linux-kernel - Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <10288041-8c3d-7e3a-9049-10b9fcd8baed@acm.org>
Date:   Thu, 28 Jul 2022 13:29:24 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     "Asutosh Das (asd)" <quic_asutoshd@...cinc.com>,
        John Garry <john.garry@...wei.com>,
        Can Guo <quic_cang@...cinc.com>, stanley.chu@...iatek.com,
        adrian.hunter@...el.com, alim.akhtar@...sung.com,
        avri.altman@....com, beanhuo@...ron.com, quic_nguyenb@...cinc.com,
        quic_ziqichen@...cinc.com, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com
Cc:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Daejun Park <daejun7.park@...sung.com>,
        Jinyoung Choi <j-young.choi@...sung.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support

On 7/28/22 12:15, Asutosh Das (asd) wrote:
> Hello John,
> 
> On 7/28/2022 12:10 PM, John Garry wrote:
>> On 19/07/2022 08:01, Can Guo wrote:
>>> +
>>> +    hba->nr_queues[HCTX_TYPE_DEFAULT] = num_possible_cpus();
>>> +    hba->nr_queues[HCTX_TYPE_READ] = 0;
>>> +    hba->nr_queues[HCTX_TYPE_POLL] = 1;
>>> +
>>> +    for (i = 0; i < HCTX_MAX_TYPES; i++)
>>> +        host->nr_hw_queues += hba->nr_queues[i];
>>> +
>>> +    host->can_queue = hba->nutrs;
>>> +    host->cmd_per_lun = hba->nutrs;
>>> +
>>> +    /* One more reserved for dev_cmd_queue */
>>> +    hba->nr_hw_queues = host->nr_hw_queues + 1;
>>> +
>>
>> So this would mean that the host can accept .can_queue * .nr_hw_queues 
>> numbers of requests simultaneously - is that true?
>
> That would mean that .can_queue * .nr_hw_queues numbers of request may 
> be queued to the host.
> Please can you elaborate if you see an issue.

Hi Asutosh,

The `host_tagset` flag has been introduced by John and Hannes some time 
ago. See also commit bdb01301f3ea ("scsi: Add host and host template 
flag 'host_tagset'"). This flag supports sharing tags across hardware 
queues and could be used to support UFSHCI 4.0 controllers that do not 
support the EXT_IID feature.

In order not to complicate the implementation further, I propose to fall 
back to the UFSHCI 3.0 compatibility mode for UFSHCI 4.0 controllers 
that do not support the EXT_IID feature.

To answer John's question: the maximum number of outstanding commands is 
16 * hba->nutrs if EXT_IID is supported (EXT_IID is a four bits field). 
If the hardware queue index is encoded in the EXT_IID field, hba->nutrs 
is the number of commands per hardware queue.

Thanks,

Bart.