linux-kernel - Re: [RFC] /dev/ioasid uAPI proposal

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: <20210608125201.GC1002214@nvidia.com>
Date:   Tue, 8 Jun 2021 09:52:01 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
Cc:     Jason Wang <jasowang@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Robin Murphy <robin.murphy@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Kirti Wankhede <kwankhede@...dia.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Gerd Hoffmann <kraxel@...hat.com>
Subject: Re: [RFC] /dev/ioasid uAPI proposal

On Tue, Jun 08, 2021 at 10:54:59AM +0200, Enrico Weigelt, metux IT consult wrote:

> Maybe the device as well as the transport could announce their
> capability (which IMHO should go via the virtio protocol), and if both
> are capable, the (guest's) virtio subsys tells the driver whether it's
> usable for a specific device. Perhaps we should also have a mechanism
> to tell the device that it's actually used.

The usage should be extremely narrow, like 

"If the driver issues a GPU command with flag X then the resulting
DMAs will be no-snoop and the driver must re-establish coherency at
the right moment"

It is not a general idea, but something baked directly into the device
protocol that virtio carries.

The general notion of no-nsoop should ideally be carried in the PCIe
extended config space flag. If 0 then no-snoop should never be issued,
expected, or requested.

Jason