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 3de93d4bf16ba737c49da3066e5ae4623c23f977..c48e2b5729c5d0ba37837ea4e2e678d19fdc7df2 100644 (file)
--- 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;