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From: Joerg Roedel <joro@8bytes.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Stuart Yoder <stuyoder@gmail.com>,
	rafael@kernel.org, David Airlie <airlied@linux.ie>,
	linux-pci@vger.kernel.org,
	Thierry Reding <thierry.reding@gmail.com>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	Dmitry Osipenko <digetx@gmail.com>, Will Deacon <will@kernel.org>,
	Ashok Raj <ashok.raj@intel.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Christoph Hellwig <hch@infradead.org>,
	Kevin Tian <kevin.tian@intel.com>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	kvm@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Cornelia Huck <cohuck@redhat.com>,
	linux-kernel@vger.kernel.org, Li Yang <leoyang.li@nxp.com>,
	iommu@lists.linux-foundation.org,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v1 3/8] iommu: Extend iommu_at[de]tach_device() for multi-device groups
Date: Tue, 15 Feb 2022 09:58:13 +0100	[thread overview]
Message-ID: <YgtrJVI9wGMFdPWk@8bytes.org> (raw)
In-Reply-To: <20220214154626.GF4160@nvidia.com>

On Mon, Feb 14, 2022 at 11:46:26AM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 14, 2022 at 03:18:31PM +0000, Robin Murphy wrote:
> 
> > Arguably, iommu_attach_device() could be renamed something like
> > iommu_attach_group_for_dev(), since that's effectively the semantic that all
> > the existing API users want anyway (even VFIO at the high level - the group
> > is the means for the user to assign their GPU/NIC/whatever device to their
> > process, not the end in itself). That's just a lot more churn.
> 
> Right

Okay, good point. I can live with an iommu_attach_group_for_dev()
interface, it is still better than making iommu_attach_device() silently
operate on whole groups.

> VFIO needs them because its uAPI is tied, but even so we keep talking
> about ways to narrow the amount of group API it consumes.
> 
> We should not set the recommended/good kAPI based on VFIOs uAPI
> design.

Agree here too. The current way groups are implemented can be turned
into a VFIO specific interface to keep its semantics and kABI. But the
IOMMU core code still needs the concept of alias groups.

Regards,

	Joerg
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
	Stuart Yoder <stuyoder@gmail.com>,
	rafael@kernel.org, David Airlie <airlied@linux.ie>,
	linux-pci@vger.kernel.org,
	Thierry Reding <thierry.reding@gmail.com>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	Dmitry Osipenko <digetx@gmail.com>, Will Deacon <will@kernel.org>,
	Ashok Raj <ashok.raj@intel.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Christoph Hellwig <hch@infradead.org>,
	Kevin Tian <kevin.tian@intel.com>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	kvm@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Cornelia Huck <cohuck@redhat.com>,
	linux-kernel@vger.kernel.org, Li Yang <leoyang.li@nxp.com>,
	iommu@lists.linux-foundation.org,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH v1 3/8] iommu: Extend iommu_at[de]tach_device() for multi-device groups
Date: Tue, 15 Feb 2022 09:58:13 +0100	[thread overview]
Message-ID: <YgtrJVI9wGMFdPWk@8bytes.org> (raw)
In-Reply-To: <20220214154626.GF4160@nvidia.com>

On Mon, Feb 14, 2022 at 11:46:26AM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 14, 2022 at 03:18:31PM +0000, Robin Murphy wrote:
> 
> > Arguably, iommu_attach_device() could be renamed something like
> > iommu_attach_group_for_dev(), since that's effectively the semantic that all
> > the existing API users want anyway (even VFIO at the high level - the group
> > is the means for the user to assign their GPU/NIC/whatever device to their
> > process, not the end in itself). That's just a lot more churn.
> 
> Right

Okay, good point. I can live with an iommu_attach_group_for_dev()
interface, it is still better than making iommu_attach_device() silently
operate on whole groups.

> VFIO needs them because its uAPI is tied, but even so we keep talking
> about ways to narrow the amount of group API it consumes.
> 
> We should not set the recommended/good kAPI based on VFIOs uAPI
> design.

Agree here too. The current way groups are implemented can be turned
into a VFIO specific interface to keep its semantics and kABI. But the
IOMMU core code still needs the concept of alias groups.

Regards,

	Joerg

  reply	other threads:[~2022-02-15  8:58 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-06  2:20 [PATCH v1 0/8] Scrap iommu_attach/detach_group() interfaces Lu Baolu
2022-01-06  2:20 ` Lu Baolu
2022-01-06  2:20 ` [PATCH v1 1/8] iommu: Add iommu_group_replace_domain() Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06 17:06   ` Jason Gunthorpe via iommu
2022-01-06 17:06     ` Jason Gunthorpe
2022-01-07  0:26     ` Lu Baolu
2022-01-07  0:26       ` Lu Baolu
2022-02-14 12:09   ` Robin Murphy
2022-02-14 12:09     ` Robin Murphy
2022-02-14 12:45     ` Jason Gunthorpe via iommu
2022-02-14 12:45       ` Jason Gunthorpe
2022-02-14 14:10       ` Robin Murphy
2022-02-14 14:10         ` Robin Murphy
2022-02-14 14:56         ` Jason Gunthorpe via iommu
2022-02-14 14:56           ` Jason Gunthorpe
2022-02-14 16:38           ` Robin Murphy
2022-02-14 16:38             ` Robin Murphy
2022-02-14 17:25             ` Jason Gunthorpe via iommu
2022-02-14 17:25               ` Jason Gunthorpe
2022-01-06  2:20 ` [PATCH v1 2/8] vfio/type1: Use iommu_group_replace_domain() Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06  2:20 ` [PATCH v1 3/8] iommu: Extend iommu_at[de]tach_device() for multi-device groups Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06 17:22   ` Jason Gunthorpe via iommu
2022-01-06 17:22     ` Jason Gunthorpe
2022-01-07  1:14     ` Lu Baolu
2022-01-07  1:14       ` Lu Baolu
2022-01-07  1:19       ` Jason Gunthorpe via iommu
2022-01-07  1:19         ` Jason Gunthorpe
2022-02-14 11:39   ` Joerg Roedel
2022-02-14 11:39     ` Joerg Roedel
2022-02-14 13:03     ` Jason Gunthorpe via iommu
2022-02-14 13:03       ` Jason Gunthorpe
2022-02-14 14:39       ` Joerg Roedel
2022-02-14 14:39         ` Joerg Roedel
2022-02-14 15:18         ` Robin Murphy
2022-02-14 15:18           ` Robin Murphy
2022-02-14 15:46           ` Jason Gunthorpe via iommu
2022-02-14 15:46             ` Jason Gunthorpe
2022-02-15  8:58             ` Joerg Roedel [this message]
2022-02-15  8:58               ` Joerg Roedel
2022-02-15 13:47               ` Jason Gunthorpe via iommu
2022-02-15 13:47                 ` Jason Gunthorpe
2022-02-16  6:28                 ` Lu Baolu
2022-02-16  6:28                   ` Lu Baolu
2022-02-16 13:54                   ` Jason Gunthorpe via iommu
2022-02-16 13:54                     ` Jason Gunthorpe
2022-01-06  2:20 ` [PATCH v1 4/8] drm/tegra: Use iommu_attach/detatch_device() Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06  2:20 ` [PATCH v1 5/8] iommu/amd: Use iommu_attach/detach_device() Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06 14:33   ` Jason Gunthorpe via iommu
2022-01-06 14:33     ` Jason Gunthorpe
2022-01-07  0:23     ` Lu Baolu
2022-01-07  0:23       ` Lu Baolu
2022-02-14 11:27     ` Joerg Roedel
2022-02-14 11:27       ` Joerg Roedel
2022-02-14 13:15       ` Jason Gunthorpe via iommu
2022-02-14 13:15         ` Jason Gunthorpe
2022-02-14 13:40         ` Joerg Roedel
2022-02-14 13:40           ` Joerg Roedel
2022-02-14 14:02           ` Jason Gunthorpe via iommu
2022-02-14 14:02             ` Jason Gunthorpe
2022-02-14 14:23             ` Joerg Roedel
2022-02-14 14:23               ` Joerg Roedel
2022-02-14 15:00               ` Jason Gunthorpe via iommu
2022-02-14 15:00                 ` Jason Gunthorpe
2022-02-15  9:11                 ` Joerg Roedel
2022-02-15  9:11                   ` Joerg Roedel
2022-02-15 13:02                   ` Robin Murphy
2022-02-15 13:02                     ` Robin Murphy
2022-02-15 14:37                   ` Jason Gunthorpe via iommu
2022-02-15 14:37                     ` Jason Gunthorpe
2022-01-06  2:20 ` [PATCH v1 6/8] gpu/host1x: " Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06 15:35   ` Jason Gunthorpe via iommu
2022-01-06 15:35     ` Jason Gunthorpe
2022-01-07  0:35     ` Lu Baolu
2022-01-07  0:35       ` Lu Baolu
2022-01-07  0:48       ` Jason Gunthorpe via iommu
2022-01-07  0:48         ` Jason Gunthorpe
2022-01-07  1:19         ` Lu Baolu
2022-01-07  1:19           ` Lu Baolu
2022-01-06  2:20 ` [PATCH v1 7/8] media: staging: media: tegra-vde: " Lu Baolu
2022-01-06  2:20   ` Lu Baolu
2022-01-06  2:20 ` [PATCH v1 8/8] iommu: Remove iommu_attach/detach_group() Lu Baolu
2022-01-06  2:20   ` Lu Baolu

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