[PATCH] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is valid

[David Edmondson <david.edmondson@xxxxxxxxxx>]

When dumping the VMCS, retrieve the current guest value of EFER from
the kvm_vcpu structure if neither VM_EXIT_SAVE_IA32_EFER or
VM_ENTRY_LOAD_IA32_EFER is set, which can occur if the processor does
not support the relevant VM-exit/entry controls.

Fixes: 4eb64dce8d0a ("KVM: x86: dump VMCS on invalid entry")
Signed-off-by: David Edmondson <david.edmondson@xxxxxxxxxx>
---
 arch/x86/kvm/vmx/vmx.c | 14 +++++++++-----
 arch/x86/kvm/vmx/vmx.h |  2 +-
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index eb69fef57485..74ea4fe6f35e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5754,7 +5754,7 @@ static void vmx_dump_dtsel(char *name, uint32_t limit)
 	       vmcs_readl(limit + GUEST_GDTR_BASE - GUEST_GDTR_LIMIT));
 }
 
-void dump_vmcs(void)
+void dump_vmcs(struct kvm_vcpu *vcpu)
 {
 	u32 vmentry_ctl, vmexit_ctl;
 	u32 cpu_based_exec_ctrl, pin_based_exec_ctrl, secondary_exec_control;
@@ -5771,7 +5771,11 @@ void dump_vmcs(void)
 	cpu_based_exec_ctrl = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
 	pin_based_exec_ctrl = vmcs_read32(PIN_BASED_VM_EXEC_CONTROL);
 	cr4 = vmcs_readl(GUEST_CR4);
-	efer = vmcs_read64(GUEST_IA32_EFER);
+	if ((vmexit_ctl & VM_EXIT_SAVE_IA32_EFER) ||
+	    (vmentry_ctl & VM_ENTRY_LOAD_IA32_EFER))
+		efer = vmcs_read64(GUEST_IA32_EFER);
+	else
+		efer = vcpu->arch.efer;
 	secondary_exec_control = 0;
 	if (cpu_has_secondary_exec_ctrls())
 		secondary_exec_control = vmcs_read32(SECONDARY_VM_EXEC_CONTROL);
@@ -5955,7 +5959,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	}
 
 	if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) {
-		dump_vmcs();
+		dump_vmcs(vcpu);
 		vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 		vcpu->run->fail_entry.hardware_entry_failure_reason
 			= exit_reason;
@@ -5964,7 +5968,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	}
 
 	if (unlikely(vmx->fail)) {
-		dump_vmcs();
+		dump_vmcs(vcpu);
 		vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 		vcpu->run->fail_entry.hardware_entry_failure_reason
 			= vmcs_read32(VM_INSTRUCTION_ERROR);
@@ -6049,7 +6053,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 
 unexpected_vmexit:
 	vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason);
-	dump_vmcs();
+	dump_vmcs(vcpu);
 	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 	vcpu->run->internal.suberror =
 			KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 9d3a557949ac..f8a0ce74798e 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -489,6 +489,6 @@ static inline bool vmx_guest_state_valid(struct kvm_vcpu *vcpu)
 	return is_unrestricted_guest(vcpu) || __vmx_guest_state_valid(vcpu);
 }
 
-void dump_vmcs(void);
+void dump_vmcs(struct kvm_vcpu *vcpu);
 
 #endif /* __KVM_X86_VMX_H */
-- 
2.30.0