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

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Date:   Thu, 8 Mar 2018 15:33:58 +0200
From:   Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:     Pali Rohár <pali.rohar@...il.com>,
        Pavel Machek <pavel@....cz>
Cc:     Alex Shi <alex.shi@...aro.org>, sre@...nel.org,
        linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
        aaro.koskinen@....fi, patrikbachan@...il.com, serge@...lyn.com,
        abcloriens@...il.com, clayton@...ftyguy.net, martijn@...xit.nl,
        sakari.ailus@...ux.intel.com,
        Filip Matijević <filip.matijevic.pz@...il.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Will Deacon <will.deacon@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        stable@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/45] arm Spectre fix backport review for LTS 4.9

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