From: Alex Williamson <alex.williamson@redhat.com>
To: "Yigit, Ferruh" <ferruh.yigit@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] VFIO no-iommu
Date: Tue, 22 Dec 2015 13:20:09 -0700 [thread overview]
Message-ID: <1450815609.2950.8.camel@redhat.com> (raw)
In-Reply-To: <1450725743.3781.56.camel@redhat.com>
On Mon, 2015-12-21 at 12:22 -0700, Alex Williamson wrote:
> On Mon, 2015-12-21 at 11:46 +0000, Yigit, Ferruh wrote:
> > On Fri, Dec 18, 2015 at 02:50:17PM -0700, Alex Williamson wrote:
> > > On Fri, 2015-12-18 at 07:38 -0700, Alex Williamson wrote:
> > > > On Fri, 2015-12-18 at 10:43 +0000, Yigit, Ferruh wrote:
> > > > > On Thu, Dec 17, 2015 at 09:43:59AM -0700, Alex Williamson
> > > > > wrote:
> > > > > <...>
> > > > > > > > > > >
> > > > > > > > > > > Also I need to disable VFIO_CHECK_EXTENSION
> > > > > > > > > > > ioctl,
> > > > > > > > > > > because in
> > > > > > > > > > > vfio
> > > > > > > > > > > module,
> > > > > > > > > > > container->noiommu is not set before doing a
> > > > > > > > > > > vfio_group_set_container()
> > > > > > > > > > > and vfio_for_each_iommu_driver selects wrong
> > > > > > > > > > > driver.
> > > > > > > > > >
> > > > > > > > > > Running CHECK_EXTENSION on a container without the
> > > > > > > > > > group
> > > > > > > > > > attached is
> > > > > > > > > > only going to tell you what extensions vfio is
> > > > > > > > > > capable
> > > > > > > > > > of,
> > > > > > > > > > not
> > > > > > > > > > necessarily what extensions are available to you
> > > > > > > > > > with
> > > > > > > > > > that
> > > > > > > > > > group.
> > > > > > > > > > Is this just a general dpdk- vfio ordering bug?
> > > > > > > > >
> > > > > > > > > Yes, that is how VFIO was implemented in DPDK. I was
> > > > > > > > > under
> > > > > > > > > the
> > > > > > > > > impression that checking extension before assigning
> > > > > > > > > devices
> > > > > > > > > was
> > > > > > > > > the
> > > > > > > > > correct way to do things, so as to not to try
> > > > > > > > > anything
> > > > > > > > > we
> > > > > > > > > know
> > > > > > > > > would
> > > > > > > > > fail anyway. Does this imply that CHECK_EXTENSION
> > > > > > > > > needs
> > > > > > > > > to
> > > > > > > > > be
> > > > > > > > > called
> > > > > > > > > on both container and groups (or just on groups)?
> > > > > > > >
> > > > > > > > Hmm, in Documentation/vfio.txt we do give the following
> > > > > > > > algorithm:
> > > > > > > >
> > > > > > > > if (ioctl(container, VFIO_GET_API_VERSION) !=
> > > > > > > > VFIO_API_VERSION)
> > > > > > > > /* Unknown API version */
> > > > > > > >
> > > > > > > > if (!ioctl(container, VFIO_CHECK_EXTENSION,
> > > > > > > > VFIO_TYPE1_IOMMU))
> > > > > > > > /* Doesn't support the IOMMU driver we
> > > > > > > > want.
> > > > > > > > */
> > > > > > > > ...
> > > > > > > >
> > > > > > > > That's just going to query each iommu driver and we
> > > > > > > > can't
> > > > > > > > yet
> > > > > > > > say
> > > > > > > > whether
> > > > > > > > the group the user attaches to the container later will
> > > > > > > > actually
> > > > > > > > support that
> > > > > > > > extension until we try to do it, that would come at
> > > > > > > > VFIO_SET_IOMMU.
> > > > > > > > So is
> > > > > > > > it perhaps a vfio bug that we're not advertising no-
> > > > > > > > iommu
> > > > > > > > until
> > > > > > > > the
> > > > > > > > group is
> > > > > > > > attached? After all, we are capable of it with just an
> > > > > > > > empty
> > > > > > > > container, just
> > > > > > > > like we are with type1, but we're going to fail
> > > > > > > > SET_IOMMU
> > > > > > > > for
> > > > > > > > the
> > > > > > > > wrong
> > > > > > > > combination.
> > > > > > > > This is exactly the sort of thing that makes me glad
> > > > > > > > we
> > > > > > > > reverted
> > > > > > > > it without
> > > > > > > > feedback from a working user driver. Thanks,
> > > > > > >
> > > > > > > Whether it should be considered a "bug" in VFIO or "by
> > > > > > > design"
> > > > > > > is
> > > > > > > up
> > > > > > > to you, of course, but at least according to the VFIO
> > > > > > > documentation,
> > > > > > > we are meant to check for type 1 extension and then
> > > > > > > attach
> > > > > > > devices,
> > > > > > > so it would be expected to get VFIO_NOIOMMU_IOMMU marked
> > > > > > > as
> > > > > > > supported
> > > > > > > even without any devices attached to the container (just
> > > > > > > like
> > > > > > > we
> > > > > > > get
> > > > > > > type 1 as supported without any devices attached). Having
> > > > > > > said
> > > > > > > that,
> > > > > > > if it was meant to attach devices first and then check
> > > > > > > the
> > > > > > > extensions, then perhaps the documentation should also
> > > > > > > point
> > > > > > > out
> > > > > > > that
> > > > > > > fact (or perhaps I missed that detail in my readings of
> > > > > > > the
> > > > > > > docs,
> > > > > > > in
> > > > > > > which case my apologies).
> > > > > >
> > > > > > Hi Anatoly,
> > > > > >
> > > > > > Does the below patch make it behave more like you'd expect.
> > > > > > This
> > > > > > applies to v4.4-rc4, I'd fold this into the base patch if
> > > > > > we
> > > > > > reincorporate it to a future kernel. Thanks,
> > > > > >
> > > > > > Alex
> > > > > >
> > > > > > commit 88d4dcb6b77624965f0b45b5cd305a2b4a105c94
> > > > > > Author: Alex Williamson <alex.williamson@redhat.com>
> > > > > > Date: Wed Dec 16 19:02:01 2015 -0700
> > > > > >
> > > > > > vfio: Fix no-iommu CHECK_EXTENSION
> > > > > >
> > > > > > Previously the no-iommu iommu driver was only visible
> > > > > > when
> > > > > > the
> > > > > > container had an attached no-iommu group. This means
> > > > > > that
> > > > > > CHECK_EXTENSION on and empty container couldn't report
> > > > > > the
> > > > > > possibility
> > > > > > of using VFIO_NOIOMMU_IOMMU. We report TYPE1 whether
> > > > > > or
> > > > > > not
> > > > > > the user
> > > > > > can make use of it with the group, so this is
> > > > > > inconsistent. Add the
> > > > > > no-iommu iommu to the list of iommu drivers when
> > > > > > enabled
> > > > > > via
> > > > > > module
> > > > > > option, but skip all the others if the container is
> > > > > > attached
> > > > > > to
> > > > > > a
> > > > > > no-iommu groups. Note that tainting is now done with
> > > > > > the
> > > > > > "unsafe"
> > > > > > module callback rather than explictly within vfio.
> > > > > >
> > > > > > Also fixes module option and module description name
> > > > > > inconsistency.
> > > > > >
> > > > > > Also make vfio_noiommu_ops const.
> > > > > >
> > > > > > Signed-off-by: Alex Williamson <alex.williamson@redhat.
> > > > > > co
> > > > > > m>
> > > > >
> > > > > Hi Alex,
> > > > >
> > > > > I got following crash with this update:
> > >
> > > Let's try this one:
> > >
> > > commit 8ff839c6ffe9f3b50b50f1cc87e7afbf23171f05
> > > Author: Alex Williamson <alex.williamson@redhat.com>
> > > Date: Fri Dec 18 14:45:55 2015 -0700
> > >
> > > v2 vfio fix no-iommu CHECK_EXTENSION
> > >
> > > Register and unregister the no-iommu iommu backend at module
> > > initialization and exit, but disable it unless enabled via
> > > module
> > > option. Rather than modify the iommu driver walk,
> > > selectively
> > > skip
> > > combinations that aren't supported. CHECK_EXTENSION on a
> > > container
> > > without any groups attached exposes all possible
> > > extensions. Once a
> > > group is attached, the no-iommu backend is skipped for
> > > regular
> > > groups
> > > and regular iommu backends are skipped for no-iommu groups.
> > >
> > > This would be folded into a single patch to re-propose vfio
> > > no-
> > > iommu
> > > mode upstream.
> > >
> > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > >
> > Hi Alex,
> >
> > Thank you for the update. I have tested this on both no-iommu and
> > iommu environment
> > and worked successfully. I believe this approach is better because
> > it
> > is simpler.
> >
> > From DPDK point of view, only update to support vfio no-iommu is:
> > to
> > use new group names
> > and disable DMA mapping.
> >
> > If VFIO module compiled with "CONFIG_VFIO_NOIOMMU=y" by default,
> > that
> > makes things easier
> > for DPDK, in no-iommu environment inserting vfio module with proper
> > parameter makes it
> > available for DPDK.
>
> Thanks for the update Ferruh. Also note that the module option is
> dynamically settable so that it can support running with statically
> compiled modules where you may not know whether or not to enable no-
> iommu until after boot, or where unloading and re-loading a module
> might not be an option. It will be up to each distro to decide
> whether
> to enable the config option, but I think we at least highlight the
> existing support issue for non-iommu protected userspace drivers,
> which
> is something that was not at all clear with the uio driver approach.
Hi,
I've re-posted the unified patch upstream and it should start showing
up in the next linux-next build. I expect the dpdk code won't be
merged until after this gets back into a proper kernel, but could we
get the dpdk modifications posted as rfc for others looking to try it?
Thanks,
Alex
next prev parent reply other threads:[~2015-12-22 20:20 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-11 16:28 Thomas Monjalon
2015-12-11 22:12 ` Vincent JARDIN
2015-12-11 23:02 ` Alex Williamson
2015-12-15 13:43 ` O'Driscoll, Tim
2015-12-15 16:53 ` Alex Williamson
2015-12-16 4:04 ` Ferruh Yigit
2015-12-16 4:38 ` Alex Williamson
2015-12-16 8:35 ` Burakov, Anatoly
2015-12-16 16:23 ` Burakov, Anatoly
2015-12-16 23:17 ` Thomas Monjalon
2015-12-17 9:52 ` Burakov, Anatoly
2015-12-17 10:09 ` Thomas Monjalon
2015-12-17 19:38 ` Jan Viktorin
2015-12-17 21:16 ` Vincent JARDIN
2015-12-17 23:29 ` Stephen Hemminger
2015-12-16 17:11 ` Alex Williamson
2015-12-16 17:22 ` Burakov, Anatoly
2015-12-17 16:43 ` Alex Williamson
2015-12-18 10:43 ` Yigit, Ferruh
2015-12-18 14:38 ` Alex Williamson
2015-12-18 21:50 ` Alex Williamson
2015-12-21 11:46 ` Yigit, Ferruh
2015-12-21 12:18 ` [dpdk-dev] [PATCH] vfio: add no-iommu support Ferruh Yigit
2015-12-21 15:15 ` Burakov, Anatoly
2015-12-21 15:26 ` Yigit, Ferruh
2015-12-21 15:28 ` Burakov, Anatoly
2015-12-21 19:22 ` [dpdk-dev] VFIO no-iommu Alex Williamson
2015-12-22 20:20 ` Alex Williamson [this message]
2015-12-23 11:19 ` Burakov, Anatoly
2015-12-31 14:30 ` Santosh Shukla
2016-01-14 6:03 ` Jike Song
2016-01-14 6:52 ` Alex Williamson
2016-01-14 8:12 ` Jike Song
2015-12-11 23:20 ` Jan Viktorin
2015-12-15 11:20 ` Alejandro Lucero
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