linux-kernel - Re: [PATCH] xen: fix logical error in tlb flushing

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Date:	Wed, 05 Sep 2012 13:34:52 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Jan Beulich <JBeulich@...e.com>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, tglx@...utronix.de,
	mingo@...hat.com, linux-kernel@...r.kernel.org, hpa@...or.com,
	"Ren, Yongjie" <yongjie.ren@...el.com>
Subject: Re: [PATCH] xen: fix logical error in tlb flushing

On 08/25/2012 03:45 AM, Jan Beulich wrote:

>>>> On 24.08.12 at 20:17, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:
>> On Fri, Aug 24, 2012 at 04:16:39PM +0100, Jan Beulich wrote:
>>>>>> On 24.08.12 at 10:55, Alex Shi <alex.shi@...el.com> wrote:
>>>> While TLB_FLUSH_ALL gets passed as 'end' argument to
>>>> flush_tlb_others(), the Xen code was made to check its 'start'
>>>> parameter. That may give a incorrect op.cmd to MMUEXT_INVLPG_MULTI
>>>> instead of MMUEXT_TLB_FLUSH_MULTI. Then it causes some page can not
>>>> be flushed from TLB.
>>>>
>>>> This patch fixed this issue.
>>>>
>>>> Reported-by: Jan Beulich <jbeulich@...e.com>
>>>> Signed-off-by: Alex Shi <alex.shi@...el.com>
>>>
>>> Acked-by: Jan Beulich <jbeulich@...e.com>



CC to Yongjie,
Could you like to test this patch on PV guest

>>
>> How can I reproduce this

>

> I don't know, I spotted this while looking at the code.


Again, since the old buggy code doesn't cause trouble in PV guest, guess
the hypercall for MMUEXT_INVLPG_MULTI was translated or treated as
MMUEXT_TLB_FLUSH_MULTI. If so, believe correct this will bring a big
performance benefit.


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