From mboxrd@z Thu Jan  1 00:00:00 1970
From: Corneliu ZUZU <czuzu@bitdefender.com>
Subject: Re: [PATCH V2] arm: p2m.c bug-fix: hypervisor hang on
 __p2m_get_mem_access
Date: Wed, 3 Feb 2016 13:54:54 +0200
Message-ID: <56B1EA8E.3070100@bitdefender.com>
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To: Ian Campbell <ian.campbell@citrix.com>, xen-devel@lists.xen.org
Cc: Stefano Stabellini <stefano.stabellini@citrix.com>
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On 2/3/2016 1:48 PM, Ian Campbell wrote:
> On Wed, 2016-01-27 at 14:24 +0200, Corneliu ZUZU wrote:
>> When __p2m_get_mem_access gets called, the p2m lock is already taken
>> by either get_page_from_gva or p2m_get_mem_access.
>>
>> Possible code paths:
>> 1)	-> get_page_from_gva
>> 		-> p2m_mem_access_check_and_get_page
>> 			-> __p2m_get_mem_access
>> 2)	-> p2m_get_mem_access
>> 		-> __p2m_get_mem_access
>>
>> In both cases if __p2m_get_mem_access subsequently gets to
>> call p2m_lookup (happens if !radix_tree_lookup(...)), a hypervisor
>> hang will occur, since p2m_lookup also spin-locks on the p2m lock.
>>
>> This bug-fix simply replaces the p2m_lookup call from
>> __p2m_get_mem_access
>> with a call to __p2m_lookup.
>>
>> Following Ian's suggestion, we also add an ASSERT to ensure that
>> the p2m lock is taken upon __p2m_get_mem_access entry.
>>
>> Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
> Acked + applied, thanks.
>
>
I thought this mail was not sent properly (didn't find it any longer on 
the web (?)) and I resent it just earlier.
I figured it must've been the fact that I forgot to put a "Changed since 
v1" section & that I didn't include an
"--in-reply-to" option. Apparently it was actually sent correctly.
Sorry, ignore the last one (which contains a "Changed since v1" section).

Corneliu.