Re: [PATCH v5 04/22] x86/virt/seamldr: Introduce a wrapper for P-SEAMLDR SEAMCALLs

[Chao Gao]

>> +/*
>> + * Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
>> + * interact with P-SEAMLDR simultaneously. Use raw version as the calls can
>> + * be made with interrupts disabled.
>
>Hm. I am not sure how it explains use of raw_spinlock. What's wrong with
>using plain spinlock with interrupts disabled?

We mustn't acquire sleeping lock with interrupts disabled. in RT kernel, a plain
spinlock becomes a sleeping lock.

The lock doc [*] states:
  On PREEMPT_RT kernels, these lock types are converted to sleeping locks:
  local_lock
  spinlock_t
  rwlock_t

*:https://docs.kernel.org/locking/locktypes.html

and also see the test I did:

  https://lore.kernel.org/kvm/abPEit+Ckeqmypv+@xxxxxxxxx/

How about:

/*
 * Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
 * interact with P-SEAMLDR simultaneously. Use raw version as the calls can
 * be made with interrupts disabled, where plain spinlocks are prohibited in
 * PREEMPT_RT kernels as they become sleeping locks.
 */