Re: [PATCH rfcv1 5/8] iommu/arm-smmu-v3: Pre-allocate a per-master invalidation array
From: Jason Gunthorpe <jgg@nvidia.com>
Date: 2025-08-26 19:56:48
Also in:
linux-iommu, linux-patches, lkml
On Wed, Aug 13, 2025 at 06:25:36PM -0700, Nicolin Chen wrote:
quoted hunk ↗ jump to hunk
@@ -3730,6 +3731,13 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu, return -ENOMEM; master->num_streams = fwspec->num_ids; + /* Max possible num_invs: two for ASID/VMIDs and num_ats for ATC_INVs */ + master->invs = arm_smmu_invs_alloc(2 + num_ats); + if (IS_ERR(master->invs)) { + kfree(master->streams); + return PTR_ERR(master->invs); + }
This seems like a nice solution, but I would add a comment here that it is locked by the group mutex, and check if ATS is supported: /* * Scratch memory to build the per-domain invalidation list. locked by * the group_mutex. Max possible num_invs: two for ASID/VMIDs and * num_streams for ATC_INVs */ if (dev_is_pci(master->dev) && pci_ats_supported(to_pci_dev(master->dev))) master->invs = arm_smmu_invs_alloc(2 + master->num_streams); else master->invs = arm_smmu_invs_alloc(2); And probably rename it scratch_invs or something to indicate it is temporary memory. I'm not sure there is any case where fwspec->num_ids >1 && ats_supported, or at least is should be really rare. Jason