Hi all, PCIe permits a device to ignore ATS invalidation TLPs, while processing a reset. This creates a problem visible to the OS where an ATS invalidation command will time out: e.g. an SVA domain will have no coordination with a reset event and can racily issue ATS invalidations to a resetting device.
The OS should do something to mitigate this as we do not want production systems to be reporting critical ATS failures, especially in a hypervisor environment. Broadly, OS could arrange to ignore the timeouts, block page table mutations to prevent invalidations, or disable and block ATS. The PCIe spec in sec 10.3.1 IMPLEMENTATION NOTE recommends to disable and block ATS before initiating a Function Level Reset. It also mentions that other reset methods could have the same vulnerability as well. Provide a callback from the PCI subsystem that will enclose the reset and have the iommu core temporarily change domains to group->blocking_domain, so IOMMU drivers would fence any incoming ATS queries, synchronously stop issuing new ATS invalidations, and wait for existing ATS invalidations to complete. Doing this can avoid any ATS invaliation timeouts. When a device is resetting, any new domain attachment has to be rejected, until the reset is finished, to prevent ATS activity from being activated between the two callback functions. Introduce a new pending_reset flag to reject a concurrent __iommu_attach_device/set_group_pasid(). Finally, apply these iommu_dev_reset_prepare/done() functions in the PCI reset functions. Note that this series doesn't work well for a resetting alias device or a SRIOV PF, so skip these two corner cases. There is nothing we can do for alias devices since they share the same RID. For SRIOV PF, its VFs would need to be blocked as well, and new dryrun attach_dev/set_group_pasid ops will be required to allow compatible domain to be cached concurrently. Some future followups after this series: - A pair of dryrun testing ops for attach_dev/set_dev_pasid to make sure no incompatible attempt will be given to attach_dev/set_dev_pasid(). - Stage all VFs to the blocked domain as well, if their PF is resetting. - Clean up all unlocked iommu_get_domain_for_dev() call for UAF concern. Replace with safer alternative APIs. This is on Github: https://github.com/nicolinc/iommufd/commits/iommu_dev_reset-v4 Changelog v4 * Add Reviewed-by from Baolu * [iommu] Use guard(mutex) * [iommu] Update kdocs for typos and revisings * [iommu] Skip two corner cases (alias and SRIOV) * [iommu] Rework attach_dev to pass in old domain pointer * [iommu] Reject concurrent attach_dev/set_dev_pasid for compatibility concern * [smmuv3] Drop the old_domain depedency in its release_dev callback * [pci] Add pci_reset_iommu_prepare/_done() wrappers checking ATS cap v3 https://lore.kernel.org/all/cover.1754952762.git.nicol...@nvidia.com/ * Add Reviewed-by from Jason * [iommu] Add a fast return in iommu_deferred_attach() * [iommu] Update kdocs, inline comments, and commit logs * [iommu] Use group->blocking_domain v.s. ops->blocked_domain * [iommu] Drop require_direct, iommu_group_get(), and xa_lock() * [iommu] Set the pending_reset flag after RID/PASID domain setups * [iommu] Do not bypass PASID domains when RID domain is already the blocking_domain * [iommu] Add iommu_get_domain_for_dev_locked to correctly return the blocking_domain v2 https://lore.kernel.org/all/cover.1751096303.git.nicol...@nvidia.com/ * [iommu] Update kdocs, inline comments, and commit logs * [iommu] Replace long-holding group->mutex with a pending_reset flag * [pci] Abort reset routines if iommu_dev_reset_prepare() fails * [pci] Apply the same vulnerability fix to other reset functions v1 https://lore.kernel.org/all/cover.1749494161.git.nicol...@nvidia.com/ Thanks Nicolin Nicolin Chen (7): iommu/arm-smmu-v3: Add release_domain to attach prior to release_dev() iommu: Lock group->mutex in iommu_deferred_attach() iommu: Pass in gdev to __iommu_device_set_domain iommu: Pass in old domain to attach_dev callback functions iommu: Add iommu_get_domain_for_dev_locked() helper iommu: Introduce iommu_dev_reset_prepare() and iommu_dev_reset_done() pci: Suspend iommu function prior to resetting a device drivers/pci/pci.h | 2 + include/linux/iommu.h | 16 +- drivers/iommu/amd/iommu.c | 11 +- drivers/iommu/apple-dart.c | 9 +- .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 5 +- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 66 +++-- drivers/iommu/arm/arm-smmu/arm-smmu.c | 9 +- drivers/iommu/arm/arm-smmu/qcom_iommu.c | 11 +- drivers/iommu/dma-iommu.c | 2 +- drivers/iommu/exynos-iommu.c | 6 +- drivers/iommu/fsl_pamu_domain.c | 12 +- drivers/iommu/intel/iommu.c | 10 +- drivers/iommu/intel/nested.c | 2 +- drivers/iommu/iommu.c | 256 +++++++++++++++++- drivers/iommu/iommufd/selftest.c | 2 +- drivers/iommu/ipmmu-vmsa.c | 10 +- drivers/iommu/msm_iommu.c | 8 +- drivers/iommu/mtk_iommu.c | 8 +- drivers/iommu/mtk_iommu_v1.c | 7 +- drivers/iommu/omap-iommu.c | 12 +- drivers/iommu/riscv/iommu.c | 9 +- drivers/iommu/rockchip-iommu.c | 20 +- drivers/iommu/s390-iommu.c | 9 +- drivers/iommu/sprd-iommu.c | 3 +- drivers/iommu/sun50i-iommu.c | 8 +- drivers/iommu/tegra-smmu.c | 10 +- drivers/iommu/virtio-iommu.c | 6 +- drivers/pci/pci-acpi.c | 12 +- drivers/pci/pci.c | 68 ++++- drivers/pci/quirks.c | 18 +- 30 files changed, 509 insertions(+), 118 deletions(-) -- 2.43.0
