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

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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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