From a9c7399d6cda0a092b347f8ee49bbe44f6e1fe66 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@redhat.com>
Date: Wed, 4 Nov 2009 11:54:59 +0200
Subject: [PATCH] KVM: Allow internal errors reported to userspace to carry
 extra data

Usually userspace will freeze the guest so we can inspect it, but some
internal state is not available.  Add extra data to internal error
reporting so we can expose it to the debugger.  Extra data is specific
to the suberror.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 arch/x86/kvm/mmu.c  | 1 +
 arch/x86/kvm/vmx.c  | 1 +
 include/linux/kvm.h | 4 ++++
 virt/kvm/kvm_main.c | 1 +
 4 files changed, 7 insertions(+)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a9024797b21..4c3e5b2314c 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2800,6 +2800,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code)
 	case EMULATE_FAIL:
 		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 		vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+		vcpu->run->internal.ndata = 0;
 		return 0;
 	default:
 		BUG();
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c9cc9596e1a..c0e66dd58a4 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3352,6 +3352,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 			kvm_report_emulation_failure(vcpu, "emulation failure");
 			vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 			vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+			vcpu->run->internal.ndata = 0;
 			ret = 0;
 			goto out;
 		}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index ca62b8e056f..172639e9439 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -251,6 +251,9 @@ struct kvm_run {
 		} dcr;
 		struct {
 			__u32 suberror;
+			/* Available with KVM_CAP_INTERNAL_ERROR_DATA: */
+			__u32 ndata;
+			__u64 data[16];
 		} internal;
 		/* Fix the size of the union. */
 		char padding[256];
@@ -484,6 +487,7 @@ struct kvm_ioeventfd {
 #define KVM_CAP_XEN_HVM 38
 #endif
 #define KVM_CAP_ADJUST_CLOCK 39
+#define KVM_CAP_INTERNAL_ERROR_DATA 40
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bd44fb48ac4..f92ba138007 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1653,6 +1653,7 @@ static long kvm_dev_ioctl_check_extension_generic(long arg)
 #ifdef CONFIG_KVM_APIC_ARCHITECTURE
 	case KVM_CAP_SET_BOOT_CPU_ID:
 #endif
+	case KVM_CAP_INTERNAL_ERROR_DATA:
 		return 1;
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
 	case KVM_CAP_IRQ_ROUTING: