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

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Date:	Fri, 2 Sep 2011 09:40:32 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Igor Mammedov <imammedo@...hat.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] Re: [PATCH v2] xen: x86_32: do not enable iterrupts
 when returning from exception in interrupt context

On Fri, Sep 02, 2011 at 10:18:23AM +0200, Igor Mammedov wrote:
> On 09/01/2011 06:46 PM, Jeremy Fitzhardinge wrote:
> >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
> 
> I'm new to this stuff, would you like me to re-post it?

That is OK.  I fixed it up in the git commit. Thanks for finding this one!
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