linux-kernel - Re: [PATCH v4 1/6] RDMA/bnxt_re: Eliminate duplicate barriers on weakly-ordered archs

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: <20180320152359.GL19744@ziepe.ca>
Date:   Tue, 20 Mar 2018 09:23:59 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     linux-rdma@...r.kernel.org, timur@...eaurora.org,
        sulrich@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Selvin Xavier <selvin.xavier@...adcom.com>,
        Devesh Sharma <devesh.sharma@...adcom.com>,
        Somnath Kotur <somnath.kotur@...adcom.com>,
        Sriharsha Basavapatna <sriharsha.basavapatna@...adcom.com>,
        Doug Ledford <dledford@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/6] RDMA/bnxt_re: Eliminate duplicate barriers on
 weakly-ordered archs

On Tue, Mar 20, 2018 at 10:08:16AM -0500, Sinan Kaya wrote:

> Never mind, it will break some architectures. I'll only change the first one.
> 
>  (1) On some systems, I/O stores are not strongly ordered across all CPUs, and
>      so for _all_ general drivers locks should be used and mmiowb() must be
>      issued prior to unlocking the critical section.

I think the kernel could do well to have a spin_unlock_mmiowb()
function. We have this patern quite a bit.

Arches like x86 can just make it == spin_unlock, while PPC and ARM can
add their extra barriers.

Then we can safely and efficiently use _realxed within such a
spinlock region.

Jason