On Thu, 14 Dec 2023 15:22:06 +0000 Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> wrote: > On Thu, Dec 14, 2023 at 12:30:55PM +0000, Robin Murphy wrote: > > > Robin, Jean-Philippe -- do we need to make sure that the SMMU has completed > > > its TLB invalidation before issuing an ATC invalidate? My half-baked worry > > > is whether or not an ATS request could refill the ATC before the TLBI > > > has completed, therefore rendering the ATC invalidation useless. > > > > I would agree, and the spec for CMD_ATC_INV does call out a > > TLBI->sync->ATCI->sync sequence. At the moment the SVA notifier is issuing > > its own command-based TLBIs anyway so the necessary sync is implicit there, > > but if and when we get BTM support wired up properly it would be nice not to > > have to bodge in an additional sync/DSB. > > Yes agreed, with BTM the CPU must call the notifier that issues ATC > invalidation after completing the TLBI+DSB instructions. > > SMMU IHI0070F.a 3.9.1 ATS Interface > > Software must ensure that the SMMU TLB invalidation is complete before > initiating the ATC invalidation. > > I'm guessing BTM will be enabled in the SMMU driver sometime soon, given > that there already is one implementation in the wild that could use it. I > think we didn't enable it because of the lack of separation between shared > and private VMIDs, but that may now be solvable with the recent rework of > the VMID allocator. > +CC Shameer. We'll indeed need to fix this when enabling BTM. Thanks for the heads up. Jonathan > Thanks, > Jean >
