From: Ian Campbell <ian.campbell@citrix.com>
To: Corneliu ZUZU <czuzu@bitdefender.com>, xen-devel@lists.xen.org
Cc: Stefano Stabellini <stefano.stabellini@citrix.com>
Subject: Re: [PATCH V2] arm: p2m.c bug-fix: hypervisor hang on __p2m_get_mem_access
Date: Wed, 3 Feb 2016 11:48:42 +0000 [thread overview]
Message-ID: <1454500122.25207.88.camel@citrix.com> (raw)
In-Reply-To: <1453897475-19448-1-git-send-email-czuzu@bitdefender.com>
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.
next prev parent reply other threads:[~2016-02-03 11:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-27 12:24 [PATCH V2] arm: p2m.c bug-fix: hypervisor hang on __p2m_get_mem_access Corneliu ZUZU
2016-02-03 11:48 ` Ian Campbell [this message]
2016-02-03 11:54 ` Corneliu ZUZU
2016-02-03 12:23 ` Ian Campbell
2016-02-03 12:28 ` Corneliu ZUZU
-- strict thread matches above, loose matches on Subject: below --
2016-01-26 11:46 [PATCH] " Corneliu ZUZU
2016-02-03 11:37 ` [PATCH v2] " Corneliu ZUZU
2016-02-03 11:52 ` Ian Campbell
2016-02-03 11:56 ` Corneliu ZUZU
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