virt: arm-cca-guest: use migrate_disable() for attestation token requests

The RSI attestation token init and continue calls must be issued from
the same CPU. arm_cca_report_new() currently snapshots the CPU number
and uses smp_call_function_single() to issue those calls on that CPU.

With CONFIG_DEBUG_PREEMPT=y, the smp_processor_id() call used for the
snapshot triggers a debug splat [0] because it runs in preemptible
context. The snapshot does not pin the task to that CPU; it is only used
to choose the target CPU for smp_call_function_single(), which can fail
if that CPU is no longer available.

Use migrate_disable() and issue the token init and continue operations
directly, without the smp_call_function_single() callbacks. This keeps
the token request sequence on the same CPU while preserving a sleepable
context for the GFP_KERNEL allocations needed after the init call.

[0]
 BUG: using smp_processor_id() in preemptible [00000000] code: cca-workload-at/264
 caller is debug_smp_processor_id+0x20/0x30
 CPU: 0 UID: 0 PID: 264 Comm: cca-workload-at Not tainted 7.1.0-rc1-00044-g55542ab273f2 #80 PREEMPT(lazy)
 Hardware name: linux,dummy-virt (DT)
 Call trace:
  [...]
  check_preemption_disabled+0xd8/0xf8
  debug_smp_processor_id+0x20/0x30
  arm_cca_report_new+0x48/0x278
  tsm_report_read+0x154/0x1f8
  tsm_report_outblob_read+0x20/0x38
  configfs_bin_read_iter+0x118/0x208
  vfs_read+0x220/0x318
  [...]

Fixes: 7999edc484ca ("virt: arm-cca-guest: TSM_REPORT support for realms")
Signed-off-by: Kohei Enju <enju.kohei@fujitsu.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

0 files changed, 0 insertions, 0 deletions