Messages in this thread | | | From | Michael Shavit <> | Date | Mon, 21 Aug 2023 21:38:40 +0800 | Subject | Re: [RFC PATCH v1 3/8] iommu/arm-smmu-v3-sva: Allocate new ASID from installed_smmus |
| |
On Mon, Aug 21, 2023 at 7:54 PM Jason Gunthorpe <jgg@nvidia.com> wrote: > > On Mon, Aug 21, 2023 at 05:31:23PM +0800, Michael Shavit wrote: > > On Fri, Aug 18, 2023 at 2:38 AM Jason Gunthorpe <jgg@nvidia.com> wrote: > > > > > > On Fri, Aug 18, 2023 at 02:16:25AM +0800, Michael Shavit wrote: > > > > Pick an ASID that is within the supported range of all SMMUs that the > > > > domain is installed to. > > > > > > > > Signed-off-by: Michael Shavit <mshavit@google.com> > > > > --- > > > > > > This seems like a pretty niche scenario, maybe we should just keep a > > > global for the max ASID? > > > > > > Otherwise we need a code to change the ASID, even for non-SVA domains, > > > when the domain is installed in different devices if the current ASID > > > is over the instance max.. > > > > This RFC took the other easy way out for this problem by rejecting > > attaching a domain if its currently assigned ASID/VMID > > is out of range when attaching to a new SMMU. But I'm not sure > > which of the two options is the right trade-off. > > Especially if we move VMID to a global allocator (which I plan to add > > for v2), setting a global maximum for VMID of 256 sounds small. > > IMHO the simplest and best thing is to make both vmid and asid as > local allocators. Then alot of these problems disappear
Well that does sound like the most flexible, but IMO quite a lot more complicated.
I'll post a v2 RFC that removes the `iommu/arm-smmu-v3: Add list of installed_smmus` patch and uses a flat master list in smmu_domain as suggested by Robin, for comparison with the v1. But at a glance using a local allocator would require: 1. Keeping that patch so we can track the asid/vmid for a domain on a per smmu instance 2. Keeping a map in the smmu struct so that arm_smmu_share_asid can find any arm_smmu_installed_smmu that need to have their asid updated (on a loop over every smmu the domain in arm_smmu_mmu_notifier_get is attached to, which just at a glance looks headache inducing because of sva's piggybacking on the rid domain.)
| |