[PATCH v3 0/2] arm64: Allow erratum 1418040 for late CPUs

[Sai Prakash Ranjan]

On 2020-09-09 20:23, Doug Anderson wrote:
> Hi,
> 
> On Fri, Aug 21, 2020 at 11:15 AM Catalin Marinas
> <catalin.marinas at arm.com> wrote:
>> 
>> On Fri, 31 Jul 2020 18:38:22 +0100, Marc Zyngier wrote:
>> > Erratum 1418040 currently prevents a late CPU from booting if none
>> > of the early CPUs are affected by it. This is because the handling
>> > is implemented as alternatives, and we have already got rid of them
>> > by the time userspace onlines a new CPU.
>> >
>> > A solution to this is to move everything into C code, and rely on
>> > static keys instead. Once this is done, the feature can be allowed
>> > for late CPUs.
>> >
>> > [...]
>> 
>> Applied to arm64 (for-next/fixes), thanks!
>> 
>> [1/2] arm64: Move handling of erratum 1418040 into C code
>>       https://git.kernel.org/arm64/c/d49f7d7376d0
>> [2/2] arm64: Allow booting of late CPUs affected by erratum 1418040
>>       https://git.kernel.org/arm64/c/bf87bb0881d0
> 
> NOTE: patch 2 seems to have come in through a stable merge onto Chrome
> OS 5.4 and is causing a regression when resuming from suspend.  In the
> short term we've got a revert going into our tree:
> 
> https://crrev.com/c/2399101
> 
> ...but that's obviously not a long term fix.  I haven't done any
> debugging of this myself, though I can if there's nobody more
> qualified to do it and/or nobody else has time.  I'm just trying to
> make sure that the problem is reported somewhere where others might
> notice it rather than in an obscure Chrome OS tree.  ;-)
> 

The rootcause is pretty straightforward however I'm afraid the
solution isn't so but I may be mistaken, so this happens on
big.LITTLE systems with CPUs differing in erratum 1418040
which was applicable only for big cores and not little cores.
So when trying to bringup little cores during resume, there
is a conflict as below (messages snipped from the internal bug
for more visibility).

Enabling non-boot CPUs ...
CPU features: CPU1: Detected conflict for capability 35 (ARM erratum 
1418040), System: 1, CPU: 0
CPU1: will not boot
CPU1: will not boot
CPU1: failed to come online
psci: CPU1 killed (polled 0 ms)
CPU1: died during early boot
Error taking CPU1 up: -5

Thanks,
Sai

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