On Tue, Feb 09, 2021 at 02:33:28PM +0000, Lorenzo Pieralisi wrote: > On Tue, Feb 09, 2021 at 11:55:33AM +0000, Catalin Marinas wrote: > > On Mon, Feb 08, 2021 at 04:56:16PM +0000, Vincenzo Frascino wrote: > > > When MTE async mode is enabled TFSR_EL1 contains the accumulative > > > asynchronous tag check faults for EL1 and EL0. > > > > > > During the suspend/resume operations the firmware might perform some > > > operations that could change the state of the register resulting in > > > a spurious tag check fault report. > > > > > > Save/restore the state of the TFSR_EL1 register during the > > > suspend/resume operations to prevent this to happen. > > > > 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 > > though). > > 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 > exit).
You are right, we don't check TFSRE0_EL1 on return to user, only clear it, so no need to do anything on suspend/resume. > 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 think this should work. > 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 > power. It depends on whether kasan_report can be called with IRQs disabled. I don't see why not, so if this works I'd rather just call mte_check_async (or whatever it's called) on the suspend path and zero the register on resume (mte_suspend_exit). We avoid any saving of the state. -- Catalin