From: Jason Gunthorpe <jgg@mellanox.com>
To: "Dey, Megha" <megha.dey@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
Dave Jiang <dave.jiang@intel.com>, Vinod Koul <vkoul@kernel.org>,
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: Sun, 3 May 2020 19:36:18 -0300 [thread overview]
Message-ID: <20200503223618.GG19158@mellanox.com> (raw)
In-Reply-To: <5bc05b74-536f-f72d-c406-18644436f11b@linux.intel.com>
On Sun, May 03, 2020 at 03:31:39PM -0700, Dey, Megha wrote:
>
> Hi Jason,
>
> On 5/3/2020 3:22 PM, Jason Gunthorpe wrote:
> > On Fri, May 01, 2020 at 03:31:51PM -0700, Dey, Megha wrote:
> > > > > 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.
> > > >
> > >
> > > Well, yes and no. IMS requires interrupt remapping in addition to the
> > > dynamic nature of IRQ allocation.
> >
> > You've mentioned remapping a few times, but I really can't understand
> > why it has anything to do with platform_msi or IMS..
>
> So after some internal discussions, we have concluded that IMS has no
> linkage with Interrupt remapping, IR is just a platform concept. IMS is just
> a name Intel came up with, all it really means is device managed addr/data
> writes to generate interrupts. Technically we can call something IMS even if
> device has its own location to store interrupts in non-pci standard
> mechanism, much like platform-msi indeed. We simply need to extend
> platform-msi to its address some of its shortcomings: increase number of
> interrupts to > 2048, enable dynamic allocation of interrupts, add
> mask/unmask callbacks in addition to write_msg etc.
Sounds right to me
Persumably you still need a way for the driver, eg vfio, to ensure a
MSI is remappable, but shouldn't that be exactly the same way as done
in normal PCI MSI today?
> FWIW, even MSI can be IMS with rules on how to manage the addr/data writes
> following pci sig .. its just that.
Yep, IMHO, our whole handling of MSI is very un-general sometimes..
I thought the msi_domain stuff that some platforms are using is a way
to improve on that? You might find that updating x86 to use msi_domain
might be helpful in this project???
Jason
next prev parent reply other threads:[~2020-05-03 22:36 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 23:33 [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver 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
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 [this message]
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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