Patch "KVM: x86: Exit to user-mode on #UD intercept when emulator requires" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

KVM: x86: Exit to user-mode on #UD intercept when emulator requires

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-exit-to-user-mode-on-ud-intercept-when-emulator-requires.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Liran Alon <[email protected]>
Date: Sun, 5 Nov 2017 16:56:32 +0200
Subject: KVM: x86: Exit to user-mode on #UD intercept when emulator requires
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From: Liran Alon <[email protected]>

commit 61cb57c9ed631c95b54f8e9090c89d18b3695b3c upstream.

Instruction emulation after trapping a #UD exception can result in an MMIO access, for example when emulating a MOVBE on a processor that doesn't support the instruction. In this case, the #UD vmexit handler must exit to user mode, but there wasn't any code to do so. Add it for both VMX and SVM.

---
 arch/x86/kvm/svm.c |    2 ++
 arch/x86/kvm/vmx.c |    2 ++
 2 files changed, 4 insertions(+)

@@ -1696,6 +1696,8 @@ static int ud_interception(struct vcpu_s
 	int er;
 
 	er = emulate_instruction(&svm->vcpu, EMULTYPE_TRAP_UD);
+	if (er == EMULATE_USER_EXIT)
+		return 0;
 	if (er != EMULATE_DONE)
 		kvm_queue_exception(&svm->vcpu, UD_VECTOR);
 	return 1;

@@ -5267,6 +5267,8 @@ static int handle_exception(struct kvm_v
 			return 1;
 		}
 		er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
+		if (er == EMULATE_USER_EXIT)
+			return 0;
 		if (er != EMULATE_DONE)
 			kvm_queue_exception(vcpu, UD_VECTOR);
 		return 1;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/kvm-x86-exit-to-user-mode-on-ud-intercept-when-emulator-requires.patch queue-4.4/kvm-x86-pvclock-handle-first-time-write-to-pvclock-page-contains-random-junk.patch