From: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"Dey, Megha" <megha.dey@intel.com>, Marc Zyngier <maz@kernel.org>,
"Jiang, Dave" <dave.jiang@intel.com>,
"vkoul@kernel.org" <vkoul@kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"rafael@kernel.org" <rafael@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>,
"Lu, Baolu" <baolu.lu@intel.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Lin, Jing" <jing.lin@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"kwankhede@nvidia.com" <kwankhede@nvidia.com>,
"eric.auger@redhat.com" <eric.auger@redhat.com>,
"parav@mellanox.com" <parav@mellanox.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"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>,
"x86@kernel.org" <x86@kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV_MSI irq domain
Date: Fri, 7 Aug 2020 14:38:31 +0200 [thread overview]
Message-ID: <20200807123831.GA645281@kroah.com> (raw)
In-Reply-To: <20200807120650.GR16789@nvidia.com>
On Fri, Aug 07, 2020 at 09:06:50AM -0300, Jason Gunthorpe wrote:
> On Thu, Aug 06, 2020 at 10:21:11PM +0200, Thomas Gleixner wrote:
>
> > Optionally? Please tell the hardware folks to make this mandatory. We
> > have enough pain with non maskable MSI interrupts already so introducing
> > yet another non maskable interrupt trainwreck is not an option.
>
> Can you elaborate on the flows where Linux will need to trigger
> masking?
>
> I expect that masking will be available in our NIC HW too - but it
> will require a spin loop if masking has to be done in an atomic
> context.
>
> > It's more than a decade now that I tell HW people not to repeat the
> > non-maskable MSI failure, but obviously they still think that
> > non-maskable interrupts are a brilliant idea. I know that HW folks
> > believe that everything they omit can be fixed in software, but they
> > have to finally understand that this particular issue _cannot_ be fixed
> > at all.
>
> Sure, the CPU should always be able to shut off an interrupt!
>
> Maybe explaining the goals would help understand the HW perspective.
>
> Today HW can process > 100k queues of work at once. Interrupt delivery
> works by having a MSI index in each queue's metadata and the interrupt
> indirects through a MSI-X table on-chip which has the
> addr/data/mask/etc.
>
> What IMS proposes is that the interrupt data can move into the queue
> meta data (which is not required to be on-chip), eg along side the
> producer/consumer pointers, and the central MSI-X table is not
> needed. This is necessary because the PCI spec has very harsh design
> requirements for a MSI-X table that make scaling it prohibitive.
>
> So an IRQ can be silenced by deleting or stopping the queue(s)
> triggering it. It can be masked by including masking in the queue
> metadata. We can detect pending by checking the producer/consumer
> values.
>
> However synchronizing all the HW and all the state is now more
> complicated than just writing a mask bit via MMIO to an on-die memory.
Because doing all of the work that used to be done in HW in software is
so much faster and scalable? Feels really wrong to me :(
Do you all have a pointer to the spec for this newly proposed stuff
anywhere to try to figure out how the HW wants this to all work?
thanks,
greg k-h
next prev parent reply other threads:[~2020-08-07 12:38 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 16:02 [PATCH RFC v2 00/18] Add VFIO mediated device support and DEV-MSI support for the idxd driver Dave Jiang
2020-07-21 16:02 ` [PATCH RFC v2 01/18] platform-msi: Introduce platform_msi_ops Dave Jiang
2020-07-21 16:02 ` [PATCH RFC v2 02/18] irq/dev-msi: Add support for a new DEV_MSI irq domain Dave Jiang
2020-07-21 16:13 ` Jason Gunthorpe
2020-07-22 16:50 ` Dey, Megha
2020-07-22 18:52 ` Marc Zyngier
2020-07-22 19:59 ` Jason Gunthorpe
2020-07-23 8:51 ` Marc Zyngier
2020-07-24 0:16 ` Jason Gunthorpe
2020-07-24 0:36 ` Thomas Gleixner
2020-08-05 19:18 ` Dey, Megha
2020-08-05 22:15 ` Jason Gunthorpe
2020-08-05 22:36 ` Dey, Megha
2020-08-05 22:53 ` Jason Gunthorpe
2020-08-06 0:13 ` Dey, Megha
2020-08-06 0:19 ` Jason Gunthorpe
2020-08-06 0:32 ` Dey, Megha
2020-08-06 0:46 ` Jason Gunthorpe
2020-08-06 17:10 ` Thomas Gleixner
2020-08-06 17:58 ` Dey, Megha
2020-08-06 20:21 ` Thomas Gleixner
2020-08-06 22:27 ` Dey, Megha
2020-08-07 8:48 ` Thomas Gleixner
2020-08-07 12:06 ` Jason Gunthorpe
2020-08-07 12:38 ` gregkh [this message]
2020-08-07 13:34 ` Jason Gunthorpe
2020-08-07 16:47 ` Thomas Gleixner
2020-08-07 17:54 ` Dey, Megha
2020-08-07 18:39 ` Jason Gunthorpe
2020-08-07 20:31 ` Dey, Megha
2020-08-08 19:47 ` Thomas Gleixner
2020-08-10 21:46 ` Thomas Gleixner
2020-08-11 9:53 ` Thomas Gleixner
2020-08-11 18:46 ` Dey, Megha
2020-08-11 21:25 ` Thomas Gleixner
2020-08-11 18:39 ` Dey, Megha
2020-08-11 22:39 ` Thomas Gleixner
2020-08-07 15:22 ` Thomas Gleixner
2020-08-05 18:55 ` Dey, Megha
2020-07-21 16:02 ` [PATCH RFC v2 03/18] irq/dev-msi: Create IR-DEV-MSI " Dave Jiang
2020-07-21 16:21 ` Jason Gunthorpe
2020-07-22 17:03 ` Dey, Megha
2020-07-22 17:33 ` Jason Gunthorpe
2020-07-22 20:44 ` Thomas Gleixner
2020-08-05 19:02 ` Dey, Megha
2020-07-21 16:02 ` [PATCH RFC v2 04/18] irq/dev-msi: Introduce APIs to allocate/free dev-msi interrupts Dave Jiang
2020-07-21 16:25 ` Jason Gunthorpe
2020-07-22 17:05 ` Dey, Megha
2020-07-22 17:35 ` Jason Gunthorpe
2020-08-05 20:19 ` Dey, Megha
2020-07-21 16:02 ` [PATCH RFC v2 05/18] dmaengine: idxd: add support for readonly config devices Dave Jiang
2020-07-21 16:02 ` [PATCH RFC v2 06/18] dmaengine: idxd: add interrupt handle request support Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 07/18] dmaengine: idxd: add DEV-MSI support in base driver Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 08/18] dmaengine: idxd: add device support functions in prep for mdev Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 09/18] dmaengine: idxd: add basic mdev registration and helper functions Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 10/18] dmaengine: idxd: add emulation rw routines Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 11/18] dmaengine: idxd: prep for virtual device commands Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 12/18] dmaengine: idxd: virtual device commands emulation Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 13/18] dmaengine: idxd: ims setup for the vdcm Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 14/18] dmaengine: idxd: add mdev type as a new wq type Dave Jiang
2020-07-21 16:03 ` [PATCH RFC v2 15/18] dmaengine: idxd: add dedicated wq mdev type Dave Jiang
2020-07-21 16:04 ` [PATCH RFC v2 16/18] dmaengine: idxd: add new wq state for mdev Dave Jiang
2020-07-21 16:04 ` [PATCH RFC v2 17/18] dmaengine: idxd: add error notification from host driver to mediated device Dave Jiang
2020-07-21 16:04 ` [PATCH RFC v2 18/18] dmaengine: idxd: add ABI documentation for mediated device support Dave Jiang
2020-07-21 16:28 ` [PATCH RFC v2 00/18] Add VFIO mediated device support and DEV-MSI support for the idxd driver Greg KH
2020-07-21 17:17 ` Dave Jiang
2020-07-21 21:35 ` Dan Williams
2020-07-21 16:45 ` Jason Gunthorpe
2020-07-21 18:00 ` Dave Jiang
2020-07-22 17:31 ` Dey, Megha
2020-07-22 18:16 ` Jason Gunthorpe
2020-07-21 23:54 ` Tian, Kevin
2020-07-24 0:19 ` Jason Gunthorpe
2020-08-06 1:22 ` Alex Williamson
2020-08-07 12:19 ` Jason Gunthorpe
2020-08-10 7:32 ` Tian, Kevin
2020-08-11 17:00 ` Alex Williamson
2020-08-12 1:58 ` Tian, Kevin
2020-08-12 2:36 ` Alex Williamson
2020-08-12 3:35 ` Tian, Kevin
2020-08-12 3:28 ` Jason Wang
2020-08-12 4:05 ` Tian, Kevin
2020-08-13 4:33 ` Jason Wang
2020-08-13 5:26 ` Tian, Kevin
2020-08-13 6:01 ` Jason Wang
2020-08-14 13:23 ` Jason Gunthorpe
2020-08-17 2:24 ` Tian, Kevin
2020-08-14 13:35 ` Jason Gunthorpe
2020-08-17 2:12 ` Tian, Kevin
2020-08-18 0:43 ` Jason Gunthorpe
2020-08-18 1:09 ` Tian, Kevin
2020-08-18 11:50 ` Jason Gunthorpe
2020-08-18 16:27 ` Paolo Bonzini
2020-08-18 16:49 ` Jason Gunthorpe
2020-08-18 17:05 ` Paolo Bonzini
2020-08-18 17:18 ` Jason Gunthorpe
2020-08-19 7:29 ` Tian, Kevin
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=20200807123831.GA645281@kroah.com \
--to=gregkh@linuxfoundation.org \
--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.hansen@intel.com \
--cc=dave.jiang@intel.com \
--cc=dmaengine@vger.kernel.org \
--cc=eric.auger@redhat.com \
--cc=hpa@zytor.com \
--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=x86@kernel.org \
--cc=yan.y.zhao@linux.intel.com \
--cc=yi.l.liu@intel.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).