[PATCH v3 0/5] platform/x86/amd/hsmp: ACPI/platform HSMP concurrency and lifecycle hardening

[Muralidhara M K <muralidhara.mk@amd.com>]

This series hardens the AMD HSMP ACPI and platform drivers against
probe/remove concurrency, use-after-free of the per-socket state, and
resource leaks across unbind/rebind cycles.

On multi-socket systems several ACPI platform devices are probed and
removed independently while a single /dev/hsmp and the hwmon sysfs
attributes drive a lock-free data plane.  The existing code raced the
global is_probed handshake and the one-time socket allocation, freed the
socket array from under in-flight hsmp_send_message() callers, and leaked
metric-table mappings on rebind.

It sits on top of the ACPI mailbox-parsing and data-plane readiness
cleanups (base commit ff7836fa, "Gate the data plane on a fully
initialized socket").

The patches, in order:

  1. Serialize ACPI probe/remove/init_acpi() with a dedicated mutex so the
     is_probed handshake and the one-time socket allocation cannot race.
  2. Map the metric-table DRAM explicitly with ioremap() and unmap it from
     the driver teardown paths, so the mapping is no longer pinned to a
     per-socket devres scope and the ACPI side can coordinate its release.
  3. Serialize per-socket metric-table reads with a mutex so two concurrent
     metrics_bin readers cannot have one trigger a fresh firmware fill while
     the other is mid-copy and return a torn snapshot.  The mutex is
     initialized on both the platform and ACPI probe paths in this same
     patch so no bisection point reads metrics_bin through an uninitialized
     lock.
  4. Replace the global is_probed flag with refcounted ACPI socket
     ownership (a probe-mutex-guarded counter) and run a coordinated release
     on the last unbind: deregister /dev/hsmp, unmap the metric DRAM,
     destroy the per-socket mutexes and free the socket array.  Also drop a
     stale metric-table mapping before remapping on rebind, and stop
     parenting the shared /dev/hsmp to a per-socket device.
  5. Add hsmp_sock_rwsem so the lock-free data plane (hsmp_send_message()
     and its MMIO access) is drained and kept out while a socket is torn
     down; wire both the platform and ACPI teardown paths into it, nested
     inside the ACPI probe mutex.

Testing:
  - Each patch builds individually with no new warnings; the series is
    bisectable.
  - checkpatch.pl --strict --codespell is clean on every patch.

Changes since v2:
  - Split the old "Add explicit metric DRAM mapping and per-socket mutexes"
    patch into two single-purpose patches: the ioremap()/unmap mapping
    change (patch 2) and the per-socket read-serialization mutex (patch 3).
  - Replaced the struct kref ACPI socket refcount with a simpler counter
    guarded by the existing probe mutex, and folded the coordinated
    release, the stale-metric-mapping-on-rebind fix and the /dev/hsmp
    parent fix into that one patch (patch 4).
  - Decoupled the metric-table unmap (hsmp_unmap_metric_tbls()) from the
    mutex teardown (hsmp_destroy_metric_read_locks()) so each helper does
    exactly one thing.
  - Wired the ACPI metric-read mutex init/destroy in the same patch that
    introduces the mutex, closing a bisection window where an ACPI
    metrics_bin read could lock an uninitialized mutex.
  - Reordered the series so all hsmp_sock_rwsem writers (platform and ACPI
    teardown) land together in the final patch.

v2: https://lore.kernel.org/platform-driver-x86/eb609912-1c42-6354-22e6-5ffd1f097e9f@linux.intel.com/T/#t

Muralidhara M K (5):
  platform/x86/amd/hsmp: Serialize ACPI HSMP is_probed with a probe
    mutex
  platform/x86/amd/hsmp: Map the metric table with ioremap() and unmap
    it explicitly
  platform/x86/amd/hsmp: Serialize per-socket metric table reads with a
    mutex
  platform/x86/amd/hsmp: ACPI HSMP refcounted sockets and coordinated
    release
  platform/x86/amd/hsmp: Serialize the data plane against socket
    teardown

 drivers/platform/x86/amd/hsmp/acpi.c | 130 ++++++++++++++++++++++++---
 drivers/platform/x86/amd/hsmp/hsmp.c | 118 +++++++++++++++++++++++-
 drivers/platform/x86/amd/hsmp/hsmp.h |  16 +++-
 drivers/platform/x86/amd/hsmp/plat.c |  42 ++++++++-
 4 files changed, 286 insertions(+), 20 deletions(-)


base-commit: ff7836fa850c2f815bc219f1e48f6ec8699f4ae7
-- 
2.34.1