On Wed, 29 Mar 2023 06:41:07 +0100, "Veith, Simon" <sveith@xxxxxxxxx> wrote: > > Hello Marc, > > thanks again for your proposal. > > On Fri, 2023-03-24 at 14:46 +0000, Marc Zyngier wrote: > > This series aims at satisfying multiple goals: > > > > - allow a VMM to atomically restore a timer offset for a whole VM > > instead of updating the offset each time a vcpu get its counter > > written > > > > - allow a VMM to save/restore the physical timer context, something > > that we cannot do at the moment due to the lack of offsetting > > > > - provide a framework that is suitable for NV support, where we get > > both global and per timer, per vcpu offsetting, and manage > > interrupts in a less braindead way. > > > > We fix a couple of issues along the way, both from a stylistic and > > correctness perspective. This results in a new per VM KVM API that > > allows a global offset to be set at any point in time, overriding > > both > > of the timer counter writebacks. > > > > We also take this opportunity to rework the way IRQs are associated > > with timers, something that was always a bit dodgy. This relies on a > > new lock, which should disappear once Oliver's lock ordering series > > is > > merged (we can reuse the config_lock for this). > > > > This has been tested with nVHE, VHE and NV. I do not have access to > > CNTPOFF-aware HW, but Colton managed to give it a go. Note that the > > NV patches in this series are here to give a perspective on how this > > gets used. > > > > I've updated the arch_timer selftest to allow an offset to be > > provided > > from the command line, and fixed a couple of glaring issues along the > > way. > > > > Note that this is at best 6.4 material. I have a branch stashed at > > [0] > > and based on 6.3-rc3, as well as a minimal example of the use of the > > API at [3] based on kvmtool. > > > > Simon: I'd appreciate some feedback as whether this change fits your > > requirements, given that you brought this up the first place. > > The interface looks good to me. I have yet to deliver on my promise to > test your patch series with our userspace; I am on leave this week, but > I'll give your latest iteration a go next week. No worries. I'm about to post v4, which I think is pretty ripe at this stage. Do let me know when you get a chance to try it. Thanks, M. -- Without deviation from the norm, progress is not possible.
