linux-kernel - Re: [Xen-devel] [PATCH] x86/xen: Fix 32-bit PV guests's usage of kernel

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Message-Id: <5345739202000078000073EA@nat28.tlf.novell.com>
Date:	Wed, 09 Apr 2014 15:21:38 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<boris.ostrovsky@...cle.com>
Cc:	<david.vrabel@...rix.com>, <xen-devel@...ts.xenproject.org>,
	<konrad.wilk@...cle.com>, <srostedt@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH] x86/xen: Fix 32-bit PV guests's usage
 of kernel_stack

>>> On 09.04.14 at 16:06, <boris.ostrovsky@...cle.com> wrote:
> --- a/arch/x86/xen/xen-asm_32.S
> +++ b/arch/x86/xen/xen-asm_32.S
> @@ -88,7 +88,11 @@ ENTRY(xen_iret)
>  	 * avoid having to reload %fs
>  	 */
>  #ifdef CONFIG_SMP
> +	pushw %fs
> +	movl $(__KERNEL_PERCPU), %eax
> +	movl %eax, %fs
>  	GET_THREAD_INFO(%eax)
> +	popw %fs

I don't think it's guaranteed that this can't fault.

Jan

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