[129/139] KVM: VMX: Update instruction length on intercepted BP

[Greg KH]

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

(Cherry-picked from commit c573cd22939e54fc1b8e672054a505048987a7cb)

We intercept #BP while in guest debugging mode. As VM exits due to
intercepted exceptions do not necessarily come with valid
idt_vectoring, we have to update event_exit_inst_len explicitly in such
cases. At least in the absence of migration, this ensures that
re-injections of #BP will find and use the correct instruction length.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/x86/kvm/vmx.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2719,6 +2719,12 @@ static int handle_rmode_exception(struct
 		kvm_queue_exception(vcpu, vec);
 		return 1;
 	case BP_VECTOR:
+		/*
+		 * Update instruction length as we may reinject the exception
+		 * from user space while in guest debugging mode.
+		 */
+		to_vmx(vcpu)->vcpu.arch.event_exit_inst_len =
+			vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
 		if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
 			return 0;
 		/* fall through */
@@ -2841,6 +2847,13 @@ static int handle_exception(struct kvm_v
 		kvm_run->debug.arch.dr7 = vmcs_readl(GUEST_DR7);
 		/* fall through */
 	case BP_VECTOR:
+		/*
+		 * Update instruction length as we may reinject #BP from
+		 * user space while in guest debugging mode. Reading it for
+		 * #DB as well causes no harm, it is not used in that case.
+		 */
+		vmx->vcpu.arch.event_exit_inst_len =
+			vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
 		kvm_run->exit_reason = KVM_EXIT_DEBUG;
 		kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
 		kvm_run->debug.arch.exception = ex_no;


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