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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Paolo Bonzini" <pbonzini@redhat.com>,
        "Wanpeng Li" <wanpeng.li@hotmail.com>,
        "Liran Alon" <liran.alon@oracle.com>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
        "Nikita Leshenko" <nikita.leshchenko@oracle.com>,
        "Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?=" <rkrcmar@redhat.com>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
Message-ID: <lsq.1519831218.504012612@decadent.org.uk>
Subject: [PATCH 3.16 003/254] KVM: x86: Exit to user-mode on #UD intercept
 when emulator requires
In-Reply-To: <lsq.1519831217.271785318@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Liran Alon <liran.alon@oracle.com>

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.

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 arch/x86/kvm/svm.c | 2 ++
 arch/x86/kvm/vmx.c | 2 ++
 2 files changed, 4 insertions(+)

--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1776,6 +1776,8 @@ 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;
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4853,6 +4853,8 @@ static int handle_exception(struct kvm_v
 
 	if (is_invalid_opcode(intr_info)) {
 		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;