[+Marc] On Tue, May 19, 2020 at 07:54:51PM +0200, Jean-Philippe Brucker wrote: > The SMMUv3 can handle invalidation targeted at TLB entries with shared > ASIDs. If the implementation supports broadcast TLB maintenance, enable it > and keep track of it in a feature bit. The SMMU will then be affected by > inner-shareable TLB invalidations from other agents. > > A major side-effect of this change is that stage-2 translation contexts > are now affected by all invalidations by VMID. VMIDs are all shared and > the only ways to prevent over-invalidation, since the stage-2 page tables > are not shared between CPU and SMMU, are to either disable BTM or allocate > different VMIDs. This patch does not address the problem. This sounds like a potential performance issue, particularly as we expose stage-2 contexts via VFIO directly. Maybe we could reserve some portion of VMID space for the SMMU? Marc, what do you reckon? Will
