On Mon, Dec 02, 2024 at 05:21:23PM +0000, Marc Zyngier wrote: > Here's another batch of NV-related patches, this time bringing in most > of the timer support for EL2 as well as nested guests. > > The code is pretty convoluted for a bunch of reasons: > > - FEAT_NV2 breaks the timer semantics by redirecting HW controls to > memory, meaning that a guest could setup a timer and never see it > firing until the next exit > > - We go try hard to reflect the timer state in memory, but that's not > great. > > - With FEAT_ECV, we can finally correctly emulate the virtual timer, > but this emulation is pretty costly > > - As a way to make things suck less, we handle timer reads as early as > possible, and only defer writes to the normal trap handling > > - Finally, some implementations are badly broken, and require some > hand-holding, irrespective of NV support. So we try and reuse the NV > infrastructure to make them usable. This could be further optimised, > but I'm running out of patience for this sort of HW. > > What this is not implementing is support for CNTPOFF_EL2. It appears > that the architecture doesn't let you correctly emulate it, so I guess > this will be trap/emulate for the foreseeable future. > > This series is on top of v6.13-rc1, and has been tested on my usual M2 > setup, but also on a Snapdragon X1 Elite devkit. I would like to thank > Qualcomm for the free hardware with no strings (nor support) attached! This series is looking pretty good to me, but I think it'd be good to remap "EL0 timer" -> "EL1 timer" throughout this series to match the architectural term. -- Thanks, Oliver
