linux-kernel - [PATCH 3.16 004/254] KVM: x86: emulator: Return to user-mode on L1 CPL=0 emulation failure

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Message-ID: <lsq.1519831218.717927981@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Radim Krčmář" <rkrcmar@...hat.com>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
        "Liran Alon" <liran.alon@...cle.com>,
        "Nikita Leshenko" <nikita.leshchenko@...cle.com>,
        "Wanpeng Li" <wanpeng.li@...mail.com>
Subject: [PATCH 3.16 004/254] KVM: x86: emulator: Return to user-mode on
 L1 CPL=0 emulation failure

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

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

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

commit 1f4dcb3b213235e642088709a1c54964d23365e9 upstream.

On this case, handle_emulation_failure() fills kvm_run with
internal-error information which it expects to be delivered
to user-mode for further processing.
However, the code reports a wrong return-value which makes KVM to never
return to user-mode on this scenario.

Fixes: 6d77dbfc88e3 ("KVM: inject #UD if instruction emulation fails and exit to
userspace")

Signed-off-by: Liran Alon <liran.alon@...cle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@...cle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Reviewed-by: Wanpeng Li <wanpeng.li@...mail.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5009,7 +5009,7 @@ static int handle_emulation_failure(stru
 		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 		vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
 		vcpu->run->internal.ndata = 0;
-		r = EMULATE_FAIL;
+		r = EMULATE_USER_EXIT;
 	}
 	kvm_queue_exception(vcpu, UD_VECTOR);