 	}
 
 	return 0;
@@ -3191,18 +3191,21 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		kvm_pr_unimpl_wrmsr(vcpu, ecx, data);
 		break;
 	case MSR_AMD64_DE_CFG: {
-		struct kvm_msr_entry msr_entry;
+		u64 supported_de_cfg;
 
-		msr_entry.index = msr->index;
-		if (svm_get_msr_feature(&msr_entry))
+		if (svm_get_feature_msr(ecx, &supported_de_cfg))
 			return 1;
 
-		/* Check the supported bits */
-		if (data & ~msr_entry.data)
+		if (data & ~supported_de_cfg)
 			return 1;
 
-		/* Don't allow the guest to change a bit, #GP */
-		if (!msr->host_initiated && (data ^ msr_entry.data))
+		/*
+		 * Don't let the guest change the host-programmed value.  The
+		 * MSR is very model specific, i.e. contains multiple bits that
+		 * are completely unknown to KVM, and the one bit known to KVM
+		 * is simply a reflection of hardware capabilities.
+		 */
+		if (!msr->host_initiated && data != svm->msr_decfg)
 			return 1;
 
 		svm->msr_decfg = data;
@@ -4156,12 +4159,21 @@ static int svm_vcpu_pre_run(struct kvm_vcpu *vcpu)
 
 static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 {
+	struct vcpu_svm *svm = to_svm(vcpu);
+
 	if (is_guest_mode(vcpu))
 		return EXIT_FASTPATH_NONE;
 
-	if (to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR &&
-	    to_svm(vcpu)->vmcb->control.exit_info_1)
+	switch (svm->vmcb->control.exit_code) {
+	case SVM_EXIT_MSR:
+		if (!svm->vmcb->control.exit_info_1)
+			break;
 		return handle_fastpath_set_msr_irqoff(vcpu);
+	case SVM_EXIT_HLT:
+		return handle_fastpath_hlt(vcpu);
+	default:
+		break;
+	}
 
 	return EXIT_FASTPATH_NONE;
 }
@@ -5012,7 +5024,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.vcpu_unblocking = avic_vcpu_unblocking,
 
 	.update_exception_bitmap = svm_update_exception_bitmap,
-	.get_msr_feature = svm_get_msr_feature,
+	.get_feature_msr = svm_get_feature_msr,
 	.get_msr = svm_get_msr,
 	.set_msr = svm_set_msr,
 	.get_segment_base = svm_get_segment_base,
@@ -5063,6 +5075,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.enable_nmi_window = svm_enable_nmi_window,
 	.enable_irq_window = svm_enable_irq_window,
 	.update_cr8_intercept = svm_update_cr8_intercept,
+
+	.x2apic_icr_is_split = true,
 	.set_virtual_apic_mode = avic_refresh_virtual_apic_mode,
 	.refresh_apicv_exec_ctrl = avic_refresh_apicv_exec_ctrl,
 	.apicv_post_state_restore = avic_apicv_post_state_restore,

arch/x86/kvm/vmx/main.c

@@ -43,7 +43,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.vcpu_put = vmx_vcpu_put,
 
 	.update_exception_bitmap = vmx_update_exception_bitmap,
-	.get_msr_feature = vmx_get_msr_feature,
+	.get_feature_msr = vmx_get_feature_msr,
 	.get_msr = vmx_get_msr,
 	.set_msr = vmx_set_msr,
 	.get_segment_base = vmx_get_segment_base,
@@ -91,6 +91,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.enable_nmi_window = vmx_enable_nmi_window,
 	.enable_irq_window = vmx_enable_irq_window,
 	.update_cr8_intercept = vmx_update_cr8_intercept,
+
+	.x2apic_icr_is_split = false,
 	.set_virtual_apic_mode = vmx_set_virtual_apic_mode,
 	.set_apic_access_page_addr = vmx_set_apic_access_page_addr,
 	.refresh_apicv_exec_ctrl = vmx_refresh_apicv_exec_ctrl,

arch/x86/kvm/vmx/vmx.c

@@ -1998,15 +1998,15 @@ static inline bool is_vmx_feature_control_msr_valid(struct vcpu_vmx *vmx,
 	return !(msr->data & ~valid_bits);
 }
 
-int vmx_get_msr_feature(struct kvm_msr_entry *msr)
+int vmx_get_feature_msr(u32 msr, u64 *data)
 {
-	switch (msr->index) {
+	switch (msr) {
 	case KVM_FIRST_EMULATED_VMX_MSR ... KVM_LAST_EMULATED_VMX_MSR:
 		if (!nested)
 			return 1;
-		return vmx_get_vmx_msr(&vmcs_config.nested, msr->index, &msr->data);
+		return vmx_get_vmx_msr(&vmcs_config.nested, msr, data);
 	default:
-		return KVM_MSR_RET_INVALID;
+		return KVM_MSR_RET_UNSUPPORTED;
 	}
 }
 
@@ -7265,6 +7265,8 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu,
 		return handle_fastpath_set_msr_irqoff(vcpu);
 	case EXIT_REASON_PREEMPTION_TIMER:
 		return handle_fastpath_preemption_timer(vcpu, force_immediate_exit);
+	case EXIT_REASON_HLT:
+		return handle_fastpath_hlt(vcpu);
 	default:
 		return EXIT_FASTPATH_NONE;
 	}

arch/x86/kvm/vmx/vmx.h

@@ -17,10 +17,6 @@
 #include "run_flags.h"
 #include "../mmu.h"
 
-#define MSR_TYPE_R	1
-#define MSR_TYPE_W	2
-#define MSR_TYPE_RW	3
-
 #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
 
 #ifdef CONFIG_X86_64

arch/x86/kvm/vmx/x86_ops.h

@@ -57,7 +57,7 @@ bool vmx_has_emulated_msr(struct kvm *kvm, u32 index);
 void vmx_msr_filter_changed(struct kvm_vcpu *vcpu);
 void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
 void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu);
-int vmx_get_msr_feature(struct kvm_msr_entry *msr);
+int vmx_get_feature_msr(u32 msr, u64 *data);
 int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
 u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg);
 void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);

arch/x86/kvm/x86.h

@@ -108,6 +108,12 @@ static inline unsigned int __shrink_ple_window(unsigned int val,
 void kvm_service_local_tlb_flush_requests(struct kvm_vcpu *vcpu);
 int kvm_check_nested_events(struct kvm_vcpu *vcpu);
 
+/* Forcibly leave the nested mode in cases like a vCPU reset */
+static inline void kvm_leave_nested(struct kvm_vcpu *vcpu)
+{
+	kvm_x86_ops.nested_ops->leave_nested(vcpu);
+}
+
 static inline bool kvm_vcpu_has_run(struct kvm_vcpu *vcpu)
 {
 	return vcpu->arch.last_vmentry_cpu != -1;
@@ -334,6 +340,7 @@ int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len);
 fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
+fastpath_t handle_fastpath_hlt(struct kvm_vcpu *vcpu);
 
 extern struct kvm_caps kvm_caps;
 extern struct kvm_host_values kvm_host;
@@ -504,13 +511,26 @@ int kvm_handle_memory_failure(struct kvm_vcpu *vcpu, int r,
 int kvm_handle_invpcid(struct kvm_vcpu *vcpu, unsigned long type, gva_t gva);
 bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type);
 
+enum kvm_msr_access {
+	MSR_TYPE_R	= BIT(0),
+	MSR_TYPE_W	= BIT(1),
+	MSR_TYPE_RW	= MSR_TYPE_R | MSR_TYPE_W,
+};
+
 /*
  * Internal error codes that are used to indicate that MSR emulation encountered
- * an error that should result in #GP in the guest, unless userspace
- * handles it.
+ * an error that should result in #GP in the guest, unless userspace handles it.
+ * Note, '1', '0', and negative numbers are off limits, as they are used by KVM
+ * as part of KVM's lightly documented internal KVM_RUN return codes.
+ *
+ * UNSUPPORTED	- The MSR isn't supported, either because it is completely
+ *		  unknown to KVM, or because the MSR should not exist according
+ *		  to the vCPU model.
+ *
+ * FILTERED	- Access to the MSR is denied by a userspace MSR filter.
  */
-#define  KVM_MSR_RET_INVALID	2	/* in-kernel MSR emulation #GP condition */
-#define  KVM_MSR_RET_FILTERED	3	/* #GP due to userspace MSR filter */
+#define  KVM_MSR_RET_UNSUPPORTED	2
+#define  KVM_MSR_RET_FILTERED		3
 
 #define __cr4_reserved_bits(__cpu_has, __c)             \
 ({                                                      \

tools/testing/selftests/kvm/guest_print_test.c

@@ -107,6 +107,21 @@ static void ucall_abort(const char *assert_msg, const char *expected_assert_msg)
 		    expected_assert_msg, &assert_msg[offset]);
 }
 
+/*
+ * Open code vcpu_run(), sans the UCALL_ABORT handling, so that intentional
+ * guest asserts guest can be verified instead of being reported as failures.
+ */
+static void do_vcpu_run(struct kvm_vcpu *vcpu)
+{
+	int r;
+
+	do {
+		r = __vcpu_run(vcpu);
+	} while (r == -1 && errno == EINTR);
+
+	TEST_ASSERT(!r, KVM_IOCTL_ERROR(KVM_RUN, r));
+}
+
 static void run_test(struct kvm_vcpu *vcpu, const char *expected_printf,
 		     const char *expected_assert)
 {
@@ -114,7 +129,7 @@ static void run_test(struct kvm_vcpu *vcpu, const char *expected_printf,
 	struct ucall uc;
 
 	while (1) {
-		vcpu_run(vcpu);
+		do_vcpu_run(vcpu);
 
 		TEST_ASSERT(run->exit_reason == UCALL_EXIT_REASON,
 			    "Unexpected exit reason: %u (%s),",
@@ -159,7 +174,7 @@ static void test_limits(void)
 
 	vm = vm_create_with_one_vcpu(&vcpu, guest_code_limits);
 	run = vcpu->run;
-	vcpu_run(vcpu);
+	do_vcpu_run(vcpu);
 
 	TEST_ASSERT(run->exit_reason == UCALL_EXIT_REASON,
 		    "Unexpected exit reason: %u (%s),",

tools/testing/selftests/kvm/include/x86_64/apic.h

@@ -11,6 +11,7 @@
 #include <stdint.h>
 
 #include "processor.h"
+#include "ucall_common.h"
 
 #define APIC_DEFAULT_GPA		0xfee00000ULL
 
@@ -93,9 +94,27 @@ static inline uint64_t x2apic_read_reg(unsigned int reg)
 	return rdmsr(APIC_BASE_MSR + (reg >> 4));
 }
 
+static inline uint8_t x2apic_write_reg_safe(unsigned int reg, uint64_t value)
+{
+	return wrmsr_safe(APIC_BASE_MSR + (reg >> 4), value);
+}
+
 static inline void x2apic_write_reg(unsigned int reg, uint64_t value)
 {
-	wrmsr(APIC_BASE_MSR + (reg >> 4), value);
+	uint8_t fault = x2apic_write_reg_safe(reg, value);
+
+	__GUEST_ASSERT(!fault, "Unexpected fault 0x%x on WRMSR(%x) = %lx\n",
+		       fault, APIC_BASE_MSR + (reg >> 4), value);
 }
 
+static inline void x2apic_write_reg_fault(unsigned int reg, uint64_t value)
+{
+	uint8_t fault = x2apic_write_reg_safe(reg, value);
+
+	__GUEST_ASSERT(fault == GP_VECTOR,
+		       "Wanted #GP on WRMSR(%x) = %lx, got 0x%x\n",
+		       APIC_BASE_MSR + (reg >> 4), value, fault);
+}
+
+
 #endif /* SELFTEST_KVM_APIC_H */

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -566,9 +566,7 @@ void route_exception(struct ex_regs *regs)
 	if (kvm_fixup_exception(regs))
 		return;
 
-	ucall_assert(UCALL_UNHANDLED,
-		     "Unhandled exception in guest", __FILE__, __LINE__,
-		     "Unhandled exception '0x%lx' at guest RIP '0x%lx'",
+	GUEST_FAIL("Unhandled exception '0x%lx' at guest RIP '0x%lx'",
 		   regs->vector, regs->rip);
 }
 
@@ -611,7 +609,7 @@ void assert_on_unhandled_exception(struct kvm_vcpu *vcpu)
 {
 	struct ucall uc;
 
-	if (get_ucall(vcpu, &uc) == UCALL_UNHANDLED)
+	if (get_ucall(vcpu, &uc) == UCALL_ABORT)
 		REPORT_GUEST_ASSERT(uc);
 }
 

tools/testing/selftests/kvm/x86_64/xapic_state_test.c

@@ -13,6 +13,7 @@
 struct xapic_vcpu {
 	struct kvm_vcpu *vcpu;
 	bool is_x2apic;
+	bool has_xavic_errata;
 };
 
 static void xapic_guest_code(void)
@@ -31,6 +32,10 @@ static void xapic_guest_code(void)
 	}
 }
 
+#define X2APIC_RSVD_BITS_MASK  (GENMASK_ULL(31, 20) | \
+				GENMASK_ULL(17, 16) | \
+				GENMASK_ULL(13, 13))
+
 static void x2apic_guest_code(void)
 {
 	asm volatile("cli");
@@ -41,7 +46,12 @@ static void x2apic_guest_code(void)
 		uint64_t val = x2apic_read_reg(APIC_IRR) |
 			       x2apic_read_reg(APIC_IRR + 0x10) << 32;
 
+		if (val & X2APIC_RSVD_BITS_MASK) {
+			x2apic_write_reg_fault(APIC_ICR, val);
+		} else {
 			x2apic_write_reg(APIC_ICR, val);
+			GUEST_ASSERT_EQ(x2apic_read_reg(APIC_ICR), val);
+		}
 		GUEST_SYNC(val);
 	} while (1);
 }
@@ -71,27 +81,28 @@ static void ____test_icr(struct xapic_vcpu *x, uint64_t val)
 	icr = (u64)(*((u32 *)&xapic.regs[APIC_ICR])) |
 	      (u64)(*((u32 *)&xapic.regs[APIC_ICR2])) << 32;
 	if (!x->is_x2apic) {
+		if (!x->has_xavic_errata)
 			val &= (-1u | (0xffull << (32 + 24)));
-		TEST_ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
-	} else {
-		TEST_ASSERT_EQ(icr & ~APIC_ICR_BUSY, val & ~APIC_ICR_BUSY);
+	} else if (val & X2APIC_RSVD_BITS_MASK) {
+		return;
 	}
-}
 
-#define X2APIC_RSVED_BITS_MASK  (GENMASK_ULL(31,20) | \
-				 GENMASK_ULL(17,16) | \
-				 GENMASK_ULL(13,13))
+	if (x->has_xavic_errata)
+		TEST_ASSERT_EQ(icr & ~APIC_ICR_BUSY, val & ~APIC_ICR_BUSY);
+	else
+		TEST_ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
+}
 
 static void __test_icr(struct xapic_vcpu *x, uint64_t val)
 {
-	if (x->is_x2apic) {
-		/* Hardware writing vICR register requires reserved bits 31:20,
-		 * 17:16 and 13 kept as zero to avoid #GP exception. Data value
-		 * written to vICR should mask out those bits above.
+	/*
+	 * The BUSY bit is reserved on both AMD and Intel, but only AMD treats
+	 * it is as _must_ be zero.  Intel simply ignores the bit.  Don't test
+	 * the BUSY bit for x2APIC, as there is no single correct behavior.
 	 */
-		val &= ~X2APIC_RSVED_BITS_MASK;
-	}
+	if (!x->is_x2apic)
 		____test_icr(x, val | APIC_ICR_BUSY);
+
 	____test_icr(x, val & ~(u64)APIC_ICR_BUSY);
 }
 
@@ -231,6 +242,15 @@ int main(int argc, char *argv[])
 	vm = vm_create_with_one_vcpu(&x.vcpu, xapic_guest_code);
 	x.is_x2apic = false;
 
+	/*
+	 * AMD's AVIC implementation is buggy (fails to clear the ICR BUSY bit),
+	 * and also diverges from KVM with respect to ICR2[23:0] (KVM and Intel
+	 * drops writes, AMD does not).  Account for the errata when checking
+	 * that KVM reads back what was written.
+	 */
+	x.has_xavic_errata = host_cpu_is_amd &&
+			     get_kvm_amd_param_bool("avic");
+
 	vcpu_clear_cpuid_feature(x.vcpu, X86_FEATURE_X2APIC);
 
 	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);