linux-kernel - Re: vfio/pci

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-next>] [day] [month] [year] [list]

Message-ID: <20220805160545.GA1020364@bhelgaas>
Date:   Fri, 5 Aug 2022 11:05:45 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Arinzon, David" <darinzon@...zon.com>
Cc:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "Dagan, Noam" <ndagan@...zon.com>,
        "Agroskin, Shay" <shayagr@...zon.com>,
        "Brandes, Shai" <shaibran@...zon.com>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "mk@...ihalf.com" <mk@...ihalf.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: vfio/pci - uAPI for WC

[+cc Alex, Cornelia, kvm, lkml (from "get_maintainer.pl drivers/vfio")
and rewrapped for plain-text readability]
On Thu, Aug 04, 2022 at 09:47:36AM +0000, Arinzon, David wrote:
> Hi,
> 
> There's currently no mechanism for vfio that exposes WC-related
> operations (check if memory is WC capable, ask to WC memory) to user
> space module entities, such as DPDK, for example.
>
> This topic has been previously discussed in [1], [2] and [3], but
> there was no follow-up.
>
> This capability is very useful for DPDK, specifically to the DPDK
> ENA driver that uses vfio-pci, which requires memory to be WC on the
> TX path. Without WC, higher CPU utilization and performance
> degradation are observed.
>
> In the above mentioned discussions, three options were suggested:
> sysfs, ioctl, mmap extension (extra attributes).
> 
> Was there any progress on this area? Is there someone who's looking
> into this?
>
> We're leaning towards the ioctl option, if there are no objections,
> we'd come up with an RFC.

> [1]: https://patchwork.kernel.org/project/kvm/patch/20171009025000.39435-1-aik@ozlabs.ru/
> [2]: https://lore.kernel.org/linux-pci/2b539df4c9ec703458e46da2fc879ee3b310b31c.camel@kernel.crashing.org/
> [3]: https://lore.kernel.org/lkml/20210429162906.32742-2-sdonthineni@nvidia.com/
> 
> Thanks,
> David