iommu/arm-smmu-v3: Fix device crash on kdump kernel

When transitioning to a kdump kernel, the primary kernel might have crashed while endpoint devices were actively bus-mastering DMA. Currently, the SMMU driver aggressively resets the hardware during probe by clearing CR0_SMMUEN and setting the Global Bypass Attribute (GBPA) to ABORT.

In a kdump scenario, this aggressive reset is highly destructive:
a) If GBPA is set to ABORT, in-flight DMA will be aborted, generating fatal PCIe AER or SErrors that may panic the kdump kernel
b) If GBPA is set to BYPASS, in-flight DMA targeting some IOVAs will bypass the SMMU and corrupt the physical memory at those 1:1 mapped IOVAs.

To safely absorb in-flight DMA, the kdump kernel must leave SMMUEN=1 intact and avoid modifying STRTAB_BASE. This allows HW to continue translating in- flight DMA using the crashed kernel's page tables until the endpoint device drivers probe and quiesce their respective hardware.

However, the ARM SMMUv3 architecture specification states that updating the SMMU_STRTAB_BASE register while SMMUEN == 1 is UNPREDICTABLE or ignored.

This leaves a kdump kernel no choice but to adopt the stream table from the crashed kernel.

In this series:
- Introduce an ARM_SMMU_OPT_KDUMP_ADOPT
- Skip SMMUEN and STRTAB_BASE resets in arm_smmu_device_reset()
- Skip EVENTQ/PRIQ setup including interrupts and their handlers
- Memremap the crashed kernel's stream tables into the kdump kernel [*]
- Defer any default domain attachment to retain STEs until device drivers explicitly request it.

[*] For verification reasons, this series only fixes coherent SMMUs.

For non-ARM_SMMU_OPT_KDUMP_ADOPT cases, keep a status quo since the commit 3f54c447df34f ("iommu/arm-smmu-v3: Don't disable SMMU in kdump kernel"):
full reset followed by driver-initiated reattach, potentially rejecting any in-flight DMA.

Note that the series requires Jason's work that was merged in v6.12: commit 85196f54743d ("iommu/arm-smmu-v3: Reorganize struct arm_smmu_strtab_cfg"). I have a backported version that is verified with a v6.8 kernel. I can send if we see a strong need after this version is accepted.

This is on Github:
https://github.com/nicolinc/iommufd/commits/smmuv3_kdump-v7

Changelog
v7
* Rebase v7.2-rc1
* Add Reviewed-by from Pranjal
* Reword the linear stream table adoption comment
* Use dev_dbg for the stream table adoption message
* Document why the lazy L2 adoption uses devm_memremap()
* Drop redundant FEAT_COHERENCY checks in the adopt functions
* Use feature bit instead of STRTAB_BASE_CFG in adopt cleanup
* Skip CR0_ATSCHK update in adopt mode to retain the crashed policy
* Restore FEAT_2_LVL_STRTAB if the cleanup action fails to register
v6
https://lore.kernel.org/all/[email protected]/
* Rebase v7.1-rc3
* Add Reviewed-by from Jason
* Replace dma_addr_t with phys_addr_t
* Drop arm_smmu_kdump_phys_is_corrupted()
* Skip threaded IRQ handlers for EVTQ and PRIQ
* Bypass arm_smmu_rmr_install_bypass_ste() in kdump case
* Drop devm_ for adopt-time allocations; set up cleanup function via devm_add_action_or_reset()
v5
https://lore.kernel.org/all/[email protected]/
* Add Reviewed-by from Kevin
* Drop READ_ONCE on lazy-attach L1 read
* Split "Skip EVTQ/PRIQ setup" into two patches
* Tighten kdump probe comment and dev_warn message
* Use MEM + BUSY in arm_smmu_kdump_phys_is_corrupted
v4
https://lore.kernel.org/all/[email protected]/
* Rebase v7.1-rc1
* s/arm_smmu_adopt/arm_smmu_kdump_adopt
* Revert alloc/memremap/fmt on fallback
* Reorder patches to avoid bisect regression
* Use IRQ_NONE for spurious evtq/priq entries
* Cap linear log2size by kdump's allocation bound
* Defer clearing FEAT_2_LVL_STRTAB on linear adopt
* Add arm_smmu_kdump_phys_is_corrupted() validation
* Defer l2 stream table memremap till master inserts
* Re-validate L1 desc on master insert with READ_ONCE
v3
https://lore.kernel.org/all/[email protected]/
* s/OPT_KDUMP/OPT_KDUMP_ADOPT
* Do not adopt if GERROR_SFM_ERR
* Retain CR0_ATSCHK beside CR0_SMMUEN
* Clear latched GERROR bits (e.g. CMDQ_ERR)
* Assert ARM_SMMU_FEAT_COHERENCY in adopt functions
* Add STE.Cfg check in arm_smmu_is_attach_deferred()
* Fix validations on return codes from devm_memremap()
* Sanitize crashed kernel register values in adopt functions
* Drop unnecessary l2ptrs guard in arm_smmu_is_attach_deferred()
* Don't enable PRIQ/EVTQ irqs and guard the irq functions for combined irq cases
v2
https://lore.kernel.org/all/[email protected]/
* Add warning in non-coherent SMMU cases
* Keep eventq/priq disabled vs. enabling-and-disabling-later
* Check KDUMP option in the beginning of arm_smmu_device_reset()
* Validate STRTAB format matches HW capability instead of forcing flags
v1:
https://lore.kernel.org/all/[email protected]/

Nicolin Chen (7):
iommu/arm-smmu-v3: Add arm_smmu_kdump_adopt_strtab() for kdump iommu/arm-smmu-v3: Implement is_attach_deferred() for kdump iommu/arm-smmu-v3: Do not enable EVTQ/PRIQ interrupts in kdump kernel iommu/arm-smmu-v3: Skip EVTQ/PRIQ setup in kdump kernel iommu/arm-smmu-v3: Retain CR0_SMMUEN during kdump device reset iommu/arm-smmu-v3: Skip RMR bypass for kdump adoption iommu/arm-smmu-v3: Detect ARM_SMMU_OPT_KDUMP_ADOPT in probe()

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |   1 +
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 467 ++++++++++++++++++--
 2 files changed, 422 insertions(+), 46 deletions(-)

2.43.0