Re: [PATCH] KVM: arm64: Disable TRBE Trace Buffer Unit when running in guest context

[Will Deacon <will@kernel.org>]

On Wed, Feb 25, 2026 at 12:09:56PM +0000, Leo Yan wrote:
> [ + Yabin ]
> 
> Thanks for Suzuki's reminding, I should mention that Yabin reported
> another lockup issue caused by missing CPU PM support in TRBE driver.
> 
> We have a patch series to fix the issue:
> https://lore.kernel.org/linux-arm-kernel/20251119-arm_coresight_path_power_management_improvement-v5-16-f615a301ad0b@arm.com/

Two nits on that series:

1. It seems a bit weird to me for the ETE driver to manage TRFCR but for
   the TRBE driver to manage the other registers

2. Are you sure you don't need to save/restore the TRBE state when
   LIMITR.E is clear? Maybe the driver is fine with that, but I'm worried
   that we could suspend in a half-programmed state and lose some of that
   configuration.

> Besides your fix the translation regime issue, I'd also suggest applying
> the CoreSight PM patch series to fix lockup caused by CPU idle.

Yes, we definitely need something like that in the android kernel trees.
I've previously bodged a hack into the ETE PM notifiers, but if you have
backports of your series to 6.12, 6.6 and 6.1 then we should merge them
into Android. As it stands, I don't have a TRBE-capable device running
mainline.

Will