KVM: nVMX: Don't leak L1 MMIO regions to L2

PATCH Superseded Jim Mattson 2 participants 6 messages Oct 10, 2019 – Oct 14, 2019

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Jim Mattson

author

2019-10-10 23:28 UTC #0 lore raw

PATCH v3 1/1 KVM: nVMX: Don't leak L1 MMIO regions to L2

If the "virtualize APIC accesses" VM-execution control is set in the VMCS, the APIC virtualization hardware is triggered when a page walk in VMX non-root mode terminates at a PTE wherein the address of the 4k page frame matches the APIC-access address specified in the VMCS. On hardware, the APIC-access address may be any valid 4k-aligned physical address.

KVM's nVMX implementation enforces the additional constraint that the APIC-access address specified in the vmcs12 must be backed by cacheable memory in L1. If not, L0 will simply clear the "virtualize APIC accesses" VM-execution control in the vmcs02.

The problem with this approach is that the L1 guest has arranged the vmcs12 EPT tables--or shadow page tables, if the "enable EPT" VM-execution control is clear in the vmcs12--so that the L2 guest physical address(es)--or L2 guest linear address(es)--that reference the L2 APIC map to the APIC-access address specified in the vmcs12. Without the "virtualize APIC accesses" VM-execution control in the vmcs02, the APIC accesses in the L2 guest will directly access the APIC-access page in L1.

When there is no mapping whatsoever for the APIC-access address in L1, the L2 VM just loses the intended APIC virtualization. However, when the APIC-access address is mapped to an MMIO region in L1, the L2 guest gets direct access to the L1 MMIO device. For example, if the APIC-access address specified in the vmcs12 is 0xfee00000, then L2 gets direct access to L1's APIC.

Since this vmcs12 configuration is something that KVM cannot faithfully emulate, the appropriate response is to exit to userspace with KVM_INTERNAL_ERROR_EMULATION.

Fixes fe3ef05c7572 ("KVM: nVMX: Prepare vmcs02 from vmcs01 and vmcs12")

Reported-by Dan Cross <[email protected]>

Signed-off-by Jim Mattson <[email protected]>

Reviewed-by Peter Shier <[email protected]>

Change-Id Ib501fe63266c1d831ce4d1d55e8688bc34a6844a

---
v2 -> v3: Added default case to new switch in nested_vmx_run v1 -> v2: Added enum enter_vmx_status

 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/vmx/nested.c       | 68 +++++++++++++++++++--------------
 arch/x86/kvm/vmx/nested.h       | 13 ++++++-
 arch/x86/kvm/x86.c              |  8 +++-
 4 files changed, 59 insertions(+), 32 deletions(-)

arch/x86/include/asm/kvm_host.h +1 -1

index 5d8056ff7390..0dee68560437 100644
@@ -1186,7 +1186,7 @@ struct kvm_x86_ops {
 	int (*set_nested_state)(struct kvm_vcpu *vcpu,
 				struct kvm_nested_state __user *user_kvm_nested_state,
 				struct kvm_nested_state *kvm_state);
-	void (*get_vmcs12_pages)(struct kvm_vcpu *vcpu);
+	bool (*get_vmcs12_pages)(struct kvm_vcpu *vcpu);
 
 	int (*smi_allowed)(struct kvm_vcpu *vcpu);
 	int (*pre_enter_smm)(struct kvm_vcpu *vcpu, char *smstate);

arch/x86/kvm/vmx/nested.c +40 ~~-28~~

139 lines not on this page · raw message

arch/x86/kvm/vmx/nested.h +12 -1

index 187d39bf0bf1..07cf5cef86f6 100644
@@ -6,6 +6,16 @@
 #include "vmcs12.h"
 #include "vmx.h"
 
+/*
+ * Status returned by nested_vmx_enter_non_root_mode():
+ */
+enum enter_vmx_status {
+	ENTER_VMX_SUCCESS,	/* Successfully entered VMX non-root mode */
+	ENTER_VMX_VMFAIL,	/* Consistency check VMFail */
+	ENTER_VMX_VMEXIT,	/* Consistency check VMExit */
+	ENTER_VMX_ERROR,	/* KVM internal error */
+};
+
 void vmx_leave_nested(struct kvm_vcpu *vcpu);
 void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps,
 				bool apicv);

@@ -13,7 +23,8 @@ void nested_vmx_hardware_unsetup(void);
 __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *));
 void nested_vmx_vcpu_setup(void);
 void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu);
-int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry);
+enum enter_vmx_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
+						     bool from_vmentry);
 bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason);
 void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 		       u32 exit_intr_info, unsigned long exit_qualification);

arch/x86/kvm/x86.c +6 -2

index f26f8be4e621..627fd7ff3a28 100644
@@ -7937,8 +7937,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	bool req_immediate_exit = false;
 
 	if (kvm_request_pending(vcpu)) {
-		if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu))
-			kvm_x86_ops->get_vmcs12_pages(vcpu);
+		if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu)) {
+			if (unlikely(!kvm_x86_ops->get_vmcs12_pages(vcpu))) {
+				r = 0;
+				goto out;
+			}
+		}
 		if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
 			kvm_mmu_unload(vcpu);
 		if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))

Signature · 1 line

2.23.0.581.g78d2f28ef7-goog

Sean Christopherson

2019-10-14 17:59 UTC #1 lore raw

Quoted 82 lines · Jim Mattson

If the "virtualize APIC accesses" VM-execution control is set in the VMCS, the APIC virtualization hardware is triggered when a page walk in VMX non-root mode terminates at a PTE wherein the address of the 4k page frame matches the APIC-access address specified in the VMCS. On hardware, the APIC-access address may be any valid 4k-aligned physical address.
KVM's nVMX implementation enforces the additional constraint that the APIC-access address specified in the vmcs12 must be backed by cacheable memory in L1. If not, L0 will simply clear the "virtualize APIC accesses" VM-execution control in the vmcs02.
The problem with this approach is that the L1 guest has arranged the vmcs12 EPT tables--or shadow page tables, if the "enable EPT" VM-execution control is clear in the vmcs12--so that the L2 guest physical address(es)--or L2 guest linear address(es)--that reference the L2 APIC map to the APIC-access address specified in the vmcs12. Without the "virtualize APIC accesses" VM-execution control in the vmcs02, the APIC accesses in the L2 guest will directly access the APIC-access page in L1.
When there is no mapping whatsoever for the APIC-access address in L1, the L2 VM just loses the intended APIC virtualization. However, when the APIC-access address is mapped to an MMIO region in L1, the L2 guest gets direct access to the L1 MMIO device. For example, if the APIC-access address specified in the vmcs12 is 0xfee00000, then L2 gets direct access to L1's APIC.
Since this vmcs12 configuration is something that KVM cannot faithfully emulate, the appropriate response is to exit to userspace with KVM_INTERNAL_ERROR_EMULATION.
Fixes fe3ef05c7572 ("KVM: nVMX: Prepare vmcs02 from vmcs01 and vmcs12")
Reported-by Dan Cross <[email protected]>
Signed-off-by Jim Mattson <[email protected]>
Reviewed-by Peter Shier <[email protected]>
Change-Id Ib501fe63266c1d831ce4d1d55e8688bc34a6844a
---
v2 -> v3: Added default case to new switch in nested_vmx_run v1 -> v2: Added enum enter_vmx_status
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/vmx/nested.c       | 68 +++++++++++++++++++--------------
 arch/x86/kvm/vmx/nested.h       | 13 ++++++-
 arch/x86/kvm/x86.c              |  8 +++-
 4 files changed, 59 insertions(+), 32 deletions(-)
arch/x86/include/asm/kvm_host.h +1 -1
index 5d8056ff7390..0dee68560437 100644
@@ -1186,7 +1186,7 @@ struct kvm_x86_ops {
 	int (*set_nested_state)(struct kvm_vcpu *vcpu,
 				struct kvm_nested_state __user *user_kvm_nested_state,
 				struct kvm_nested_state *kvm_state);
-	void (*get_vmcs12_pages)(struct kvm_vcpu *vcpu);
+	bool (*get_vmcs12_pages)(struct kvm_vcpu *vcpu);
 
 	int (*smi_allowed)(struct kvm_vcpu *vcpu);
 	int (*pre_enter_smm)(struct kvm_vcpu *vcpu, char *smstate);
arch/x86/kvm/vmx/nested.c +1 -6
index 5e231da00310..88b2f08aaaae 100644
@@ -2927,7 +2927,7 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
 static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
 						 struct vmcs12 *vmcs12);
 
-static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
+static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 {
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -2947,19 +2947,18 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 			vmx->nested.apic_access_page = NULL;
 		}
 		page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->apic_access_addr);
-		/*
-		 * If translation failed, no matter: This feature asks
-		 * to exit when accessing the given address, and if it
-		 * can never be accessed, this feature won't do
-		 * anything anyway.

arch/x86/kvm/vmx/nested.c static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu) · line 2956

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +2 -3

-		 */
 		if (!is_error_page(page)) {
 			vmx->nested.apic_access_page = page;
 			hpa = page_to_phys(vmx->nested.apic_access_page);
 			vmcs_write64(APIC_ACCESS_ADDR, hpa);
 		} else {
-			secondary_exec_controls_clearbit(vmx,
-				SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES);
+			pr_debug_ratelimited("%s: non-cacheable APIC-access address in vmcs12\n",
+					     __func__);

Hmm, "non-cacheable" is confusing, especially in the context of the APIC, which needs to be mapped "uncacheable". Maybe just "invalid"?

Quoted 18 lines

arch/x86/kvm/vmx/nested.c +6 -0

+			vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+			vcpu->run->internal.suberror =
+				KVM_INTERNAL_ERROR_EMULATION;
+			vcpu->run->internal.ndata = 0;
+			return false;
 		}
 	}

@@ -3004,6 +3003,7 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 		exec_controls_setbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
 	else
 		exec_controls_clearbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
+	return true;
 }
 
 /*

@@ -3042,13 +3042,15 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 /*

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3047

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +3 -5

  * If from_vmentry is false, this is being called from state restore (either RSM
  * or KVM_SET_NESTED_STATE).  Otherwise it's called from vmlaunch/vmresume.
-+ *
-+ * Returns:
-+ *   0 - success, i.e. proceed with actual VMEnter
-+ *   1 - consistency check VMExit
-+ *  -1 - consistency check VMFail
+ *
+ * Returns:
+ *	ENTER_VMX_SUCCESS: Successfully entered VMX non-root mode

"Enter VMX" usually refers to VMXON, e.g. the title of VMXON in the SDM is "Enter VMX Operation".

Maybe NVMX_ENTER_NON_ROOT_?

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3050

Quoted 3 lines

arch/x86/kvm/vmx/nested.c +3 -0

+ *	ENTER_VMX_VMFAIL:  Consistency check VMFail
+ *	ENTER_VMX_VMEXIT:  Consistency check VMExit
+ *	ENTER_VMX_ERROR:   KVM internal error

Probably need to more explicit than VMX_ERROR, e.g. all of the VM-Fail defines are prefixed with VMXERR_##.

May ENTER_VMX_KVM_ERROR? (Or NVMX_ENTER_NON_ROOT_KVM_ERROR).

Quoted 61 lines

arch/x86/kvm/vmx/nested.c +9 -7

  */
-int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
+enum enter_vmx_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
+						     bool from_vmentry)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);

@@ -3091,11 +3093,12 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 	prepare_vmcs02_early(vmx, vmcs12);
 
 	if (from_vmentry) {
-		nested_get_vmcs12_pages(vcpu);
+		if (unlikely(!nested_get_vmcs12_pages(vcpu)))
+			return ENTER_VMX_ERROR;
 
 		if (nested_vmx_check_vmentry_hw(vcpu)) {
 			vmx_switch_vmcs(vcpu, &vmx->vmcs01);
-			return -1;
+			return ENTER_VMX_VMFAIL;
 		}
 
 		if (nested_vmx_check_guest_state(vcpu, vmcs12, &exit_qual))

@@ -3159,7 +3162,7 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 	 * returned as far as L1 is concerned. It will only return (and set
 	 * the success flag) when L2 exits (see nested_vmx_vmexit()).
 	 */
-	return 0;
+	return ENTER_VMX_SUCCESS;
 
 	/*
 	 * A failed consistency check that leads to a VMExit during L1's

@@ -3175,14 +3178,14 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 	vmx_switch_vmcs(vcpu, &vmx->vmcs01);
 
 	if (!from_vmentry)
-		return 1;
+		return ENTER_VMX_VMEXIT;
 
 	load_vmcs12_host_state(vcpu, vmcs12);
 	vmcs12->vm_exit_reason = exit_reason | VMX_EXIT_REASONS_FAILED_VMENTRY;
 	vmcs12->exit_qualification = exit_qual;
 	if (enable_shadow_vmcs || vmx->nested.hv_evmcs)
 		vmx->nested.need_vmcs12_to_shadow_sync = true;
-	return 1;
+	return ENTER_VMX_VMEXIT;
 }
 
 /*

@@ -3192,9 +3195,9 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 {
 	struct vmcs12 *vmcs12;
+	enum enter_vmx_status status;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	u32 interrupt_shadow = vmx_get_interrupt_shadow(vcpu);
-	int ret;
 
 	if (!nested_vmx_check_permission(vcpu))
 		return 1;

@@ -3254,13 +3257,22 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	 * the nested entry.

arch/x86/kvm/vmx/nested.c static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) · line 3260

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +1 -7

 	 */
 	vmx->nested.nested_run_pending = 1;
-	ret = nested_vmx_enter_non_root_mode(vcpu, true);
-	vmx->nested.nested_run_pending = !ret;
-	if (ret > 0)
-		return 1;
-	else if (ret)
-		return nested_vmx_failValid(vcpu,
-			VMXERR_ENTRY_INVALID_CONTROL_FIELD);
+	status = nested_vmx_enter_non_root_mode(vcpu, true);

What if we use a goto to bury the error handling at the end? That'd also provide some flexibility with respect to handling each failure, e.g.:

	vmx->nested.nested_run_pending = 1;
	status = nested_vmx_enter_non_root_mode(vcpu, true);
	if (status != ENTER_VMX_SUCCESS)
		goto vmenter_failed;

	...

	return 1;

vmenter_failed:

	vmx->nested.nested_run_pending = 0;
	if (status == ENTER_VMX_VMFAIL)
		return nested_vmx_failValid(vcpu,
					    VMXERR_ENTRY_INVALID_CONTROL_FIELD);

	return status == ENTER_VMX_ERROR ? 0 : 1;

	vmx->nested.nested_run_pending = 1;
	status = nested_vmx_enter_non_root_mode(vcpu, true);
	if (status != ENTER_VMX_SUCCESS)
		goto vmenter_failed;

	...

	return 1;

vmenter_failed:

	vmx->nested.nested_run_pending = 0;
	if (status == ENTER_VMX_ERROR)
		return 0;
	if (status == ENTER_VMX_VMEXIT)
		return 1;

	WARN_ON_ONCE(status != ENTER_VMX_VMFAIL);
	return nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);

Quoted 71 lines

arch/x86/kvm/vmx/nested.c +15 -0

+	if (status != ENTER_VMX_SUCCESS) {
+		vmx->nested.nested_run_pending = 0;
+		switch (status) {
+		case ENTER_VMX_VMFAIL:
+			return nested_vmx_failValid(vcpu,
+				VMXERR_ENTRY_INVALID_CONTROL_FIELD);
+		case ENTER_VMX_VMEXIT:
+			return 1;
+		case ENTER_VMX_ERROR:
+			return 0;
+		default:
+			WARN_ON_ONCE(1);
+			break;
+		}
+	}
 
 	/* Hide L1D cache contents from the nested guest.  */
 	vmx->vcpu.arch.l1tf_flush_l1d = true;

arch/x86/kvm/vmx/nested.h +12 -1

index 187d39bf0bf1..07cf5cef86f6 100644
@@ -6,6 +6,16 @@
 #include "vmcs12.h"
 #include "vmx.h"
 
+/*
+ * Status returned by nested_vmx_enter_non_root_mode():
+ */
+enum enter_vmx_status {
+	ENTER_VMX_SUCCESS,	/* Successfully entered VMX non-root mode */
+	ENTER_VMX_VMFAIL,	/* Consistency check VMFail */
+	ENTER_VMX_VMEXIT,	/* Consistency check VMExit */
+	ENTER_VMX_ERROR,	/* KVM internal error */
+};
+
 void vmx_leave_nested(struct kvm_vcpu *vcpu);
 void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps,
 				bool apicv);

@@ -13,7 +23,8 @@ void nested_vmx_hardware_unsetup(void);
 __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *));
 void nested_vmx_vcpu_setup(void);
 void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu);
-int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry);
+enum enter_vmx_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
+						     bool from_vmentry);
 bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason);
 void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 		       u32 exit_intr_info, unsigned long exit_qualification);

arch/x86/kvm/x86.c +6 -2

index f26f8be4e621..627fd7ff3a28 100644
@@ -7937,8 +7937,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	bool req_immediate_exit = false;
 
 	if (kvm_request_pending(vcpu)) {
-		if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu))
-			kvm_x86_ops->get_vmcs12_pages(vcpu);
+		if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu)) {
+			if (unlikely(!kvm_x86_ops->get_vmcs12_pages(vcpu))) {
+				r = 0;
+				goto out;
+			}
+		}
 		if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
 			kvm_mmu_unload(vcpu);
 		if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))

Signature · 1 line

2.23.0.581.g78d2f28ef7-goog

Jim Mattson

author

2019-10-14 18:50 UTC #2 lore raw

Quoted 89 lines · Sean Christopherson

Quoted 87 lines · Jim Mattson
If the "virtualize APIC accesses" VM-execution control is set in the VMCS, the APIC virtualization hardware is triggered when a page walk in VMX non-root mode terminates at a PTE wherein the address of the 4k page frame matches the APIC-access address specified in the VMCS. On hardware, the APIC-access address may be any valid 4k-aligned physical address.
KVM's nVMX implementation enforces the additional constraint that the APIC-access address specified in the vmcs12 must be backed by cacheable memory in L1. If not, L0 will simply clear the "virtualize APIC accesses" VM-execution control in the vmcs02.
The problem with this approach is that the L1 guest has arranged the vmcs12 EPT tables--or shadow page tables, if the "enable EPT" VM-execution control is clear in the vmcs12--so that the L2 guest physical address(es)--or L2 guest linear address(es)--that reference the L2 APIC map to the APIC-access address specified in the vmcs12. Without the "virtualize APIC accesses" VM-execution control in the vmcs02, the APIC accesses in the L2 guest will directly access the APIC-access page in L1.
When there is no mapping whatsoever for the APIC-access address in L1, the L2 VM just loses the intended APIC virtualization. However, when the APIC-access address is mapped to an MMIO region in L1, the L2 guest gets direct access to the L1 MMIO device. For example, if the APIC-access address specified in the vmcs12 is 0xfee00000, then L2 gets direct access to L1's APIC.
Since this vmcs12 configuration is something that KVM cannot faithfully emulate, the appropriate response is to exit to userspace with KVM_INTERNAL_ERROR_EMULATION.
Fixes fe3ef05c7572 ("KVM: nVMX: Prepare vmcs02 from vmcs01 and vmcs12")
Reported-by Dan Cross <[email protected]>
Signed-off-by Jim Mattson <[email protected]>
Reviewed-by Peter Shier <[email protected]>
Change-Id Ib501fe63266c1d831ce4d1d55e8688bc34a6844a
---
v2 -> v3: Added default case to new switch in nested_vmx_run v1 -> v2: Added enum enter_vmx_status
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/vmx/nested.c       | 68 +++++++++++++++++++--------------
 arch/x86/kvm/vmx/nested.h       | 13 ++++++-
 arch/x86/kvm/x86.c              |  8 +++-
 4 files changed, 59 insertions(+), 32 deletions(-)
arch/x86/include/asm/kvm_host.h +1 -1
index 5d8056ff7390..0dee68560437 100644
@@ -1186,7 +1186,7 @@ struct kvm_x86_ops {
      int (*set_nested_state)(struct kvm_vcpu *vcpu,
                              struct kvm_nested_state __user *user_kvm_nested_state,
                              struct kvm_nested_state *kvm_state);
-     void (*get_vmcs12_pages)(struct kvm_vcpu *vcpu);
+     bool (*get_vmcs12_pages)(struct kvm_vcpu *vcpu);
 
      int (*smi_allowed)(struct kvm_vcpu *vcpu);
      int (*pre_enter_smm)(struct kvm_vcpu *vcpu, char *smstate);
arch/x86/kvm/vmx/nested.c +1 -7
index 5e231da00310..88b2f08aaaae 100644
@@ -2927,7 +2927,7 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
 static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
                                               struct vmcs12 *vmcs12);
 
-static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
+static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 {
      struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
      struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -2947,19 +2947,18 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
                      vmx->nested.apic_access_page = NULL;
              }
              page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->apic_access_addr);
-             /*
-              * If translation failed, no matter: This feature asks
-              * to exit when accessing the given address, and if it
-              * can never be accessed, this feature won't do
-              * anything anyway.
-              */
              if (!is_error_page(page)) {
                      vmx->nested.apic_access_page = page;
                      hpa = page_to_phys(vmx->nested.apic_access_page);
                      vmcs_write64(APIC_ACCESS_ADDR, hpa);

Quoted 8 lines

arch/x86/kvm/vmx/nested.c static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu) · line 2956
Quoted 5 lines
arch/x86/kvm/vmx/nested.c +2 -2
              } else {
-                     secondary_exec_controls_clearbit(vmx,
-                             SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES);
+                     pr_debug_ratelimited("%s: non-cacheable APIC-access address in vmcs12\n",
+                                          __func__);
Hmm, "non-cacheable" is confusing, especially in the context of the APIC, which needs to be mapped "uncacheable". Maybe just "invalid"?

"Invalid" is not correct. L1 MMIO addresses are valid; they're just not cacheable. Perhaps:

"vmcs12 APIC-access address references a page not backed by a memslot in L1"?

Quoted 32 lines

Quoted 18 lines

arch/x86/kvm/vmx/nested.c +6 -0

+                     vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+                     vcpu->run->internal.suberror =
+                             KVM_INTERNAL_ERROR_EMULATION;
+                     vcpu->run->internal.ndata = 0;
+                     return false;
              }
      }

@@ -3004,6 +3003,7 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
              exec_controls_setbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
      else
              exec_controls_clearbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
+     return true;
 }
 
 /*

@@ -3042,13 +3042,15 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 /*

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3047

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +3 -5

  * If from_vmentry is false, this is being called from state restore (either RSM
  * or KVM_SET_NESTED_STATE).  Otherwise it's called from vmlaunch/vmresume.
-+ *
-+ * Returns:
-+ *   0 - success, i.e. proceed with actual VMEnter
-+ *   1 - consistency check VMExit
-+ *  -1 - consistency check VMFail
+ *
+ * Returns:
+ *   ENTER_VMX_SUCCESS: Successfully entered VMX non-root mode

"Enter VMX" usually refers to VMXON, e.g. the title of VMXON in the SDM is "Enter VMX Operation".

Quoted 1 line

Maybe NVMX_ENTER_NON_ROOT_?

How about NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_?

Quoted 8 lines

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3050
Quoted 3 lines
arch/x86/kvm/vmx/nested.c +3 -0
+ *   ENTER_VMX_VMFAIL:  Consistency check VMFail
+ *   ENTER_VMX_VMEXIT:  Consistency check VMExit
+ *   ENTER_VMX_ERROR:   KVM internal error
Probably need to more explicit than VMX_ERROR, e.g. all of the VM-Fail defines are prefixed with VMXERR_##.
May ENTER_VMX_KVM_ERROR? (Or NVMX_ENTER_NON_ROOT_KVM_ERROR).

NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_KVM_INTERNAL_ERROR?

Quoted 104 lines

Quoted 61 lines

arch/x86/kvm/vmx/nested.c +9 -7

  */
-int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
+enum enter_vmx_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
+                                                  bool from_vmentry)
 {
      struct vcpu_vmx *vmx = to_vmx(vcpu);
      struct vmcs12 *vmcs12 = get_vmcs12(vcpu);

@@ -3091,11 +3093,12 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
      prepare_vmcs02_early(vmx, vmcs12);
 
      if (from_vmentry) {
-             nested_get_vmcs12_pages(vcpu);
+             if (unlikely(!nested_get_vmcs12_pages(vcpu)))
+                     return ENTER_VMX_ERROR;
 
              if (nested_vmx_check_vmentry_hw(vcpu)) {
                      vmx_switch_vmcs(vcpu, &vmx->vmcs01);
-                     return -1;
+                     return ENTER_VMX_VMFAIL;
              }
 
              if (nested_vmx_check_guest_state(vcpu, vmcs12, &exit_qual))

@@ -3159,7 +3162,7 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
       * returned as far as L1 is concerned. It will only return (and set
       * the success flag) when L2 exits (see nested_vmx_vmexit()).
       */
-     return 0;
+     return ENTER_VMX_SUCCESS;
 
      /*
       * A failed consistency check that leads to a VMExit during L1's

@@ -3175,14 +3178,14 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
      vmx_switch_vmcs(vcpu, &vmx->vmcs01);
 
      if (!from_vmentry)
-             return 1;
+             return ENTER_VMX_VMEXIT;
 
      load_vmcs12_host_state(vcpu, vmcs12);
      vmcs12->vm_exit_reason = exit_reason | VMX_EXIT_REASONS_FAILED_VMENTRY;
      vmcs12->exit_qualification = exit_qual;
      if (enable_shadow_vmcs || vmx->nested.hv_evmcs)
              vmx->nested.need_vmcs12_to_shadow_sync = true;
-     return 1;
+     return ENTER_VMX_VMEXIT;
 }
 
 /*

@@ -3192,9 +3195,9 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 {
      struct vmcs12 *vmcs12;
+     enum enter_vmx_status status;
      struct vcpu_vmx *vmx = to_vmx(vcpu);
      u32 interrupt_shadow = vmx_get_interrupt_shadow(vcpu);
-     int ret;
 
      if (!nested_vmx_check_permission(vcpu))
              return 1;

@@ -3254,13 +3257,22 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
       * the nested entry.

arch/x86/kvm/vmx/nested.c static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) · line 3260

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +1 -7

       */
      vmx->nested.nested_run_pending = 1;
-     ret = nested_vmx_enter_non_root_mode(vcpu, true);
-     vmx->nested.nested_run_pending = !ret;
-     if (ret > 0)
-             return 1;
-     else if (ret)
-             return nested_vmx_failValid(vcpu,
-                     VMXERR_ENTRY_INVALID_CONTROL_FIELD);
+     status = nested_vmx_enter_non_root_mode(vcpu, true);

What if we use a goto to bury the error handling at the end? That'd also provide some flexibility with respect to handling each failure, e.g.:

        vmx->nested.nested_run_pending = 1;
        status = nested_vmx_enter_non_root_mode(vcpu, true);
        if (status != ENTER_VMX_SUCCESS)
                goto vmenter_failed;

        ...

        return 1;

vmenter_failed:

        vmx->nested.nested_run_pending = 0;
        if (status == ENTER_VMX_VMFAIL)
                return nested_vmx_failValid(vcpu,
                                            VMXERR_ENTRY_INVALID_CONTROL_FIELD);

        return status == ENTER_VMX_ERROR ? 0 : 1;

        vmx->nested.nested_run_pending = 1;
        status = nested_vmx_enter_non_root_mode(vcpu, true);
        if (status != ENTER_VMX_SUCCESS)
                goto vmenter_failed;

        ...

        return 1;

vmenter_failed:

Quoted 8 lines

        vmx->nested.nested_run_pending = 0;
        if (status == ENTER_VMX_ERROR)
                return 0;
        if (status == ENTER_VMX_VMEXIT)
                return 1;

        WARN_ON_ONCE(status != ENTER_VMX_VMFAIL);
        return nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);

Sounds good. Thanks!

Quoted 71 lines

arch/x86/kvm/vmx/nested.c +15 -0

+     if (status != ENTER_VMX_SUCCESS) {
+             vmx->nested.nested_run_pending = 0;
+             switch (status) {
+             case ENTER_VMX_VMFAIL:
+                     return nested_vmx_failValid(vcpu,
+                             VMXERR_ENTRY_INVALID_CONTROL_FIELD);
+             case ENTER_VMX_VMEXIT:
+                     return 1;
+             case ENTER_VMX_ERROR:
+                     return 0;
+             default:
+                     WARN_ON_ONCE(1);
+                     break;
+             }
+     }
 
      /* Hide L1D cache contents from the nested guest.  */
      vmx->vcpu.arch.l1tf_flush_l1d = true;

arch/x86/kvm/vmx/nested.h +12 -1

index 187d39bf0bf1..07cf5cef86f6 100644
@@ -6,6 +6,16 @@
 #include "vmcs12.h"
 #include "vmx.h"
 
+/*
+ * Status returned by nested_vmx_enter_non_root_mode():
+ */
+enum enter_vmx_status {
+     ENTER_VMX_SUCCESS,      /* Successfully entered VMX non-root mode */
+     ENTER_VMX_VMFAIL,       /* Consistency check VMFail */
+     ENTER_VMX_VMEXIT,       /* Consistency check VMExit */
+     ENTER_VMX_ERROR,        /* KVM internal error */
+};
+
 void vmx_leave_nested(struct kvm_vcpu *vcpu);
 void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps,
                              bool apicv);

@@ -13,7 +23,8 @@ void nested_vmx_hardware_unsetup(void);
 __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *));
 void nested_vmx_vcpu_setup(void);
 void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu);
-int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry);
+enum enter_vmx_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
+                                                  bool from_vmentry);
 bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason);
 void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
                     u32 exit_intr_info, unsigned long exit_qualification);

arch/x86/kvm/x86.c +6 -3

index f26f8be4e621..627fd7ff3a28 100644
@@ -7937,8 +7937,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
      bool req_immediate_exit = false;
 
      if (kvm_request_pending(vcpu)) {
-             if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu))
-                     kvm_x86_ops->get_vmcs12_pages(vcpu);
+             if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu)) {
+                     if (unlikely(!kvm_x86_ops->get_vmcs12_pages(vcpu))) {
+                             r = 0;
+                             goto out;
+                     }
+             }
              if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
                      kvm_mmu_unload(vcpu);
              if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))
--

2.23.0.581.g78d2f28ef7-goog

Sean Christopherson

2019-10-14 19:15 UTC #3 lore raw

Quoted 25 lines · Jim Mattson

Quoted 14 lines · Sean Christopherson

Quoted 14 lines

arch/x86/kvm/vmx/nested.c +0 -6

@@ -2947,19 +2947,18 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
                      vmx->nested.apic_access_page = NULL;
              }
              page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->apic_access_addr);
-             /*
-              * If translation failed, no matter: This feature asks
-              * to exit when accessing the given address, and if it
-              * can never be accessed, this feature won't do
-              * anything anyway.
-              */
              if (!is_error_page(page)) {
                      vmx->nested.apic_access_page = page;
                      hpa = page_to_phys(vmx->nested.apic_access_page);
                      vmcs_write64(APIC_ACCESS_ADDR, hpa);

Quoted 8 lines

arch/x86/kvm/vmx/nested.c static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu) · line 2956
Quoted 5 lines
arch/x86/kvm/vmx/nested.c +2 -2
              } else {
-                     secondary_exec_controls_clearbit(vmx,
-                             SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES);
+                     pr_debug_ratelimited("%s: non-cacheable APIC-access address in vmcs12\n",
+                                          __func__);
Hmm, "non-cacheable" is confusing, especially in the context of the APIC, which needs to be mapped "uncacheable". Maybe just "invalid"?

Quoted 4 lines

"Invalid" is not correct. L1 MMIO addresses are valid; they're just not cacheable. Perhaps:
"vmcs12 APIC-access address references a page not backed by a memslot in L1"?

Hmm, technically is_error_page() isn't limited to a non-existent memslot, any GFN that doesn't lead to a 'struct page' will trigger is_error_page().

Maybe just spit out what literally went wrong? E.g something like

pr_debug_ratelimited("%s: no backing 'struct page' for APIC-access address in vmcs12\n"

Quoted 40 lines

Quoted 32 lines

Quoted 18 lines

arch/x86/kvm/vmx/nested.c +6 -0

+                     vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+                     vcpu->run->internal.suberror =
+                             KVM_INTERNAL_ERROR_EMULATION;
+                     vcpu->run->internal.ndata = 0;
+                     return false;
              }
      }

@@ -3004,6 +3003,7 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
              exec_controls_setbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
      else
              exec_controls_clearbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
+     return true;
 }
 
 /*

@@ -3042,13 +3042,15 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 /*

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3047

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +3 -5

  * If from_vmentry is false, this is being called from state restore (either RSM
  * or KVM_SET_NESTED_STATE).  Otherwise it's called from vmlaunch/vmresume.
-+ *
-+ * Returns:
-+ *   0 - success, i.e. proceed with actual VMEnter
-+ *   1 - consistency check VMExit
-+ *  -1 - consistency check VMFail
+ *
+ * Returns:
+ *   ENTER_VMX_SUCCESS: Successfully entered VMX non-root mode

"Enter VMX" usually refers to VMXON, e.g. the title of VMXON in the SDM is "Enter VMX Operation".

Quoted 1 line

Maybe NVMX_ENTER_NON_ROOT_?

How about NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_?

Quoted 4 lines

Quoted 3 lines

arch/x86/kvm/vmx/nested.c +3 -0

+ *   ENTER_VMX_VMFAIL:  Consistency check VMFail
+ *   ENTER_VMX_VMEXIT:  Consistency check VMExit
+ *   ENTER_VMX_ERROR:   KVM internal error

Quoted 6 lines

Quoted 4 lines
Probably need to more explicit than VMX_ERROR, e.g. all of the VM-Fail defines are prefixed with VMXERR_##.
May ENTER_VMX_KVM_ERROR? (Or NVMX_ENTER_NON_ROOT_KVM_ERROR).
NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_KVM_INTERNAL_ERROR?

I can't tell if you're making fun of me for being pedantic about "Enter VMX", or if you really want to have a 57 character enum. :-)

NESTED_VMENTER_?

Jim Mattson

author

2019-10-14 19:37 UTC #4 lore raw

Quoted 30 lines · Sean Christopherson

Quoted 28 lines · Jim Mattson

Quoted 14 lines · Sean Christopherson

Quoted 14 lines

arch/x86/kvm/vmx/nested.c +0 -6

@@ -2947,19 +2947,18 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
                      vmx->nested.apic_access_page = NULL;
              }
              page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->apic_access_addr);
-             /*
-              * If translation failed, no matter: This feature asks
-              * to exit when accessing the given address, and if it
-              * can never be accessed, this feature won't do
-              * anything anyway.
-              */
              if (!is_error_page(page)) {
                      vmx->nested.apic_access_page = page;
                      hpa = page_to_phys(vmx->nested.apic_access_page);
                      vmcs_write64(APIC_ACCESS_ADDR, hpa);

Quoted 8 lines

arch/x86/kvm/vmx/nested.c static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu) · line 2956
Quoted 5 lines
arch/x86/kvm/vmx/nested.c +2 -2
              } else {
-                     secondary_exec_controls_clearbit(vmx,
-                             SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES);
+                     pr_debug_ratelimited("%s: non-cacheable APIC-access address in vmcs12\n",
+                                          __func__);
Hmm, "non-cacheable" is confusing, especially in the context of the APIC, which needs to be mapped "uncacheable". Maybe just "invalid"?

"Invalid" is not correct. L1 MMIO addresses are valid; they're just not cacheable. Perhaps:

Quoted 8 lines

Quoted 1 line
"vmcs12 APIC-access address references a page not backed by a memslot in L1"?
Hmm, technically is_error_page() isn't limited to a non-existent memslot, any GFN that doesn't lead to a 'struct page' will trigger is_error_page().
Maybe just spit out what literally went wrong? E.g something like
pr_debug_ratelimited("%s: no backing 'struct page' for APIC-access address in vmcs12\n"

Perfect!

Quoted 43 lines

Quoted 32 lines

Quoted 18 lines

arch/x86/kvm/vmx/nested.c +6 -0

+                     vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+                     vcpu->run->internal.suberror =
+                             KVM_INTERNAL_ERROR_EMULATION;
+                     vcpu->run->internal.ndata = 0;
+                     return false;
              }
      }

@@ -3004,6 +3003,7 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
              exec_controls_setbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
      else
              exec_controls_clearbit(vmx, CPU_BASED_USE_MSR_BITMAPS);
+     return true;
 }
 
 /*

@@ -3042,13 +3042,15 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 /*

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3047

Quoted 10 lines

arch/x86/kvm/vmx/nested.c +3 -5

  * If from_vmentry is false, this is being called from state restore (either RSM
  * or KVM_SET_NESTED_STATE).  Otherwise it's called from vmlaunch/vmresume.
-+ *
-+ * Returns:
-+ *   0 - success, i.e. proceed with actual VMEnter
-+ *   1 - consistency check VMExit
-+ *  -1 - consistency check VMFail
+ *
+ * Returns:
+ *   ENTER_VMX_SUCCESS: Successfully entered VMX non-root mode

"Enter VMX" usually refers to VMXON, e.g. the title of VMXON in the SDM is "Enter VMX Operation".

Quoted 1 line

Maybe NVMX_ENTER_NON_ROOT_?

How about NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_?

Quoted 7 lines

arch/x86/kvm/vmx/nested.c static void load_vmcs12_host_state(struct kvm_vcpu *vcpu, · line 3050
Quoted 3 lines
arch/x86/kvm/vmx/nested.c +3 -0
+ *   ENTER_VMX_VMFAIL:  Consistency check VMFail
+ *   ENTER_VMX_VMEXIT:  Consistency check VMExit
+ *   ENTER_VMX_ERROR:   KVM internal error
Probably need to more explicit than VMX_ERROR, e.g. all of the VM-Fail defines are prefixed with VMXERR_##.

Quoted 8 lines

Quoted 3 lines
Quoted 1 line
May ENTER_VMX_KVM_ERROR? (Or NVMX_ENTER_NON_ROOT_KVM_ERROR).
NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_KVM_INTERNAL_ERROR?
I can't tell if you're making fun of me for being pedantic about "Enter VMX", or if you really want to have a 57 character enum. :-)
NESTED_VMENTER_?

It's difficult to balance brevity and clarity. I have no problem with 57 character enums, but I understand that Linux line-wrapping conventions are designed for the VT100, so long enums present a challenge. :-)

How about:

NVMX_VMENTRY_SUCCESS
NVMX_VMENTRY_VMFAIL
NVMX_VMENTRY_VMEXIT
NVMX_VMENTRY_INTERNAL_ERROR

Sean Christopherson

2019-10-14 19:52 UTC #5 lore raw

Quoted 9 lines · Jim Mattson

Quoted 7 lines · Sean Christopherson
Quoted 1 line · Jim Mattson
NESTED_VMX_ENTER_NON_ROOT_MODE_STATUS_KVM_INTERNAL_ERROR?
I can't tell if you're making fun of me for being pedantic about "Enter VMX", or if you really want to have a 57 character enum. :-)

Quoted 6 lines

Quoted 1 line
NESTED_VMENTER_?
It's difficult to balance brevity and clarity. I have no problem with 57 character enums, but I understand that Linux line-wrapping conventions are designed for the VT100, so long enums present a challenge. :-)

Heh, the real problem is that I forgot what I was reading by the time I got to "STATUS".

Quoted 6 lines

How about:
NVMX_VMENTRY_SUCCESS
NVMX_VMENTRY_VMFAIL
NVMX_VMENTRY_VMEXIT
NVMX_VMENTRY_INTERNAL_ERROR

Works for me. Maybe NVMX_VMENTRY_KVM_INTERNAL_ERROR to be consistent?