Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider: - [Critical] drm/msm: missing leaf IOTLB invalidation in __unmap_iommu() on qcom_iommu - [High] drm/msm: bypassed iommu_sync_map() and core IOMMU API in msm_iommu_map() - [Low] drm/msm: build failure in __map_iommu() when !CONFIG_IOMMU_API --
commit e0c13e8fe949f41860b8d6b287a4884b707293a0 Author: Rob Clark <[email protected]> drm/msm: Convert iommu map/unmap to helpers This commit converts msm_iommu_map() and msm_iommu_unmap() to use the internal __do_map() and __do_unmap() helpers with callbacks that invoke iommu_domain_ops directly instead of calling iommu_map_sgtable() and iommu_unmap(). > diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c > index 5c13ad6d5a366..479e5450a4dcd 100644 > --- a/drivers/gpu/drm/msm/msm_iommu.c > +++ b/drivers/gpu/drm/msm/msm_iommu.c > @@ -731,12 +731,38 @@ static void msm_iommu_detach(struct msm_mmu *mmu) > iommu_detach_device(iommu->domain, mmu->dev); > } > > +static size_t > +__unmap_iommu(void *arg, u64 iova, size_t pgsize, size_t pgcount) > +{ > + struct iommu_domain *domain = arg; > + return domain->ops->unmap_pages(domain, iova, pgsize, pgcount, NULL); > +} > + > +static int > +__map_iommu(void *arg, phys_addr_t paddr, u64 iova, size_t pgsize, > + size_t pgcount, int prot, size_t *mapped) > +{ > + struct iommu_domain *domain = arg; > + return domain->ops->map_pages(domain, iova, paddr, pgsize, pgcount, > + prot, GFP_KERNEL, mapped); > +} [Severity: Low] Does dereferencing domain->ops in __unmap_iommu() and __map_iommu() break the build when CONFIG_IOMMU_API is disabled? In drivers/gpu/drm/msm/Kconfig, DRM_MSM depends on IOMMU_SUPPORT and selects IOMMU_IO_PGTABLE, neither of which selects CONFIG_IOMMU_API. In include/linux/iommu.h, struct iommu_domain_ops is only forward-declared when CONFIG_IOMMU_API is not enabled, so dereferencing domain->ops->unmap_pages and domain->ops->map_pages fails to compile with an incomplete type error under SOC_IMX5 or COMPILE_TEST configurations without an IOMMU driver that selects CONFIG_IOMMU_API. > + > +static void > +__flush_iommu(void *arg) > +{ > + struct iommu_domain *domain = arg; > + iommu_flush_iotlb_all(domain); > +} [Severity: Critical] As reported by Sashiko on v3 [1], does passing NULL for the gather parameter in __unmap_iommu() followed by iommu_flush_iotlb_all() in __flush_iommu() skip hardware IOTLB invalidation completely on platforms using qcom_iommu? When msm_iommu_unmap() (or the error rollback path in msm_iommu_map() -> __do_map()) calls __do_unmap(), __unmap_iommu() calls domain->ops->unmap_pages(domain, iova, pgsize, pgcount, NULL). On SoCs using drivers/iommu/arm/arm-smmu/qcom_iommu.c (such as MSM8916, MSM8953, and MSM8976 with Adreno A3xx/A4xx/A5xx and MDP5), qcom_iommu_init_domain() uses the ARM_32_LPAE_S1 page table format in drivers/iommu/io-pgtable-arm.c. In __arm_lpae_unmap(), per-page TLB invalidation via io_pgtable_tlb_add_page() -> qcom_iommu_tlb_add_page() (which writes ARM_SMMU_CB_S1_TLBIVAL) is skipped when gather is NULL: drivers/iommu/io-pgtable-arm.c:__arm_lpae_unmap() { ... if (gather && !iommu_iotlb_gather_queued(gather)) for (int j = 0; j < i; j++) io_pgtable_tlb_add_page(iop, gather, iova + j * size, size); ... } When __do_unmap() then finishes by calling __flush_iommu() -> iommu_flush_iotlb_all(domain), qcom_iommu_flush_iotlb_all() only issues a TLBSYNC barrier without invalidating the context bank by ASID: drivers/iommu/arm/arm-smmu/qcom_iommu.c:qcom_iommu_flush_iotlb_all() { ... pm_runtime_get_sync(qcom_domain->iommu->dev); qcom_iommu_tlb_sync(pgtable->cookie); pm_runtime_put_sync(qcom_domain->iommu->dev); } As a result, neither ARM_SMMU_CB_S1_TLBIVAL nor ARM_SMMU_CB_S1_TLBIASID is written during unmap, leaving stale TLB entries pointing to unmapped and freed GEM buffer pages accessible to GPU and display DMA. > + > +static const struct map_ops iommu_ops = { > + __unmap_iommu, __map_iommu, __flush_iommu > +}; > + > static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova, > struct sg_table *sgt, size_t off, size_t len, > int prot) > { > - struct msm_iommu *iommu = to_msm_iommu(mmu); > - ssize_t ret; > + struct iommu_domain *domain = to_msm_iommu(mmu)->domain; > > WARN_ON(off != 0); > > @@ -744,23 +770,18 @@ static int msm_iommu_map(struct msm_mmu *mmu, uint64_t > iova, > if (iova & BIT_ULL(48)) > iova |= GENMASK_ULL(63, 49); > > - ret = iommu_map_sgtable(iommu->domain, iova, sgt, prot); > - if (ret < 0) > - return ret; > - > - return (ret == len) ? 0 : -EINVAL; > + return __do_map(domain->pgsize_bitmap, iova, sgt, off, len, prot, > + domain, &iommu_ops); > } > > static int msm_iommu_unmap(struct msm_mmu *mmu, uint64_t iova, size_t len) > { > - struct msm_iommu *iommu = to_msm_iommu(mmu); > + struct iommu_domain *domain = to_msm_iommu(mmu)->domain; > > if (iova & BIT_ULL(48)) > iova |= GENMASK_ULL(63, 49); > > - iommu_unmap(iommu->domain, iova, len); > - > - return 0; > + return __do_unmap(domain->pgsize_bitmap, iova, len, domain, &iommu_ops); > } [Severity: High] As reported by Sashiko on v3 [2], can bypassing the core IOMMU API in msm_iommu_map() and msm_iommu_unmap() cause missing IOTLB synchronization on map as well as regressions with arm-smmu and generic_pt domains? First, replacing iommu_map_sgtable() with __do_map() -> __map_iommu() -> domain->ops->map_pages() never calls iommu_sync_map() (domain->ops->iotlb_sync_map) after mapping pages. On APQ8064/MSM8960 (drivers/iommu/msm_iommu.c, used with MDP4 and Adreno 320), msm_iommu_ops.default_domain_ops relies on .iotlb_sync_map = msm_iommu_sync_map to flush the IOTLB range via __flush_iotlb_range() after mapping and leaves .flush_iotlb_all as NULL. Second, on arm-smmu, iommu_unmap() previously used struct iommu_iotlb_gather to perform VA-targeted leaf invalidations (ARM_SMMU_CB_S1_TLBIVAL) followed by iommu_iotlb_sync(). Calling domain->ops->unmap_pages() with a NULL gather followed by iommu_flush_iotlb_all() forces a full ASID invalidation (ARM_SMMU_CB_S1_TLBIASID) on every unmap, evicting all TLB entries for active display scanout buffers and GPU mappings sharing the ASID. Third, in drivers/iommu/iommu.c (iommu_map_nosync() and __iommu_unmap()), domains converted to the generic page table library (domain->is_iommupt) use pt->ops->map_range and unmap_range and leave domain->ops->map_pages and unmap_pages as NULL, while core wrappers also handle iommu_debug_map() / iommu_debug_unmap_begin() and IOMMU tracepoints. [1] https://lore.kernel.org/r/[email protected] [2] https://lore.kernel.org/r/[email protected] -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=4
