Re: [PATCH v2 1/2] scsi: ufs: mcq: Fix the incorrect OCS value for the device command

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

On 6/9/23 19:15, Po-Wen Kao wrote:
> From: Stanley Chu <stanley.chu@mediatek.com>
> 
> In MCQ mode, when a device command uses a hardware queue shared
> with other commands, a race condition may occur in the following scenario:
> 
> 1. A device command is completed in CQx with CQE entry "e".
> 2. The interrupt handler copies the "cqe" pointer to "hba->dev_cmd.cqe"
>     and completes "hba->dev_cmd.complete".
> 3. The "ufshcd_wait_for_dev_cmd()" function is awakened and retrieves
>     the OCS value from "hba->dev_cmd.cqe".
> 
> However, there is a possibility that the CQE entry "e" will be overwritten
> by newly completed commands in CQx, resulting in an incorrect OCS value
> being received by "ufshcd_wait_for_dev_cmd()".
> 
> To avoid this race condition, the OCS value should be immediately copied
> to the struct "lrb" of the device command. Then "ufshcd_wait_for_dev_cmd()"
> can retrieve the OCS value from the struct "lrb".

Since with this patch applied ufs_dev_cmd.cqe is always NULL, please 
remove the 'cqe' member from struct ufs_dev_cmd.

Thanks,

Bart.