[PATCH v9 00/12] iommu/arm-smmu-v3: Adopt the crashed kernel's stream table for kdump

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 [*]
 - Reserve the crashed kernel's in-use ASIDs and VMIDs, preventing any TLB
   aliasing with the kdump kernel's own domains
 - Defer any default domain attachment to retain STEs until device drivers
   explicitly request it.
Most of the new code is added to two new files: arm-smmu-v3-kexec.c holds
the read-only helpers that parse and walk the crashed kernel's stream/CD
tables and reserve its in-use IDs, guarded by a hidden config symbol named
ARM_SMMU_V3_KEXEC (def_bool CRASH_DUMP); arm-smmu-v3-kdump.c then builds
the kdump adoption on top of those helpers, which are meant to be shared
with the proposed SMMUv3 Live Update support:
https://lore.kernel.org/all/[email protected]/

[*] 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 this series is no longer treated as a bug fix, since it has grown
fairly big and most of the kdump code now resides in separate files. For
folks interested in back-porting the change: a v6.12+ kernel (since commit
85196f54743d ("iommu/arm-smmu-v3: Reorganize struct arm_smmu_strtab_cfg"))
would be still compatible with this series.

This is on Github:
https://github.com/nicolinc/iommufd/commits/smmuv3_kdump-v9

Changelog
v9
 * Reject valid CD L1 descriptors carrying a null L2 pointer
 * Move the ida devres prep before the stream table adoption
 * Reject a 2-level CD table on hardware without FEAT_2_LVL_CDTAB
 * Cap the linear table log2size by sid_bits on 2-level capable HW
 * Add a hidden ARM_SMMU_V3_KEXEC config for Live Update to extend
 * Factor the table walkers and ID reservation into arm-smmu-v3-kexec.c
v8
 https://lore.kernel.org/all/[email protected]/
 * Move the kdump code into a new arm-smmu-v3-kdump.c
 * Move the EVTQ/PRIQ patches to the front of the series
 * Prefix "kdump: " to prints via dev_fmt in the new file
 * Add a prep patch destroying the vmid_map ida via devres
 * Reject valid-span L1 descriptors with a null L2 pointer
 * Document notes/limitations at the top of arm-smmu-v3-kdump.c
 * Rename arm_smmu_kdump_adopt_l2_strtab() to a deferred variant
 * Add a new patch reserving the crashed kernel's ASIDs and VMIDs
 * Make arm_smmu_get_step_for_sid() a static inline in the header
 * Validate alignments of the adopted stream table base addresses
 * Retarget to the merge window; drop the Fixes and Cc-stable tags
 * Rename the kdump probe function to arm_smmu_device_kdump_probe()
 * Document that a disabled event queue discards new events silently
 * Add a common arm_smmu_is_attach_deferred() calling a kdump helper
 * Document that acking SFM_ERR is defined but does not exit the SFM
 * Document that CR0 queue enables can be cleared while SMMUEN is set
 * Clear only the CR0 queue enables in kdump reset, keeping other fields
v7
 https://lore.kernel.org/all/[email protected]/
 * 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 (12):
  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: Add strtab parse helpers to a new
    arm-smmu-v3-kexec.c
  iommu/arm-smmu-v3: Destroy vmid_map ida via devres
  iommu/arm-smmu-v3: Add ARM_SMMU_OPT_KDUMP_ADOPT for kdump kernel
  iommu/arm-smmu-v3-kexec: Add a CD table parse helper
  iommu/arm-smmu-v3-kexec: Add ASID/VMID reservation helpers
  iommu/arm-smmu-v3-kdump: Reserve crashed kernel's ASIDs and VMIDs
  iommu/arm-smmu-v3-kdump: Implement is_attach_deferred()
  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/Kconfig                     |   4 +
 drivers/iommu/arm/arm-smmu-v3/Makefile        |   2 +
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  66 +++
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kdump.c | 288 +++++++++++
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kexec.c | 461 ++++++++++++++++++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 246 +++++++---
 6 files changed, 999 insertions(+), 68 deletions(-)
 create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kdump.c
 create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kexec.c

-- 
2.43.0