From: "Michael S. Tsirkin" <mst@redhat.com>
To: Gleb Natapov <gleb@scylladb.com>
Cc: Avi Kivity <avi@scylladb.com>,
Alex Williamson <alex.williamson@redhat.com>,
Vlad Zolotarov <vladz@cloudius-systems.com>,
Greg KH <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, hjk@hansjkoch.de, corbet@lwn.net,
bruce.richardson@intel.com, avi@cloudius-systems.com,
gleb@cloudius-systems.com, stephen@networkplumber.org,
alexander.duyck@gmail.com
Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support
Date: Thu, 8 Oct 2015 20:39:10 +0300 [thread overview]
Message-ID: <20151008200301-mutt-send-email-mst@redhat.com> (raw)
In-Reply-To: <20151008170121.GA2013@scylladb.com>
On Thu, Oct 08, 2015 at 08:01:21PM +0300, Gleb Natapov wrote:
> On Thu, Oct 08, 2015 at 07:43:04PM +0300, Michael S. Tsirkin wrote:
> > On Thu, Oct 08, 2015 at 04:28:34PM +0300, Gleb Natapov wrote:
> > > On Thu, Oct 08, 2015 at 04:20:04PM +0300, Michael S. Tsirkin wrote:
> > > > On Thu, Oct 08, 2015 at 03:27:37PM +0300, Gleb Natapov wrote:
> > > > > On Thu, Oct 08, 2015 at 03:06:07PM +0300, Michael S. Tsirkin wrote:
> > > > > > On Thu, Oct 08, 2015 at 12:44:09PM +0300, Avi Kivity wrote:
> > > > > > >
> > > > > > >
> > > > > > > On 10/08/2015 12:16 PM, Michael S. Tsirkin wrote:
> > > > > > > >On Thu, Oct 08, 2015 at 11:46:30AM +0300, Avi Kivity wrote:
> > > > > > > >>
> > > > > > > >>On 10/08/2015 10:32 AM, Michael S. Tsirkin wrote:
> > > > > > > >>>On Thu, Oct 08, 2015 at 08:33:45AM +0300, Avi Kivity wrote:
> > > > > > > >>>>It is good practice to defend against root oopsing the kernel, but in some
> > > > > > > >>>>cases it cannot be achieved.
> > > > > > > >>>Absolutely. That's one of the issues with these patches. They don't even
> > > > > > > >>>try where it's absolutely possible.
> > > > > > > >>>
> > > > > > > >>Are you referring to blocking the maps of the msix BAR areas?
> > > > > > > >For example. There are more. I listed some of the issues on the mailing
> > > > > > > >list, and I might have missed some. VFIO has code to address all this,
> > > > > > > >people should share code to avoid duplication, or at least read it
> > > > > > > >to understand the issues.
> > > > > > >
> > > > > > > All but one of those are unrelated to the patch that adds msix support.
> > > > > >
> > > > > > They are related because msix support enables bus mastering. Without it
> > > > > > device is passive and can't harm anyone. With it, suddently you need to
> > > > > > be very careful with the device to avoid corrupting kernel memory.
> > > > > >
> > > > > Most (if not all) uio_pci_generic users enable pci bus mastering. The
> > > > > fact that they do that without even tainting the kernel like the patch
> > > > > does make current situation much worse that with the patch.
> > > >
> > > > It isn't worse. It's a sane interface. Whoever enables bus mastering
> > > > must be careful. If userspace enables bus mastering then userspace
> > > > needs to be very careful with the device to avoid corrupting kernel
> > > > memory. If kernel does it, it's kernel's responsibility.
> > > >
> > > Although this definition of sanity sounds strange to me, but lets
> > > flow with it for the sake of this email: would it be OK if proposed
> > > interface refused to work if bus mastering is not already enabled by
> > > userspace?
> >
> > An interface could be acceptable if there's a fallback where it
> > works without BM but slower (e.g. poll pending bits).
> >
> OK.
>
> > But not the proposed one.
> >
> Why? Greg is against ioctl interface so it will be reworked, by besides
> that what is wrong with the concept of binding msi-x interrupt to
> eventfd?
It's not the binding. Managing msi-x just needs more than the puny
2 ioctls to get # of vectors and set eventfd.
It interacts in strange ways with reset, and with PM, and ...
> > Really, there's more to making msi-x work with
> > userspace drivers than this patch. As I keep telling people, you would
> > basically reimplement vfio/pci. Go over it, and see for yourself.
> > Almost everything it does is relevant for msi-x. It's just wrong to
> > duplicate so much code.
> >
> The patch is tested and works with msi-x. Restricting access to msi-x
> registers that vfio does is not relevant here.
It works *for you* with a specific userspace application. I have no idea
how you tested it, and what does the userspace in question do. But it
seems pretty clear that there are a ton of very reasonable things that
one can do with a device and that break when you enable MSI-X.
You need to find a way to share that logic with vfio/pci.
> --
> Gleb.
next prev parent reply other threads:[~2015-10-08 17:39 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-04 20:43 [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Vlad Zolotarov
2015-10-04 20:43 ` [PATCH v3 1/3] uio: add ioctl support Vlad Zolotarov
2015-10-05 3:03 ` Greg KH
2015-10-05 7:33 ` Vlad Zolotarov
2015-10-05 8:01 ` Greg KH
2015-10-05 10:36 ` Vlad Zolotarov
2015-10-05 20:02 ` Michael S. Tsirkin
[not found] ` <CAOYyTHZ2=UCYxuJKvd5S6qxp=84DBq5bMadg5wL0rFLZBh2-8Q@mail.gmail.com>
2015-10-05 22:29 ` Michael S. Tsirkin
2015-10-06 8:33 ` Vlad Zolotarov
2015-10-06 14:19 ` Michael S. Tsirkin
2015-10-06 14:30 ` Gleb Natapov
2015-10-06 15:19 ` Michael S. Tsirkin
2015-10-06 15:31 ` Vlad Zolotarov
2015-10-06 15:57 ` Gleb Natapov
2015-10-04 20:43 ` [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov
2015-10-05 3:11 ` Greg KH
2015-10-05 7:41 ` Vlad Zolotarov
2015-10-05 7:56 ` Greg KH
2015-10-05 10:48 ` Vlad Zolotarov
2015-10-05 10:57 ` Greg KH
2015-10-05 11:09 ` Avi Kivity
2015-10-05 13:08 ` Greg KH
2015-10-05 11:41 ` Vlad Zolotarov
2015-10-05 11:47 ` Avi Kivity
2015-10-05 11:53 ` Vlad Zolotarov
2015-10-05 8:28 ` Avi Kivity
2015-10-05 9:49 ` Greg KH
2015-10-05 10:20 ` Avi Kivity
2015-10-06 14:38 ` Michael S. Tsirkin
2015-10-06 14:43 ` Vlad Zolotarov
2015-10-06 14:56 ` Michael S. Tsirkin
2015-10-06 15:23 ` Avi Kivity
2015-10-06 18:51 ` Alex Williamson
2015-10-06 21:32 ` Stephen Hemminger
2015-10-06 21:41 ` Alex Williamson
[not found] ` <CAOaVG152OrQz-Bbnpr0VeE+vLH7nMGsG6A3sD7eTQHormNGVUg@mail.gmail.com>
2015-10-07 7:57 ` Vlad Zolotarov
[not found] ` <5614C160.6000203@scylladb.com>
2015-10-07 8:00 ` Vlad Zolotarov
2015-10-07 8:01 ` Vlad Zolotarov
2015-10-07 6:52 ` Avi Kivity
2015-10-07 16:31 ` Alex Williamson
2015-10-07 16:39 ` Avi Kivity
2015-10-07 21:05 ` Michael S. Tsirkin
2015-10-08 4:19 ` Gleb Natapov
2015-10-08 7:41 ` Michael S. Tsirkin
2015-10-08 7:59 ` Gleb Natapov
2015-10-08 9:38 ` Michael S. Tsirkin
2015-10-08 9:45 ` Gleb Natapov
2015-10-08 12:15 ` Michael S. Tsirkin
2015-10-08 5:33 ` Avi Kivity
2015-10-08 7:32 ` Michael S. Tsirkin
2015-10-08 8:46 ` Avi Kivity
2015-10-08 9:16 ` Michael S. Tsirkin
2015-10-08 9:44 ` Avi Kivity
2015-10-08 12:06 ` Michael S. Tsirkin
2015-10-08 12:27 ` Gleb Natapov
2015-10-08 13:20 ` Michael S. Tsirkin
2015-10-08 13:28 ` Gleb Natapov
2015-10-08 16:43 ` Michael S. Tsirkin
2015-10-08 17:01 ` Gleb Natapov
2015-10-08 17:39 ` Michael S. Tsirkin [this message]
2015-10-08 17:53 ` Gleb Natapov
2015-10-08 18:38 ` Greg KH
2015-10-08 8:32 ` Michael S. Tsirkin
2015-10-08 8:52 ` Gleb Natapov
2015-10-08 9:19 ` Avi Kivity
2015-10-08 10:26 ` Michael S. Tsirkin
2015-10-08 13:20 ` Avi Kivity
2015-10-08 14:17 ` Michael S. Tsirkin
2015-10-08 15:31 ` Alex Williamson
2015-10-07 20:05 ` Michael S. Tsirkin
2015-10-07 7:55 ` Vlad Zolotarov
2015-10-08 8:48 ` Michael S. Tsirkin
2015-10-06 15:28 ` Vlad Zolotarov
2015-10-06 14:46 ` Michael S. Tsirkin
2015-10-06 15:27 ` Avi Kivity
2015-10-05 8:41 ` Stephen Hemminger
2015-10-05 9:08 ` Vlad Zolotarov
2015-10-05 10:06 ` Vlad Zolotarov
2015-10-05 20:09 ` Michael S. Tsirkin
2015-10-05 9:11 ` Vlad Zolotarov
2015-10-05 19:16 ` Michael S. Tsirkin
2015-10-04 20:43 ` [PATCH v3 3/3] Documentation: update uio-howto Vlad Zolotarov
2015-10-04 20:45 ` [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Vlad Zolotarov
2015-10-05 19:50 ` Michael S. Tsirkin
2015-10-06 8:37 ` Vlad Zolotarov
2015-10-06 14:30 ` Michael S. Tsirkin
2015-10-06 14:40 ` Vlad Zolotarov
2015-10-06 15:13 ` Michael S. Tsirkin
2015-10-06 16:35 ` Vlad Zolotarov
2015-10-06 15:11 ` Avi Kivity
2015-10-06 15:15 ` Michael S. Tsirkin
2015-10-06 16:00 ` Gleb Natapov
2015-10-06 16:09 ` Avi Kivity
2015-10-07 10:25 ` Michael S. Tsirkin
2015-10-07 10:28 ` Avi Kivity
-- strict thread matches above, loose matches on Subject: below --
2015-10-04 20:39 Vlad Zolotarov
2015-10-04 20:39 ` [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20151008200301-mutt-send-email-mst@redhat.com \
--to=mst@redhat.com \
--cc=alex.williamson@redhat.com \
--cc=alexander.duyck@gmail.com \
--cc=avi@cloudius-systems.com \
--cc=avi@scylladb.com \
--cc=bruce.richardson@intel.com \
--cc=corbet@lwn.net \
--cc=gleb@cloudius-systems.com \
--cc=gleb@scylladb.com \
--cc=gregkh@linuxfoundation.org \
--cc=hjk@hansjkoch.de \
--cc=linux-kernel@vger.kernel.org \
--cc=stephen@networkplumber.org \
--cc=vladz@cloudius-systems.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).