linux-kernel - Re: [PATCH] iommu: Avoid softlockup and rcu stall in fq_flush

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] [day] [month] [year] [list]

Message-ID: <57017dea-c453-82bc-18b1-79663e77552d@oracle.com>
Date:   Mon, 22 May 2023 16:35:34 +0100
From:   John Garry <john.g.garry@...cle.com>
To:     Jerry Snitselaar <jsnitsel@...hat.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     Vasant Hegde <vasant.hegde@....com>,
        Peng Zhang <zhangpeng.00@...edance.com>,
        Robin Murphy <robin.murphy@....com>, will@...nel.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Li Bin <huawei.libin@...wei.com>,
        Xie XiuQi <xiexiuqi@...wei.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: Re: [PATCH] iommu: Avoid softlockup and rcu stall in
 fq_flush_timeout().

On 22/05/2023 16:18, Jerry Snitselaar wrote:
>> My guess is that the allocations are too big and not covered by the
>> allocation sizes supported by the flush-queue code. But maybe this is
>> something that can be fixed. Or the flush-queue code could even be
>> changed to auto-adapt to allocation patterns of the device driver?
>>
>> Regards,
>>
>> 	Joerg
> In the case I know of it involved some proprietary test suites
> (Hazard I/O, and Medusa?), and the lpfc driver. I was able to force
> the condition using fio with a number of jobs running. I'll play
> around and see if I can figure out a point where it starts to become
> an issue.
> 
> I mentioned what the nvme driver did to the Broadcom folks for the max
> dma size, but I haven't had a chance to go looking at it myself yet to
> see if there is somewhere in the lpfc code to fix up.

JFYI, SCSI core already supports setting this in shost->opt_sectors, see 
example in sas_host_setup().

This issue may continue to pop up so we may need a better way to turn it 
on/off for all drivers or classes of drivers.

John