Re: [PATCH] KVM: Fix steal time asm constraints in 32-bit mode

[Paolo Bonzini]

On 11/14/21 09:59, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> 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".
>
> Fixes: 7e2175ebd695 ("KVM: x86: Fix recording of guest steal time / preempted status")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
>   arch/x86/kvm/x86.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8f156905ae38..0a689bb62e9e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3307,7 +3307,7 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
>   			     "xor %1, %1\n"
>   			     "2:\n"
>   			     _ASM_EXTABLE_UA(1b, 2b)
> -			     : "+r" (st_preempted),
> +			     : "+q" (st_preempted),
>   			       "+&r" (err)
>   			     : "m" (st->preempted));
>   		if (err)

Queued with the addition of the "m" -> "+m" change, thanks.

Paolo