linux-kernel - Re: [PATCH v2] xen: x86_32: do not enable iterrupts when returning from exception in interrupt context

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Message-ID: <4E5FB700.1070908@goop.org>
Date:	Thu, 01 Sep 2011 09:46:56 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Igor Mammedov <imammedo@...hat.com>
CC:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	konrad.wilk@...cle.com
Subject: Re: [PATCH v2] xen: x86_32: do not enable iterrupts when returning
 from exception in interrupt context

On 09/01/2011 04:46 AM, Igor Mammedov wrote:
> If vmalloc page_fault happens inside of interrupt handler with interrupts
> disabled then on exit path from exception handler when there is no pending
> interrupts, the following code (arch/x86/xen/xen-asm_32.S:112):
>
> 	cmpw $0x0001, XEN_vcpu_info_pending(%eax)
> 	sete XEN_vcpu_info_mask(%eax)
>
> will enable interrupts even if they has been previously disabled according to
> eflags from the bounce frame (arch/x86/xen/xen-asm_32.S:99)
>
> 	testb $X86_EFLAGS_IF>>8, 8+1+ESP_OFFSET(%esp)
> 	setz XEN_vcpu_info_mask(%eax)
>
> Solution is in setting XEN_vcpu_info_mask only when it should be set
> according to
> 	cmpw $0x0001, XEN_vcpu_info_pending(%eax)
> but not clearing it if there isn't any pending events.
>
> Reproducer for bug is attached to RHBZ 707552
>
> Signed-off-by: Igor Mammedov <imammedo@...hat.com>
> Signed-off-by: Jeremy Fitzhardinge <jeremy@...p.org>

One nit, this should be acked-by or reviewed-by, not signed-off-by,
since the patch isn't passing through my hands.

    J
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