[PATCH v12 6/7] arm64: mte: Save/Restore TFSR_EL1 during suspend
vincenzo.frascino at arm.com
Tue Feb 9 09:54:13 EST 2021
On 2/9/21 2:33 PM, Lorenzo Pieralisi wrote:
>> Do we need a similar fix for TFSRE0_EL1? We get away with this if
>> suspend is only entered on the idle (kernel) thread but I recall we
>> could also enter suspend on behalf of a user process (I may be wrong
> Yes, when we suspend the machine to RAM, we execute suspend on behalf
> on a userspace process (but that's only running on 1 cpu, the others
> are hotplugged out).
> IIUC (and that's an if) TFSRE0_EL1 is checked on kernel entry so I don't
> think there is a need to save/restore it (just reset it on suspend
> TFSR_EL1, I don't see a point in saving/restoring it (it is a bit
> per-CPU AFAICS) either, IMO we should "check" it on suspend (if it is
> possible in that context) and reset it on resume.
> I don't think though you can "check" with IRQs disabled so I suspect
> that TFSR_EL1 has to be saved/restored (which means that there is a
> black out period where we run kernel code without being able to detect
> faults but there is no solution to that other than delaying saving the
> value to just before calling into PSCI). Likewise on resume from low
Ok, based on what you are saying it seems that the most viable solution here is
to save and restore TFSR_EL1. I will update my code accordingly.
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