linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jason Gunthorpe <jgg@mellanox.com>
To: Dan Williams <dan.j.williams@intel.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@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 16:18:46 -0300	[thread overview]
Message-ID: <20200423191846.GE13640@mellanox.com> (raw)
In-Reply-To: <CAPcyv4gMYz1wCYjfnujyGXP0jGehpb+dEYV7hJoAAsDsj9+afQ@mail.gmail.com>

On Wed, Apr 22, 2020 at 02:24:11PM -0700, Dan Williams 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.

IMS is too narrowly specified.

All platforms that support MSI today can support IMS. It is simply a
way for the platform to give the driver an addr/data pair that triggers
an interrupt when a posted write is performed to that pair.

This is different from the other interrupt setup flows which are
tightly tied to the PCI layer. Here the driver should simply ask for
interrupts.

Ie the entire IMS API to the driver should be something very simple
like:

 struct message_irq
 {
   uint64_t addr;
   uint32_t data;
 };

 struct message_irq *request_message_irq(
    struct device *, irq_handler_t handler, unsigned long flags,
    const char *name, void *dev);

And the plumbing underneath should setup the irq chips and so forth as
required.

Jason

  parent 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
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 [this message]
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

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=20200423191846.GE13640@mellanox.com \
    --to=jgg@mellanox.com \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=baolu.lu@intel.com \
    --cc=bhelgaas@google.com \
    --cc=dan.j.williams@intel.com \
    --cc=dave.jiang@intel.com \
    --cc=dmaengine@vger.kernel.org \
    --cc=eric.auger@redhat.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=hpa@zytor.com \
    --cc=jacob.jun.pan@intel.com \
    --cc=jing.lin@intel.com \
    --cc=kevin.tian@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=kwankhede@nvidia.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=maz@kernel.org \
    --cc=megha.dey@linux.intel.com \
    --cc=parav@mellanox.com \
    --cc=rafael@kernel.org \
    --cc=sanjay.k.kumar@intel.com \
    --cc=tglx@linutronix.de \
    --cc=tony.luck@intel.com \
    --cc=vkoul@kernel.org \
    --cc=x86@kernel.org \
    --cc=yi.l.liu@intel.com \
    --subject='Re: [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver.' \
    /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

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).