Re: [PATCH 00/45] arm Spectre fix backport review for LTS 4.9

From: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
To: "Pali Rohár" <pali.rohar@gmail.com>, "Pavel Machek" <pavel@ucw.cz>
Cc: abcloriens@gmail.com, aaro.koskinen@iki.fi, tony@atomide.com,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	khilman@kernel.org, "Will Deacon" <will.deacon@arm.com>,
	sre@kernel.org, stable@vger.kernel.org,
	linux-kernel@vger.kernel.org, martijn@brixit.nl,
	"Filip Matijević" <filip.matijevic.pz@gmail.com>,
	clayton@craftyguy.net, sakari.ailus@linux.intel.com,
	"Marc Zyngier" <marc.zyngier@arm.com>,
	"Alex Shi" <alex.shi@linaro.org>,
	linux-omap@vger.kernel.org,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	patrikbachan@gmail.com, linux-arm-kernel@lists.infradead.org,
	serge@hallyn.com
Subject: Re: [PATCH 00/45] arm Spectre fix backport review for LTS 4.9
Date: Thu, 8 Mar 2018 15:33:58 +0200	[thread overview]
Message-ID: <36c7b85a-dadb-6e05-6c19-58c6ff6ae728@gmail.com> (raw)
In-Reply-To: <20180308132139.apabmgw4magrp3d7@pali>

Hi,

On  8.03.2018 15:21, Pali Rohár wrote:
> On Thursday 08 March 2018 13:27:15 Pavel Machek wrote:
>> Hi!
>>
>>> Resent without non-upstream patches.
>>>
>>> This backport patchset fixed the spectre issue, it's original branch:
>>> https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=kpti
>>> A few dependency or fixingpatches are also picked up, if they are necessary
>>>   and no functional changes.
>>>
>>> No bug found from kernelci.org and lkft testing. It also could be gotten from:
>>>
>>> git://git.linaro.org/kernel/linux-linaro-stable.git v4.9-spectre-upstream-only
>>>
>>> Comments are appreciated!
>>
>> Not entirely related to this patched, but... I have few older ARM
>> boards here, and Nokia N9000 I really care about.
>>
>> AFAICT Meltdown is arm64 only?
> 
> IIRC ARMv7 is not affected by meltdown.
> 
>> Spectre affects the older boards, too, right? Was there any work done
>> on that? cpuinfo says "ARMv7" for N900.
> 
> I remember that I saw some spectre patches for ARMv7 on LKML.
> 
> In general for ARMv7 it is problematic as mitigation needs to change IBE
> bit which is not possible on OMAP HS devices. But for Nokia N900 there
> is special code which do it via smc instruction (function
> rx51_secure_update_aux_cr(), see also nokia_n900_legacy_init()).
> 

I *think* N900 should be safe from spectre attack as a side effect of 
thumb2 errata (430973) workaround (BTB is flushed on every context 
switch), but don't quote me on that one, lets more knowledgeable than me 
to confirm first.

Ivo

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