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From: Jason Gunthorpe <jgg@mellanox.com>
To: Dave Jiang <dave.jiang@intel.com>
Cc: vkoul@kernel.org, megha.dey@linux.intel.com, maz@kernel.org,
	bhelgaas@google.com, rafael@kernel.org,
	gregkh@linuxfoundation.org, tglx@linutronix.de, hpa@zytor.com,
	alex.williamson@redhat.com, jacob.jun.pan@intel.com,
	ashok.raj@intel.com, yi.l.liu@intel.com, baolu.lu@intel.com,
	kevin.tian@intel.com, sanjay.k.kumar@intel.com,
	tony.luck@intel.com, jing.lin@intel.com,
	dan.j.williams@intel.com, kwankhede@nvidia.com,
	eric.auger@redhat.com, parav@mellanox.com,
	dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
	x86@kernel.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver.
Date: Tue, 21 Apr 2020 20:54:42 -0300	[thread overview]
Message-ID: <20200421235442.GO11945@mellanox.com> (raw)
In-Reply-To: <158751095889.36773.6009825070990637468.stgit@djiang5-desk3.ch.intel.com>

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.

Jason

  parent reply	other threads:[~2020-04-21 23:54 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 ` Jason Gunthorpe [this message]
2020-04-22  0:53   ` [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver 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
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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