Re: [PATCH] arm64/io: Don't use WZR in writel

From: Bjorn Andersson
Date: Sat Feb 23 2019 - 13:13:26 EST

On Mon 11 Feb 06:59 PST 2019, Marc Zyngier wrote:

> On 11/02/2019 14:29, AngeloGioacchino Del Regno wrote:
> [...]
> > Also, just one more thing: yes this thing is going ARM64-wide and
> > - from my findings - it's targeting certain Qualcomm SoCs, but...
> > I'm not sure that only QC is affected by that, others may as well
> > have the same stupid bug.
> >
> At the moment, only QC SoCs seem to be affected, probably because
> everyone else has debugged their hypervisor (or most likely doesn't
> bother with shipping one).
> In all honesty, we need some information from QC here: which SoCs are
> affected, what is the exact nature of the bug, can it be triggered from
> EL0. Randomly papering over symptoms is not something I really like
> doing, and is likely to generate problems on unaffected systems.

The bug at hand is that the XZR is not deemed a valid source in the
virtualization of the SMMU registers. It was identified and fixed for
all platforms that are shipping kernels based on v4.9 or later.

As such Angelo's list of affected platforms covers the high-profile
ones. In particular MSM8996 and MSM8998 is getting pretty good support
upstream, if we can figure out a way around this issue.