[PATCH 3.16 003/254] KVM: x86: Exit to user-mode on #UD intercept when emulator requires

[Ben Hutchings]

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Liran Alon <liran.a...@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.a...@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshche...@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Reviewed-by: Wanpeng Li <wanpeng...@hotmail.com>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Radim Krčmář <rkrc...@redhat.com>
Signed-off-by: Ben Hutchings <b...@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;