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From: Lu Baolu <baolu.lu@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>, Bjorn Helgaas <helgaas@kernel.org>
Cc: baolu.lu@linux.intel.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Joerg Roedel <joro@8bytes.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Christoph Hellwig <hch@infradead.org>,
	Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	rafael@kernel.org, Diana Craciun <diana.craciun@oss.nxp.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Eric Auger <eric.auger@redhat.com>, Liu Yi L <yi.l.liu@intel.com>,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Stuart Yoder <stuyoder@gmail.com>,
	Laurentiu Tudor <laurentiu.tudor@nxp.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Li Yang <leoyang.li@nxp.com>, Dmitry Osipenko <digetx@gmail.com>,
	iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 03/13] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming
Date: Fri, 31 Dec 2021 09:58:11 +0800	[thread overview]
Message-ID: <9daec0aa-b58f-93b3-c8bb-b67ec6d84596@linux.intel.com> (raw)
In-Reply-To: <5eb8650c-432f-bf06-c63d-6320199ef894@linux.intel.com>

On 12/31/21 9:10 AM, Lu Baolu wrote:
> 
> On 12/31/21 8:40 AM, Jason Gunthorpe wrote:
>> On Thu, Dec 30, 2021 at 04:24:14PM -0600, Bjorn Helgaas wrote:
>>
>>> I was speculating that maybe the DMA ownership claiming must be done
>>> *before* the driver's .probe() method?
>>
>> This is correct.
>>
>>> If DMA ownership could be claimed by the .probe() method, we
>>> wouldn't need the new flag in struct device_driver.
>>
>> The other requirement is that every existing driver must claim
>> ownership, so pushing this into the device driver's probe op would
>> require revising almost every driver in Linux...
>>
>> In effect the new flag indicates if the driver will do the DMA
>> ownership claim in it's probe, or should use the default claim the
>> core code does.
>>
>> In almost every case a driver should do a claim. A driver like
>> pci-stub, or a bridge, that doesn't actually operate MMIO on the
>> device would be the exception.
> 
> We still need to call iommu_device_use_dma_api() in bus dma_configure()
> callback. But we can call iommu_device_unuse_dma_api() in the .probe()
> of vfio (and vfio-approved) drivers, so that we don't need the new flag
> anymore.

Oh, wait. I didn't think about the hot-plug case. If we call
iommu_device_use_dma_api() in bus dma_configure() anyway, we can't bind
any (no matter vfio or none-vfio) driver to a device if it's group has
already been assigned to user space. It seems that we can't omit this
flag.

Best regards,
baolu

  reply	other threads:[~2021-12-31  1:58 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-17  6:36 [PATCH v4 00/13] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu
2021-12-17  6:36 ` [PATCH v4 01/13] iommu: Add device dma ownership set/release interfaces Lu Baolu
2021-12-17  6:36 ` [PATCH v4 02/13] driver core: Set DMA ownership during driver bind/unbind Lu Baolu
2021-12-22 12:47   ` Greg Kroah-Hartman
2021-12-22 17:52     ` Jason Gunthorpe
2021-12-23  2:08     ` Lu Baolu
2021-12-23  3:02     ` Lu Baolu
2021-12-23  7:13       ` Greg Kroah-Hartman
2021-12-23  7:23         ` Lu Baolu
2021-12-31  0:36           ` Jason Gunthorpe
2021-12-17  6:36 ` [PATCH v4 03/13] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming Lu Baolu
2021-12-29 20:42   ` Bjorn Helgaas
2021-12-30  5:34     ` Lu Baolu
2021-12-30 22:24       ` Bjorn Helgaas
2021-12-31  0:40         ` Jason Gunthorpe
2021-12-31  1:10           ` Lu Baolu
2021-12-31  1:58             ` Lu Baolu [this message]
2022-01-03 19:53             ` Jason Gunthorpe
2022-01-04  1:54               ` Lu Baolu
2021-12-31  1:06         ` Lu Baolu
2021-12-17  6:36 ` [PATCH v4 04/13] PCI: portdrv: " Lu Baolu
2021-12-29 21:16   ` Bjorn Helgaas
2021-12-30  5:49     ` Lu Baolu
2021-12-17  6:37 ` [PATCH v4 05/13] iommu: Add security context management for assigned devices Lu Baolu
2021-12-17  6:37 ` [PATCH v4 06/13] iommu: Expose group variants of dma ownership interfaces Lu Baolu
2021-12-17  6:37 ` [PATCH v4 07/13] iommu: Add iommu_at[de]tach_device_shared() for multi-device groups Lu Baolu
2021-12-21 16:50   ` Robin Murphy
2021-12-21 18:46     ` Jason Gunthorpe
2021-12-22  4:22       ` Lu Baolu
2021-12-22  4:25         ` Lu Baolu
2021-12-22 20:26       ` Robin Murphy
2021-12-23  0:57         ` Jason Gunthorpe
2021-12-23  5:53           ` Lu Baolu
2021-12-23 14:03             ` Jason Gunthorpe
2021-12-24  1:30               ` Lu Baolu
2021-12-24  2:50                 ` Jason Gunthorpe
2021-12-24  6:44                   ` Lu Baolu
2022-01-04  1:53                   ` Lu Baolu
2021-12-24  3:19         ` Lu Baolu
2021-12-24 14:24           ` Jason Gunthorpe
2021-12-17  6:37 ` [PATCH v4 08/13] vfio: Set DMA USER ownership for VFIO devices Lu Baolu
2021-12-17  6:37 ` [PATCH v4 09/13] vfio: Remove use of vfio_group_viable() Lu Baolu
2021-12-17  6:37 ` [PATCH v4 10/13] vfio: Delete the unbound_list Lu Baolu
2021-12-17  6:37 ` [PATCH v4 11/13] vfio: Remove iommu group notifier Lu Baolu
2021-12-17  6:37 ` [PATCH v4 12/13] iommu: Remove iommu group changes notifier Lu Baolu
2021-12-17  6:37 ` [PATCH v4 13/13] drm/tegra: Use the iommu dma_owner mechanism Lu Baolu
2022-01-04  5:23 ` [PATCH v4 00/13] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu

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