Re: [PATCH v4.4 00/45] V4.4 backport of arm64 Spectre patches

[Viresh Kumar <viresh.kumar@linaro.org>]

On 17-06-19, 17:03, Julien Thierry wrote:
> On 14/06/2019 04:07, Viresh Kumar wrote:
> > Hello,
> > 
> > Here is an attempt to backport arm64 spectre patches to v4.4 stable
> > tree.
> > 
> > I have started this backport with Mark Rutland's backport of Spectre to
> > 4.9 [1] and tried applying the upstream version of them over 4.4 and
> > resolved conflicts by checking how they have been resolved in 4.9.
> > 
> > I had to pick few extra upstream patches to avoid unnecessary conflicts
> > (upstream commit ids mentioned):
> > 
> >   a842789837c0 arm64: remove duplicate macro __KERNEL__ check
> 
> I'm a bit unfamiliar with what gets or doesn't get backported. My
> understanding is that we try to backport only what's necessary to reduce
> the noise and potential introduction of issues in stable releases.
> 
> This commit is just a cleanup and (while valid) doesn't really seem
> necessary (and potential conflicts from its absence would easily be
> resolved IMO). So I'm just concerned that this doesn't constitute a
> candidate for back porting (someone can correct me if I'm wrong).

Dropped now.

> >   64f8ebaf115b mm/kasan: add API to check memory regions
> >   bffe1baff5d5 arm64: kasan: instrument user memory access API
> >   92406f0cc9e3 arm64: cpufeature: Add scope for capability check
> >   9eb8a2cdf65c arm64: cputype info for Broadcom Vulcan
> >   0d90718871fe arm64: cputype: Add MIDR values for Cavium ThunderX2 CPUs
> >   98dd64f34f47 ARM: 8478/2: arm/arm64: add arm-smccc
> > 
> > 
> > I had to drop few patches as well as they weren't getting applied
> > properly due to missing files/features (upstream commit id mentioned):
> > 
> >   93f339ef4175 arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early
> >   3c31fa5a06b4 arm64: Run enable method for errata work arounds on late CPUs
> 
> Looking at this and at the patches that implement the BP callbacks, we
> need that patch or an equivalent, otherwise we won't be using the
> correct vectors for late CPUs...
> 
> I appreciate the code has changed, but it might be worth considering
> 6a6efbb45b7d95c84840010095367eb06a64f342 as a needed dependency for BP
> hardening.

Okay, I had to pick two more patches for a clean rebase.

d4a7e845dab5 arm64: Introduce cpu_die_early
7242dbf2e4da arm64: Move cpu_die_early to smp.c
545fe20330c3 arm64: Verify CPU errata work arounds on hotplugged CPU
0365babc6c1f arm64: Run enable method for errata work arounds on late CPUs

(You can fetch my tree again to get these commit ids)

> >   6840bdd73d07 arm64: KVM: Use per-CPU vector when BP hardening is enabled
> 
> I don't believe we can do without this patch. Otherwise we're only using
> the vector that has no mitigation for kvm guests.
> 
> In v4.4, it looks like the contents of virt/kvm/arm/arm.c were contained
> in arch/arm/kvm/arm.c (yes, even for amr64). Are there other reasons
> this patch was not applying?

It was something other than this I believe, I have already used these paths for
many other patches.

Anyway, KVM stuff is mostly dropped now, just that I had to keep the changes to
arm-smccc.h from those patches.

I have updated the stable/v4.4.y/spectre branch with all the changes you
suggested and pushed the earlier version to stable/v4.4.y/spectre-v1 branch.

Will it be possible for you to have a look at stable/v4.4.y/spectre branch to
see if it is okay, so I can send the v2 version ? Don't want to spam list
unnecessary with so many patches :)

Thanks for your help Julien, really appreciate it.

-- 
viresh

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