From: David Woodhouse <dwmw@amazon.co.uk>
Date: Sun, 14 Nov 2021 08:59:02 +0000 (+0000)
Subject: KVM: Fix steal time asm constraints
X-Git-Tag: v5.15.73~9866
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=19e32bd1cc37c34683a214242bee7a0b114831bd;p=platform%2Fkernel%2Flinux-rpi.git

KVM: Fix steal time asm constraints

commit 964b7aa0b040bdc6ec1c543ee620cda3f8b4c68a upstream.

In 64-bit mode, x86 instruction encoding allows us to use the low 8 bits
of any GPR as an 8-bit operand. In 32-bit mode, however, we can only use
the [abcd] registers. For which, GCC has the "q" constraint instead of
the less restrictive "r".

Also fix st->preempted, which is an input/output operand rather than an
input.

Fixes: 7e2175ebd695 ("KVM: x86: Fix recording of guest steal time / preempted status")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <89bf72db1b859990355f9c40713a34e0d2d86c98.camel@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3de93d4bf16b..c48e2b5729c5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3242,9 +3242,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 			     "xor %1, %1\n"
 			     "2:\n"
 			     _ASM_EXTABLE_UA(1b, 2b)
-			     : "+r" (st_preempted),
-			       "+&r" (err)
-			     : "m" (st->preempted));
+			     : "+q" (st_preempted),
+			       "+&r" (err),
+			       "+m" (st->preempted));
 		if (err)
 			goto out;