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From: Dan Williams <dan.j.williams@intel.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Dave Jiang <dave.jiang@intel.com>, Vinod Koul <vkoul@kernel.org>,
	Megha Dey <megha.dey@linux.intel.com>,
	maz@kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>, Yi L Liu <yi.l.liu@intel.com>,
	Baolu Lu <baolu.lu@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	Sanjay K Kumar <sanjay.k.kumar@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>, Jing Lin <jing.lin@intel.com>,
	kwankhede@nvidia.com, eric.auger@redhat.com, parav@mellanox.com,
	dmaengine@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	X86 ML <x86@kernel.org>,
	linux-pci@vger.kernel.org, KVM list <kvm@vger.kernel.org>
Subject: Re: [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver.
Date: Thu, 23 Apr 2020 12:17:50 -0700	[thread overview]
Message-ID: <CAPcyv4hGX5jCzag8oQVUZ6Eq9GvZYLN_6kmBAgQMbrBbNzJ0yg@mail.gmail.com> (raw)
In-Reply-To: <CAPcyv4gMYz1wCYjfnujyGXP0jGehpb+dEYV7hJoAAsDsj9+afQ@mail.gmail.com>

On Wed, Apr 22, 2020 at 2:24 PM Dan Williams <dan.j.williams@intel.com> wrote:
>
> On Tue, Apr 21, 2020 at 4:55 PM Jason Gunthorpe <jgg@mellanox.com> wrote:
> >
> > On Tue, Apr 21, 2020 at 04:33:46PM -0700, Dave Jiang wrote:
> > > The actual code is independent of the stage 2 driver code submission that adds
> > > support for SVM, ENQCMD(S), PASID, and shared workqueues. This code series will
> > > support dedicated workqueue on a guest with no vIOMMU.
> > >
> > > A new device type "mdev" is introduced for the idxd driver. This allows the wq
> > > to be dedicated to the usage of a VFIO mediated device (mdev). Once the work
> > > queue (wq) is enabled, an uuid generated by the user can be added to the wq
> > > through the uuid sysfs attribute for the wq.  After the association, a mdev can
> > > be created using this UUID. The mdev driver code will associate the uuid and
> > > setup the mdev on the driver side. When the create operation is successful, the
> > > uuid can be passed to qemu. When the guest boots up, it should discover a DSA
> > > device when doing PCI discovery.
> >
> > I'm feeling really skeptical that adding all this PCI config space and
> > MMIO BAR emulation to the kernel just to cram this into a VFIO
> > interface is a good idea, that kind of stuff is much safer in
> > userspace.
> >
> > Particularly since vfio is not really needed once a driver is using
> > the PASID stuff. We already have general code for drivers to use to
> > attach a PASID to a mm_struct - and using vfio while disabling all the
> > DMA/iommu config really seems like an abuse.
> >
> > A /dev/idxd char dev that mmaps a bar page and links it to a PASID
> > seems a lot simpler and saner kernel wise.
> >
> > > The mdev utilizes Interrupt Message Store or IMS[3] instead of MSIX for
> > > interrupts for the guest. This preserves MSIX for host usages and also allows a
> > > significantly larger number of interrupt vectors for guest usage.
> >
> > I never did get a reply to my earlier remarks on the IMS patches.
> >
> > The concept of a device specific addr/data table format for MSI is not
> > Intel specific. This should be general code. We have a device that can
> > use this kind of kernel capability today.
>
> This has been my concern reviewing the implementation. IMS needs more
> than one in-tree user to validate degrees of freedom in the api. I had
> been missing a second "in-tree user" to validate the scope of the
> flexibility that was needed.

Hey Jason,

Per Megha's follow-up can you send the details about that other device
and help clear a path for a device-specific MSI addr/data table
format. Ever since HMM I've been sensitive, perhaps overly-sensitive,
to claims about future upstream users. The fact that you have an
additional use case is golden for pushing this into a common area and
validating the scope of the proposed API.

  reply	other threads:[~2020-04-23 19:18 UTC|newest]

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-21 23:33 Dave Jiang
2020-04-21 23:33 ` [PATCH RFC 01/15] drivers/base: Introduce platform_msi_ops Dave Jiang
2020-04-26  7:01   ` Greg KH
2020-04-27 21:38     ` Dave Jiang
2020-04-28  7:34       ` Greg KH
2020-04-21 23:33 ` [PATCH RFC 02/15] drivers/base: Introduce a new platform-msi list Dave Jiang
2020-04-25 21:13   ` Thomas Gleixner
2020-05-04  0:08     ` Dey, Megha
2020-04-21 23:34 ` [PATCH RFC 03/15] drivers/base: Allocate/free platform-msi interrupts by group Dave Jiang
2020-04-25 21:23   ` Thomas Gleixner
2020-05-04  0:08     ` Dey, Megha
2020-04-21 23:34 ` [PATCH RFC 04/15] drivers/base: Add support for a new IMS irq domain Dave Jiang
2020-04-23 20:11   ` Jason Gunthorpe
2020-05-01 22:30     ` Dey, Megha
2020-05-03 22:25       ` Jason Gunthorpe
2020-05-03 22:40         ` Dey, Megha
2020-05-03 22:46           ` Jason Gunthorpe
2020-05-04  0:25             ` Dey, Megha
2020-05-04 12:14               ` Jason Gunthorpe
2020-05-06 10:27                 ` Tian, Kevin
2020-04-25 21:38   ` Thomas Gleixner
2020-05-04  0:11     ` Dey, Megha
2020-04-21 23:34 ` [PATCH RFC 05/15] ims-msi: Add mask/unmask routines Dave Jiang
2020-04-25 21:49   ` Thomas Gleixner
2020-05-04  0:16     ` Dey, Megha
2020-04-21 23:34 ` [PATCH RFC 06/15] ims-msi: Enable IMS interrupts Dave Jiang
2020-04-25 22:13   ` Thomas Gleixner
2020-05-04  0:17     ` Dey, Megha
2020-04-21 23:34 ` [PATCH RFC 07/15] Documentation: Interrupt Message store Dave Jiang
2020-04-23 20:04   ` Jason Gunthorpe
2020-05-01 22:32     ` Dey, Megha
2020-05-03 22:28       ` Jason Gunthorpe
2020-05-03 22:41         ` Dey, Megha
2020-04-21 23:34 ` [PATCH RFC 08/15] vfio/mdev: Add a member for iommu domain in mdev_device Dave Jiang
2020-04-21 23:34 ` [PATCH RFC 09/15] vfio/type1: Save domain when attach domain to mdev Dave Jiang
2020-04-21 23:34 ` [PATCH RFC 10/15] dmaengine: idxd: add config support for readonly devices Dave Jiang
2020-04-21 23:34 ` [PATCH RFC 11/15] dmaengine: idxd: add IMS support in base driver Dave Jiang
2020-04-21 23:35 ` [PATCH RFC 12/15] dmaengine: idxd: add device support functions in prep for mdev Dave Jiang
2020-04-21 23:35 ` [PATCH RFC 13/15] dmaengine: idxd: add support for VFIO mediated device Dave Jiang
2020-04-21 23:35 ` [PATCH RFC 14/15] dmaengine: idxd: add error notification from host driver to " Dave Jiang
2020-04-21 23:35 ` [PATCH RFC 15/15] dmaengine: idxd: add ABI documentation for mediated device support Dave Jiang
2020-04-21 23:54 ` [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver Jason Gunthorpe
2020-04-22  0:53   ` Tian, Kevin
2020-04-22 11:50     ` Jason Gunthorpe
2020-04-22 21:14       ` Raj, Ashok
2020-04-23 19:12         ` Jason Gunthorpe
2020-04-24  3:27           ` Tian, Kevin
2020-04-24 12:44             ` Jason Gunthorpe
2020-04-24 16:25               ` Tian, Kevin
2020-04-24 18:12                 ` Jason Gunthorpe
2020-04-26  5:18                   ` Tian, Kevin
2020-04-26 19:13                     ` Jason Gunthorpe
2020-04-27  3:43                       ` Alex Williamson
2020-04-27 11:58                         ` Jason Gunthorpe
2020-04-27 13:19                           ` Alex Williamson
2020-04-27 13:22                             ` Jason Gunthorpe
2020-04-27 14:18                               ` Alex Williamson
2020-04-27 14:25                                 ` Jason Gunthorpe
2020-04-27 15:41                                   ` Alex Williamson
2020-04-27 16:16                                     ` Jason Gunthorpe
2020-04-27 16:25                                       ` Dave Jiang
2020-04-27 21:56                                         ` Jason Gunthorpe
2020-04-29  9:42                               ` Tian, Kevin
2020-05-08 20:47                                 ` Raj, Ashok
2020-05-08 23:16                                   ` Jason Gunthorpe
2020-05-08 23:52                                     ` Dave Jiang
2020-05-09  0:09                                     ` Raj, Ashok
2020-05-09 12:21                                       ` Jason Gunthorpe
2020-05-13  2:29                                         ` Jason Wang
2020-05-13  8:30                                         ` Tian, Kevin
2020-05-13 12:40                                           ` Jason Gunthorpe
2020-04-27 12:13                       ` Tian, Kevin
2020-04-27 12:55                         ` Jason Gunthorpe
2020-04-22 21:24   ` Dan Williams
2020-04-23 19:17     ` Dan Williams [this message]
2020-04-23 19:49       ` Jason Gunthorpe
2020-05-01 22:31         ` Dey, Megha
2020-05-03 22:21           ` Jason Gunthorpe
2020-05-03 22:32             ` Dey, Megha
2020-04-23 19:18     ` Jason Gunthorpe
2020-05-01 22:31       ` Dey, Megha
2020-05-03 22:22         ` Jason Gunthorpe
2020-05-03 22:31           ` Dey, Megha
2020-05-03 22:36             ` Jason Gunthorpe
2020-05-04  0:20               ` Dey, Megha
2020-04-22 23:04   ` Dey, Megha
2020-04-23 19:44     ` Jason Gunthorpe
2020-05-01 22:32       ` Dey, Megha
2020-04-24  6:31   ` Jason Wang

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