Re: [PATCH] scsi: ufs: core: Avoid unsafe MMIO reads in ufshcd_mcq_compl_all_cqes_lock()

[Bart Van Assche <bvanassche@acm.org>]

On 9/1/26 5:23 AM, Stanley Jhu wrote:
> Reading host controller registers (such as CQTP) is unsafe when the
> host controller is disabled (HCE = 0), as accessing registers in an
> unclocked or reset state can cause bus stalls and system hangs.
> 
> In ufshcd_mcq_compl_all_cqes_lock(), all completion queue entries have
> already been inspected, processed, and cleared in memory, so the
> software queue is logically empty.
> 
> Avoid the unsafe MMIO read of CQTP by synchronizing hwq->cq_tail_slot
> directly to hwq->cq_head_slot in software. Upon subsequent controller
> re-initialization, ufshcd_mcq_make_queues_operational() will
> reconfigure and re-zero all queue pointers.
ufshcd_mcq_compl_all_cqes_lock() is only used to forcibly complete UFS
commands. The UFS driver should not forcibly complete UFS commands from
inside its error handler. Please remove the
ufshcd_mcq_compl_all_cqes_lock() function.

Thanks,

Bart.