From: Robin Murphy <robin.murphy@arm.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
Kevin Tian <kevin.tian@intel.com>,
Chaitanya Kulkarni <kch@nvidia.com>,
Ashok Raj <ashok.raj@intel.com>,
kvm@vger.kernel.org, rafael@kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Cornelia Huck <cohuck@redhat.com>,
linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
iommu@lists.linux-foundation.org,
Jacob jun Pan <jacob.jun.pan@intel.com>,
linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
Will Deacon <will@kernel.org>,
Diana Craciun <diana.craciun@oss.nxp.com>
Subject: Re: [PATCH 02/11] driver core: Set DMA ownership during driver bind/unbind
Date: Mon, 15 Nov 2021 18:35:37 +0000 [thread overview]
Message-ID: <cc9878ae-df49-950c-f4f8-2e6ba545079b@arm.com> (raw)
In-Reply-To: <20211115155613.GA2388278@nvidia.com>
On 2021-11-15 15:56, Jason Gunthorpe via iommu wrote:
> On Mon, Nov 15, 2021 at 03:37:18PM +0000, Robin Murphy wrote:
>
>> IOMMUs, and possibly even fewer of them support VFIO, so I'm in full
>> agreement with Greg and Christoph that this absolutely warrants being scoped
>> per-bus. I mean, we literally already have infrastructure to prevent drivers
>> binding if the IOMMU/DMA configuration is broken or not ready yet; why would
>> we want a totally different mechanism to prevent driver binding when the
>> only difference is that that configuration *is* ready and working to the
>> point that someone's already claimed it for other purposes?
>
> I see, that does make sense
>
> I see these implementations:
>
> drivers/amba/bus.c: .dma_configure = platform_dma_configure,
> drivers/base/platform.c: .dma_configure = platform_dma_configure,
> drivers/bus/fsl-mc/fsl-mc-bus.c: .dma_configure = fsl_mc_dma_configure,
> drivers/pci/pci-driver.c: .dma_configure = pci_dma_configure,
> drivers/gpu/host1x/bus.c: .dma_configure = host1x_dma_configure,
>
> Other than host1x they all work with VFIO.
>
> Also, there is no bus->dma_unconfigure() which would be needed to
> restore the device as well.
Not if we reduce the notion of "ownership" down to
"dev->iommu_group->domain != dev->iommu_group->default_domain", which
I'm becoming increasingly convinced is all we actually need here.
> So, would you rather see duplicated code into the 4 drivers, and a new
> bus op to 'unconfigure dma'
The .dma_configure flow is unavoidably a bit boilerplatey already, so
personally I'd go for having the implementations call back into a common
check, similarly to their current flow. That also leaves room for the
bus code to further refine the outcome based on what it might know,
which I can particularly imagine for cleverer buses like fsl-mc and
host1x which can have lots of inside knowledge about how their devices
may interact.
Robin.
> Or, a 'dev_configure_dma()' function that is roughly:
>
> if (dev->bus->dma_configure) {
> ret = dev->bus->dma_configure(dev);
> if (ret)
> return ret;
> if (!drv->suppress_auto_claim_dma_owner) {
> ret = iommu_device_set_dma_owner(dev, DMA_OWNER_KERNEL,
> NULL);
> if (ret)
> ret;
> }
> }
>
> And a pair'd undo.
>
> This is nice because we can enforce dev->bus->dma_configure when doing
> a user bind so everything holds together safely without relying on
> each bus_type to properly implement security.
>
> Jason
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>
next prev parent reply other threads:[~2021-11-15 18:38 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 2:05 [PATCH 00/11] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu
2021-11-15 2:05 ` [PATCH 01/11] iommu: Add device dma ownership set/release interfaces Lu Baolu
2021-11-15 13:14 ` Christoph Hellwig
2021-11-16 1:57 ` Lu Baolu
2021-11-16 13:46 ` Jason Gunthorpe
2021-11-17 5:22 ` Lu Baolu
2021-11-17 13:35 ` Jason Gunthorpe
2021-11-18 1:12 ` Lu Baolu
2021-11-18 14:10 ` Jason Gunthorpe
2021-11-18 2:39 ` Tian, Kevin
2021-11-18 13:33 ` Jason Gunthorpe
2021-11-19 5:44 ` Tian, Kevin
2021-11-19 11:14 ` Lu Baolu
2021-11-19 15:06 ` Jörg Rödel
2021-11-19 15:43 ` Jason Gunthorpe
2021-11-20 11:16 ` Lu Baolu
2021-11-19 12:56 ` Jason Gunthorpe
2021-11-15 20:38 ` Bjorn Helgaas
2021-11-16 1:52 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 02/11] driver core: Set DMA ownership during driver bind/unbind Lu Baolu
2021-11-15 6:59 ` Greg Kroah-Hartman
2021-11-15 13:20 ` Christoph Hellwig
2021-11-15 13:38 ` Jason Gunthorpe
2021-11-15 13:19 ` Christoph Hellwig
2021-11-15 13:24 ` Jason Gunthorpe
2021-11-15 15:37 ` Robin Murphy
2021-11-15 15:56 ` Jason Gunthorpe
2021-11-15 18:15 ` Christoph Hellwig
2021-11-15 18:35 ` Robin Murphy [this message]
2021-11-15 19:39 ` Jason Gunthorpe
2021-11-15 2:05 ` [PATCH 03/11] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming Lu Baolu
2021-11-15 13:21 ` Christoph Hellwig
2021-11-15 13:31 ` Jason Gunthorpe
2021-11-15 15:14 ` Robin Murphy
2021-11-15 16:17 ` Jason Gunthorpe
2021-11-15 17:54 ` Robin Murphy
2021-11-15 18:19 ` Christoph Hellwig
2021-11-15 18:44 ` Robin Murphy
2021-11-15 19:22 ` Jason Gunthorpe
2021-11-15 20:58 ` Robin Murphy
2021-11-15 21:19 ` Jason Gunthorpe
2021-11-15 20:48 ` Bjorn Helgaas
2021-11-15 22:17 ` Bjorn Helgaas
2021-11-16 6:05 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 04/11] PCI: portdrv: " Lu Baolu
2021-11-15 20:44 ` Bjorn Helgaas
2021-11-16 7:24 ` Lu Baolu
2021-11-16 20:22 ` Bjorn Helgaas
2021-11-16 20:48 ` Jason Gunthorpe
2021-11-15 2:05 ` [PATCH 05/11] iommu: Add security context management for assigned devices Lu Baolu
2021-11-15 13:22 ` Christoph Hellwig
2021-11-16 7:25 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 06/11] iommu: Expose group variants of dma ownership interfaces Lu Baolu
2021-11-15 13:27 ` Christoph Hellwig
2021-11-16 9:42 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 07/11] vfio: Use DMA_OWNER_USER to declaim passthrough devices Lu Baolu
2021-11-15 2:05 ` [PATCH 08/11] vfio: Remove use of vfio_group_viable() Lu Baolu
2021-11-15 2:05 ` [PATCH 09/11] vfio: Delete the unbound_list Lu Baolu
2021-11-15 2:05 ` [PATCH 10/11] vfio: Remove iommu group notifier Lu Baolu
2021-11-15 2:05 ` [PATCH 11/11] iommu: Remove iommu group changes notifier Lu Baolu
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