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SubjectRe: [PATCH] arm64/io: Don't use WZR in writel
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On 11/02/2019 14:59, 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.

And even if we *were* to just try papering over the observed extent of
the issue, I'd still be inclined to confine it to arm-smmu.c where the
impact is finite and minimal - of the 4 instances of writel(0) there, 3
of them don't care what the data is (so could just reuse the base
register or similar) and the other one already has a zero in a GPR to
hand by construction.

Robin.

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