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

[Ivaylo Dimitrov]

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