From: Jason Gunthorpe <jgg@nvidia.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "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>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.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 09:06:50 -0300 [thread overview]
Message-ID: <20200807120650.GR16789@nvidia.com> (raw)
In-Reply-To: <87h7tfh6fc.fsf@nanos.tec.linutronix.de>
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.
Jason
next prev parent reply other threads:[~2020-08-07 12:07 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 [this message]
2020-08-07 12:38 ` gregkh
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
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