From: David Daney <ddaney@caviumnetworks.com>
To: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: David Daney <ddaney.cavm@gmail.com>, <linux-mips@linux-mips.org>,
<ralf@linux-mips.org>, David Daney <david.daney@cavium.com>,
<stable@vger.kernel.org>
Subject: Re: MIPS: Make set_pte() SMP safe.
Date: Tue, 4 Aug 2015 13:01:59 -0700 [thread overview]
Message-ID: <55C11A37.5070509@caviumnetworks.com> (raw)
In-Reply-To: <55C10F4B.2050003@imgtec.com>
On 08/04/2015 12:15 PM, Leonid Yegoshin wrote:
> David,
>
> Did you observe this in real?
Yes. It is not hypothetical.
> The function __get_vm_area_node() allocates a guard page if flag
> VM_NO_GUARD is not used and I don't see any use of it in source.
>
> In past vmap allocated a guard page even unconditionally.
It has nothing to do with guard pages per se. The problem is if a vmap
range (including guard page) ends on an even PFN. The buddy code will
clobber the PTE for PFN+1. If another vmap operation is executing in
set_pte() for the clobbered location, you can get corrupted page tables.
>
> - Leonid.
>
WARNING: multiple messages have this Message-ID (diff)
From: David Daney <ddaney@caviumnetworks.com>
To: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: David Daney <ddaney.cavm@gmail.com>,
linux-mips@linux-mips.org, ralf@linux-mips.org,
David Daney <david.daney@cavium.com>,
stable@vger.kernel.org
Subject: Re: MIPS: Make set_pte() SMP safe.
Date: Tue, 4 Aug 2015 13:01:59 -0700 [thread overview]
Message-ID: <55C11A37.5070509@caviumnetworks.com> (raw)
Message-ID: <20150804200159.8EA4Fd4a08kDhdbWuJYKMJvUUSo2PeUuXKJ8bn_SiLo@z> (raw)
In-Reply-To: <55C10F4B.2050003@imgtec.com>
On 08/04/2015 12:15 PM, Leonid Yegoshin wrote:
> David,
>
> Did you observe this in real?
Yes. It is not hypothetical.
> The function __get_vm_area_node() allocates a guard page if flag
> VM_NO_GUARD is not used and I don't see any use of it in source.
>
> In past vmap allocated a guard page even unconditionally.
It has nothing to do with guard pages per se. The problem is if a vmap
range (including guard page) ends on an even PFN. The buddy code will
clobber the PTE for PFN+1. If another vmap operation is executing in
set_pte() for the clobbered location, you can get corrupted page tables.
>
> - Leonid.
>
next prev parent reply other threads:[~2015-08-04 20:02 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-04 0:48 [PATCH] MIPS: Make set_pte() SMP safe David Daney
2015-08-04 0:48 ` David Daney
2015-08-04 19:15 ` Leonid Yegoshin
2015-08-04 19:15 ` Leonid Yegoshin
2015-08-04 20:01 ` David Daney [this message]
2015-08-04 20:01 ` David Daney
2015-08-04 20:32 ` Leonid Yegoshin
2015-08-04 20:32 ` Leonid Yegoshin
2015-08-04 20:36 ` Leonid Yegoshin
2015-08-04 20:36 ` Leonid Yegoshin
2015-08-04 20:38 ` David Daney
2015-08-04 20:38 ` David Daney
2015-08-04 20:47 ` Leonid Yegoshin
2015-08-04 20:47 ` Leonid Yegoshin
2015-08-04 20:48 ` David Daney
2015-08-04 20:48 ` David Daney
2015-08-04 20:58 ` Leonid Yegoshin
2015-08-04 20:58 ` Leonid Yegoshin
2015-08-24 3:28 ` [PATCH] " Joshua Kinard
-- strict thread matches above, loose matches on Subject: below --
2015-08-04 0:48 David Daney
2015-08-04 0:48 David Daney
2015-08-04 0:48 David Daney
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