linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Dan Williams <dan.j.williams@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: "Raj, Ashok" <ashok.raj@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	"Jiang, Dave" <dave.jiang@intel.com>,
	Bjorn Helgaas <helgaas@kernel.org>,
	"vkoul@kernel.org" <vkoul@kernel.org>,
	"Dey, Megha" <megha.dey@intel.com>,
	"maz@kernel.org" <maz@kernel.org>,
	"bhelgaas@google.com" <bhelgaas@google.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	"Lu, Baolu" <baolu.lu@intel.com>,
	"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>,
	"jing.lin@intel.com" <jing.lin@intel.com>,
	"kwankhede@nvidia.com" <kwankhede@nvidia.com>,
	"eric.auger@redhat.com" <eric.auger@redhat.com>,
	"parav@mellanox.com" <parav@mellanox.com>,
	"rafael@kernel.org" <rafael@kernel.org>,
	"netanelg@mellanox.com" <netanelg@mellanox.com>,
	"shahafs@mellanox.com" <shahafs@mellanox.com>,
	"yan.y.zhao@linux.intel.com" <yan.y.zhao@linux.intel.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"Ortiz, Samuel" <samuel.ortiz@intel.com>,
	"Hossain, Mona" <mona.hossain@intel.com>,
	"dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH v4 06/17] PCI: add SIOV and IMS capability detection
Date: Fri, 6 Nov 2020 15:47:00 -0800	[thread overview]
Message-ID: <CAPcyv4iYHA1acfo=+fTk+U_TrLbSWJjA6v4oeTXgVYDTrnCoGw@mail.gmail.com> (raw)
In-Reply-To: <20201106175131.GW2620339@nvidia.com>

On Fri, Nov 6, 2020 at 9:51 AM Jason Gunthorpe <jgg@nvidia.com> wrote:
[..]
> > This is true for IMS as well. But probably not implemented in the kernel as
> > such. From a HW point of view (take idxd for instance) the facility is
> > available to native OS as well. The early RFC supported this for native.
>
> I can't follow what you are trying to say here.

I'm having a hard time following the technical cruxes of this debate.
I grokked your feedback on the original IMS proposal way back at the
beginning of this effort (pre-COVID even!), so maybe I can mediate
here as well. Although, SIOV is that much harder for me to spell than
IMS, so bear with me.

> Dave said the IMS cap was to indicate that the VMM supported emulation
> of IMS so that the VMM can do the MSI addr/data translation as part of
> the emulation.
>
> I'm saying emulation will be too horrible for our devices that don't
> require *any* emulation.

This part I think I understand, i.e. why spend any logic emulating IMS
as MSI since the IMS capability can be a paravirtualized interface
from guest to VMM with none of the compromises that MSI would enforce.
Did I get that right?

> It is a bad architecture. The platform needs to handle this globally
> for all devices, not special hacky emulations things custom made for
> every device out there.

I confess I don't quite understand the shape of what "platform needs
to handle this globally" means, but I understand the desired end
result of "no emulation added where not needed". However, would this
mean that the bare-metal idxd driver can not be used directly in the
guest without modification? For example, as I understand from talking
to Ashok, idxd has some device events like error notification hard
wired to MSI while data patch interrupts are IMS. So even if the IMS
side does not hook up MSI emulation doesn't idxd still need MSI
emulation to reuse the bare metal driver directly?

> > Native devices can have both MSIx and IMS capability. But as I
> > understand this isn't how we have partitioned things in SW today. We
> > left IMS only for mdev's. And I agree this would be very useful.
>
> That split is just some decision idxd did, we are thinking about doing
> other things in our devices.

Where does the collision happen between what you need for a clean
implementation of an IMS-like capability (/me misses his "dev-msi"
name that got thrown out in the Thomas rewrite), and emulation needed
to not have VF special casing in the idxd driver.

Also feel free to straighten me out (Jason or Ashok) if I've botched
the understanding of this.

  reply	other threads:[~2020-11-06 23:47 UTC|newest]

Thread overview: 125+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-30 18:50 [PATCH v4 00/17] Add VFIO mediated device support and DEV-MSI support for the idxd driver Dave Jiang
2020-10-30 18:50 ` [PATCH v4 01/17] irqchip: Add IMS (Interrupt Message Store) driver Dave Jiang
2020-10-30 22:01   ` Thomas Gleixner
2020-10-30 18:51 ` [PATCH v4 02/17] iommu/vt-d: Add DEV-MSI support Dave Jiang
2020-10-30 20:31   ` Thomas Gleixner
2020-10-30 20:52     ` Dave Jiang
2020-10-30 18:51 ` [PATCH v4 03/17] dmaengine: idxd: add theory of operation documentation for idxd mdev Dave Jiang
2020-10-30 18:51 ` [PATCH v4 04/17] dmaengine: idxd: add support for readonly config devices Dave Jiang
2020-10-30 18:51 ` [PATCH v4 05/17] dmaengine: idxd: add interrupt handle request support Dave Jiang
2020-10-30 18:51 ` [PATCH v4 06/17] PCI: add SIOV and IMS capability detection Dave Jiang
2020-10-30 19:51   ` Bjorn Helgaas
2020-10-30 21:20     ` Dave Jiang
2020-10-30 21:50       ` Bjorn Helgaas
2020-10-30 22:45       ` Jason Gunthorpe
2020-10-30 22:49         ` Dave Jiang
2020-11-02 13:21           ` Jason Gunthorpe
2020-11-03  2:49             ` Tian, Kevin
2020-11-03 12:43               ` Jason Gunthorpe
2020-11-04  3:41                 ` Tian, Kevin
2020-11-04 12:40                   ` Jason Gunthorpe
2020-11-04 13:34                     ` Tian, Kevin
2020-11-04 13:54                       ` Jason Gunthorpe
2020-11-06  9:48                         ` Tian, Kevin
2020-11-06 13:14                           ` Jason Gunthorpe
2020-11-06 16:48                             ` Raj, Ashok
2020-11-06 17:51                               ` Jason Gunthorpe
2020-11-06 23:47                                 ` Dan Williams [this message]
2020-11-07  0:12                                   ` Jason Gunthorpe
2020-11-07  1:42                                     ` Dan Williams
2020-11-08 18:11                                     ` Raj, Ashok
2020-11-08 18:34                                       ` David Woodhouse
2020-11-08 23:25                                         ` Raj, Ashok
2020-11-10 14:19                                           ` Raj, Ashok
2020-11-10 14:41                                             ` David Woodhouse
2020-11-08 23:41                                       ` Jason Gunthorpe
2020-11-09  0:05                                         ` Raj, Ashok
2020-11-08 18:47                                     ` Thomas Gleixner
2020-11-08 19:36                                       ` David Woodhouse
2020-11-08 22:47                                         ` Thomas Gleixner
2020-11-08 23:29                                           ` Jason Gunthorpe
2020-11-11 15:41                                         ` Christoph Hellwig
2020-11-11 16:09                                           ` Raj, Ashok
2020-11-11 22:27                                             ` Thomas Gleixner
2020-11-11 23:03                                               ` Raj, Ashok
2020-11-12  1:13                                                 ` Thomas Gleixner
2020-11-12 13:10                                                 ` Jason Gunthorpe
2020-11-08 23:23                                       ` Jason Gunthorpe
2020-11-08 23:36                                         ` Raj, Ashok
2020-11-09  7:37                                         ` Tian, Kevin
2020-11-09 16:46                                           ` Jason Gunthorpe
2020-11-08 23:58                                       ` Raj, Ashok
2020-11-09  7:59                                         ` Tian, Kevin
2020-11-09 11:21                                         ` Thomas Gleixner
2020-11-09 17:30                                           ` Jason Gunthorpe
2020-11-09 22:40                                             ` Raj, Ashok
2020-11-09 22:42                                             ` Thomas Gleixner
2020-11-10  5:14                                               ` Raj, Ashok
2020-11-10 10:27                                                 ` Thomas Gleixner
2020-11-10 14:13                                                   ` Raj, Ashok
2020-11-10 14:23                                                     ` Jason Gunthorpe
2020-11-11  2:17                                                       ` Tian, Kevin
2020-11-12 13:46                                                         ` Jason Gunthorpe
2020-11-11  7:14                                                     ` Tian, Kevin
2020-11-12 19:32                                                       ` Konrad Rzeszutek Wilk
2020-11-12 22:42                                                         ` Thomas Gleixner
2020-11-13  2:42                                                           ` Tian, Kevin
2020-11-13 12:57                                                             ` Jason Gunthorpe
2020-11-13 13:32                                                             ` Thomas Gleixner
2020-11-13 16:12                                                               ` Luck, Tony
2020-11-13 17:38                                                                 ` Raj, Ashok
2020-11-14 10:34                                                           ` Christoph Hellwig
2020-11-14 21:18                                                             ` Raj, Ashok
2020-11-15 11:26                                                               ` Thomas Gleixner
2020-11-15 19:31                                                                 ` Raj, Ashok
2020-11-15 22:11                                                                   ` Thomas Gleixner
2020-11-16  0:22                                                                     ` Raj, Ashok
2020-11-16  7:31                                                                       ` Tian, Kevin
2020-11-16 15:46                                                                         ` Jason Gunthorpe
2020-11-16 17:56                                                                           ` Thomas Gleixner
2020-11-16 18:02                                                                             ` Jason Gunthorpe
2020-11-16 20:37                                                                               ` Thomas Gleixner
2020-11-16 23:51                                                                               ` Tian, Kevin
2020-11-17  9:21                                                                                 ` Thomas Gleixner
2020-11-16  8:25                                                               ` Christoph Hellwig
2020-11-10 14:19                                                 ` Jason Gunthorpe
2020-11-11  2:35                                                   ` Tian, Kevin
2020-11-08 21:18                             ` Thomas Gleixner
2020-11-08 22:09                               ` David Woodhouse
2020-11-08 22:52                                 ` Thomas Gleixner
2020-11-07  0:32                           ` Thomas Gleixner
2020-11-09  5:25                             ` Tian, Kevin
2020-10-30 18:51 ` [PATCH v4 07/17] dmaengine: idxd: add IMS support in base driver Dave Jiang
2020-10-30 18:51 ` [PATCH v4 08/17] dmaengine: idxd: add device support functions in prep for mdev Dave Jiang
2020-10-30 18:51 ` [PATCH v4 09/17] dmaengine: idxd: add basic mdev registration and helper functions Dave Jiang
2020-10-30 18:51 ` [PATCH v4 10/17] dmaengine: idxd: add emulation rw routines Dave Jiang
2020-10-30 18:52 ` [PATCH v4 11/17] dmaengine: idxd: prep for virtual device commands Dave Jiang
2020-10-30 18:52 ` [PATCH v4 12/17] dmaengine: idxd: virtual device commands emulation Dave Jiang
2020-10-30 18:52 ` [PATCH v4 13/17] dmaengine: idxd: ims setup for the vdcm Dave Jiang
2020-10-30 21:26   ` Thomas Gleixner
2020-10-30 18:52 ` [PATCH v4 14/17] dmaengine: idxd: add mdev type as a new wq type Dave Jiang
2020-10-30 18:52 ` [PATCH v4 15/17] dmaengine: idxd: add dedicated wq mdev type Dave Jiang
2020-10-30 18:52 ` [PATCH v4 16/17] dmaengine: idxd: add new wq state for mdev Dave Jiang
2020-10-30 18:52 ` [PATCH v4 17/17] dmaengine: idxd: add error notification from host driver to mediated device Dave Jiang
2020-10-30 18:58 ` [PATCH v4 00/17] Add VFIO mediated device support and DEV-MSI support for the idxd driver Jason Gunthorpe
2020-10-30 19:13   ` Dave Jiang
2020-10-30 19:17     ` Jason Gunthorpe
2020-10-30 19:23       ` Raj, Ashok
2020-10-30 19:30         ` Jason Gunthorpe
2020-10-30 20:43           ` Raj, Ashok
2020-10-30 22:54             ` Jason Gunthorpe
2020-10-31  2:50             ` Thomas Gleixner
2020-10-31 23:53               ` Raj, Ashok
2020-11-02 13:20                 ` Jason Gunthorpe
2020-11-02 16:20                   ` Raj, Ashok
2020-11-02 17:19                     ` Jason Gunthorpe
2020-11-02 18:18                       ` Dave Jiang
2020-11-02 18:26                         ` Jason Gunthorpe
2020-11-02 18:38                           ` Dan Williams
2020-11-02 18:51                             ` Jason Gunthorpe
2020-11-02 19:26                               ` Dan Williams
2020-10-30 20:48 ` Thomas Gleixner
2020-10-30 20:59   ` Dave Jiang
2020-10-30 22:10     ` Thomas Gleixner
     [not found] <draft-875z6ekcj5.fsf@nanos.tec.linutronix.de>
2020-11-09 14:08 ` [PATCH v4 06/17] PCI: add SIOV and IMS capability detection Thomas Gleixner
2020-11-09 18:10   ` Raj, Ashok

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='CAPcyv4iYHA1acfo=+fTk+U_TrLbSWJjA6v4oeTXgVYDTrnCoGw@mail.gmail.com' \
    --to=dan.j.williams@intel.com \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=baolu.lu@intel.com \
    --cc=bhelgaas@google.com \
    --cc=dave.jiang@intel.com \
    --cc=dmaengine@vger.kernel.org \
    --cc=eric.auger@redhat.com \
    --cc=helgaas@kernel.org \
    --cc=jacob.jun.pan@intel.com \
    --cc=jgg@nvidia.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@intel.com \
    --cc=mona.hossain@intel.com \
    --cc=netanelg@mellanox.com \
    --cc=parav@mellanox.com \
    --cc=pbonzini@redhat.com \
    --cc=rafael@kernel.org \
    --cc=samuel.ortiz@intel.com \
    --cc=sanjay.k.kumar@intel.com \
    --cc=shahafs@mellanox.com \
    --cc=tglx@linutronix.de \
    --cc=tony.luck@intel.com \
    --cc=vkoul@kernel.org \
    --cc=yan.y.zhao@linux.intel.com \
    --cc=yi.l.liu@intel.com \
    --subject='Re: [PATCH v4 06/17] PCI: add SIOV and IMS capability detection' \
    /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
on how to clone and mirror all data and code used for this inbox