linux-kernel - Re: [PATCH kvm-unit-tests 2/3] x86: Test rflags.rf is set upon faults

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Date:	Mon, 21 Jul 2014 14:24:50 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Nadav Amit <namit@...technion.ac.il>
CC:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, gleb@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH kvm-unit-tests 2/3] x86: Test rflags.rf is set upon faults

Il 21/07/2014 13:39, Nadav Amit ha scritto:
> @@ -176,7 +176,7 @@ unsigned exception_vector(void)
>      unsigned short vector;
>  
>      asm("mov %%gs:4, %0" : "=rm"(vector));

"rm" is wrong here, it should be "r".  If we make it "q" instead, we can
use movb.


	unsigned char vector;

	asm("movb %%gs:4, %b0" : "=q"(vector));

> -    return vector;
> +    return (u8)vector;
>  }

> 
> +bool exception_rflags_rf(void)
> +{
> +    unsigned short rf_flag;
> +
> +    asm("mov %%gs:4, %0" : "=rm"(rf_flag));
> +    return (rf_flag >> 8) & 1;
> +}
> +

Same here, use "movb %%gs:5, %b0" and an unsigned char.

Paolo
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