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From: Jason Gunthorpe <jgg@ziepe.ca>
To: "Radovanovic, Aleksandar" <aleksandar.radovanovic@amd.com>
Cc: "Gupta, Nipun" <Nipun.Gupta@amd.com>,
	Marc Zyngier <maz@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
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	"Anand, Harpreet" <harpreet.anand@amd.com>,
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	"git (AMD-Xilinx)" <git@amd.com>
Subject: Re: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its domain as parent
Date: Wed, 12 Oct 2022 11:38:29 -0300	[thread overview]
Message-ID: <Y0bRZTP9Kc6mdCiu@ziepe.ca> (raw)
In-Reply-To: <MN2PR12MB4358A871519748CD7A6DB7A089229@MN2PR12MB4358.namprd12.prod.outlook.com>

On Wed, Oct 12, 2022 at 01:37:54PM +0000, Radovanovic, Aleksandar wrote:
> > On Wed, Oct 12, 2022 at 10:34:23AM +0000, Radovanovic, Aleksandar wrote:
> > 
> > 
> > > As for GITS_TRANSLATER, we can take up to 4 different IOVAs, which
> > > limits us to 4 CDX devices (should be sufficient for current HW
> > > use-cases). Also, it means that the address part must be the same for
> > > all vectors within a single CDX device. I'm assuming this is OK as it
> > > is going to be a single interrupt and IOMMU domain anyway.
> > 
> > This is not at all how MSI is supposed to work.
> 
> In the general case, no, they're not.

I don't mean that you can hack this to work - I mean that in MSI the
addr/data is supposed to come from the end point itself, not from some
kind of shared structure. This is important because the actual act of
generating the write has to be coherent with the DMA the device is
doing, as the MSI write must push any DMA data to visibility to meet
the "producer / consumer" model.

So it is really weird/wrong to have a HW design where the MSI
infrastructure is shared across many devices.

Jason

  reply	other threads:[~2022-10-12 14:38 UTC|newest]

Thread overview: 113+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-03 12:26 [RFC PATCH 0/2] add support for CDX bus MSI domain Nipun Gupta
2022-08-03 12:26 ` [RFC PATCH 1/2] irqchip: cdx-bus: add cdx-MSI domain with gic-its domain as parent Nipun Gupta
2022-08-03 12:33   ` Greg KH
2022-08-03 12:37     ` Gupta, Nipun
2022-08-04  8:49   ` Marc Zyngier
2022-08-04  9:18     ` Gupta, Nipun
     [not found]       ` <87mtckwaxa.wl-maz@kernel.org>
2022-08-04 12:11         ` Gupta, Nipun
2022-08-03 12:26 ` [RFC PATCH 2/2] driver core: add compatible string in sysfs for platform devices Nipun Gupta
2022-08-03 12:31   ` Greg KH
2022-08-03 12:46     ` Gupta, Nipun
2022-08-03 14:16 ` [RFC PATCH 0/2] add support for CDX bus MSI domain Robin Murphy
2022-08-04  4:23   ` Gupta, Nipun
2022-08-17 16:00   ` Jason Gunthorpe
2022-08-17 15:05 ` [RFC PATCH v2 0/6] add support for CDX bus controller Nipun Gupta
2022-08-17 15:05   ` [RFC PATCH v2 1/6] Documentation: DT: Add entry for CDX controller Nipun Gupta
2022-08-18  9:54     ` Krzysztof Kozlowski
2022-08-18  9:59       ` Krzysztof Kozlowski
2022-09-05 14:05       ` Gupta, Nipun
2022-09-06  6:55         ` Krzysztof Kozlowski
2022-09-06  7:03           ` Gupta, Nipun
2022-09-06  7:20             ` Krzysztof Kozlowski
2022-08-17 15:05   ` [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver Nipun Gupta
2022-08-17 15:32     ` Greg KH
2022-08-17 15:46       ` Marc Zyngier
2022-08-22 13:21       ` Gupta, Nipun
2022-08-22 13:29         ` Greg KH
2022-08-24  8:50           ` Gupta, Nipun
2022-08-24 12:11             ` Greg KH
2022-08-24 23:31               ` Jason Gunthorpe
2022-08-25 18:38                 ` Saravana Kannan
2022-08-25 19:57                   ` Robin Murphy
2022-08-26  0:08                     ` Jason Gunthorpe
2022-08-29  4:49                       ` Gupta, Nipun
2022-08-29  4:49                     ` Gupta, Nipun
2022-08-29 15:31                       ` Jason Gunthorpe
2022-08-30  7:06                         ` Gupta, Nipun
2022-08-30 11:25                           ` Robin Murphy
2022-08-30 13:01                           ` Jason Gunthorpe
2022-08-30 13:12                             ` Gupta, Nipun
2022-08-17 15:05   ` [RFC PATCH v2 3/6] bus/cdx: add cdx-MSI domain with gic-its domain as parent Nipun Gupta
2022-08-17 15:33     ` Greg KH
2022-08-17 15:05   ` [RFC PATCH v2 4/6] bus/cdx: add rescan and reset support Nipun Gupta
2022-08-17 15:05   ` [RFC PATCH v2 5/6] vfio: platform: reset: add reset for cdx devices Nipun Gupta
2022-08-17 15:05   ` [RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices Nipun Gupta
2022-08-17 15:30     ` Greg KH
2022-08-17 16:04       ` Saravana Kannan
2022-09-05 13:54         ` Gupta, Nipun
2022-09-06 13:47 ` [RFC PATCH v3 0/7] add support for CDX bus Nipun Gupta
2022-09-06 13:47   ` [RFC PATCH v3 1/7] dt-bindings: bus: add CDX bus device tree bindings Nipun Gupta
2022-09-06 17:46     ` Rob Herring
2022-09-07  3:13       ` Gupta, Nipun
2022-09-08 10:51         ` Krzysztof Kozlowski
2022-09-06 13:47   ` [RFC PATCH v3 2/7] bus/cdx: add the cdx bus driver Nipun Gupta
2022-09-07  0:32     ` Saravana Kannan
2022-09-07  3:21       ` Gupta, Nipun
2022-09-07 18:06         ` Saravana Kannan
2022-09-07 12:32     ` Greg KH
2022-09-08 13:29       ` Gupta, Nipun
2022-09-06 13:47   ` [RFC PATCH v3 3/7] iommu/arm-smmu-v3: support ops registration for CDX bus Nipun Gupta
2022-09-07  0:10     ` Saravana Kannan
2022-09-07  3:17       ` Gupta, Nipun
2022-09-07  8:27         ` Robin Murphy
2022-09-07 18:24           ` Saravana Kannan
2022-09-07 20:40             ` Robin Murphy
2022-09-08  0:14               ` Saravana Kannan
2022-09-06 13:47   ` [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its domain as parent Nipun Gupta
2022-09-06 17:19     ` Jason Gunthorpe
2022-09-07 11:17       ` Marc Zyngier
2022-09-07 11:33         ` Robin Murphy
2022-09-07 12:14           ` Marc Zyngier
2022-09-07 11:35         ` Radovanovic, Aleksandar
     [not found]           ` <87illzuzyw.wl-maz@kernel.org>
2022-09-07 13:18             ` Radovanovic, Aleksandar
     [not found]               ` <87edwmuw4f.wl-maz@kernel.org>
2022-09-08  9:51                 ` Radovanovic, Aleksandar
2022-09-08 11:49                   ` Robin Murphy
2022-09-07 13:18     ` Marc Zyngier
2022-09-08 14:13       ` Gupta, Nipun
     [not found]         ` <87a67aueg7.wl-maz@kernel.org>
2022-09-09  6:32           ` Gupta, Nipun
2022-10-12 10:04       ` Gupta, Nipun
2022-10-12 10:34         ` Radovanovic, Aleksandar
2022-10-12 13:02           ` Jason Gunthorpe
2022-10-12 13:37             ` Radovanovic, Aleksandar
2022-10-12 14:38               ` Jason Gunthorpe [this message]
2022-10-12 15:09                 ` Radovanovic, Aleksandar
2022-10-13 12:43                   ` Jason Gunthorpe
2022-10-14 11:18                     ` Radovanovic, Aleksandar
2022-10-14 11:54                       ` gregkh
2022-10-14 12:13                         ` Radovanovic, Aleksandar
2022-10-14 13:46                           ` gregkh
2022-10-14 13:58                       ` Jason Gunthorpe
2022-09-06 13:47   ` [RFC PATCH v3 5/7] bus/cdx: add bus and device attributes Nipun Gupta
2022-09-06 13:48   ` [RFC PATCH v3 6/7] vfio/cdx: add support for CDX bus Nipun Gupta
2022-09-06 17:20     ` Jason Gunthorpe
2022-09-06 17:23       ` Gupta, Nipun
2022-09-06 13:48   ` [RFC PATCH v3 7/7] vfio/cdx: add interrupt support Nipun Gupta
2022-10-14  4:40 ` [RFC PATCH v4 0/8] add support for CDX bus Nipun Gupta
2022-10-14  4:40   ` [RFC PATCH v4 1/8] dt-bindings: bus: add CDX bus device tree bindings Nipun Gupta
2022-10-14 14:17     ` Rob Herring
2022-10-17 10:18       ` Gupta, Nipun
2022-10-14  4:40   ` [RFC PATCH v4 2/8] bus/cdx: add the cdx bus driver Nipun Gupta
2022-10-14  7:15     ` Greg KH
2022-10-14  8:12       ` Gupta, Nipun
2022-10-14  7:18     ` Greg KH
2022-10-14  8:20       ` Gupta, Nipun
2022-10-14  4:40   ` [RFC PATCH v4 3/8] iommu/arm-smmu-v3: support ops registration for CDX bus Nipun Gupta
2022-10-14  4:51     ` Gupta, Nipun
2022-10-14  4:40   ` [RFC PATCH v4 4/8] bux/cdx: support dma configuration for CDX devices Nipun Gupta
2022-10-14  4:40   ` [RFC PATCH v4 5/8] bus/cdx: add bus and device attributes Nipun Gupta
2022-10-14  4:40   ` [RFC PATCH v4 6/8] irq/msi: use implicit msi domain for alloc and free Nipun Gupta
2022-10-14  4:40   ` [RFC PATCH v4 7/8] bus/cdx: add cdx-MSI domain with gic-its domain as parent Nipun Gupta
2022-11-17 19:10     ` Thomas Gleixner
2022-10-14  4:40   ` [RFC PATCH v4 8/8] bus/cdx: add cdx controller Nipun Gupta
2022-10-14 14:10   ` [RFC PATCH v4 0/8] add support for CDX bus Rob Herring
2022-10-17 10:08     ` Gupta, Nipun

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