From: Alex Williamson <alex.williamson@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
Christoph Hellwig <hch@lst.de>,
Lu Baolu <baolu.lu@linux.intel.com>,
Christian Benvenuti <benve@cisco.com>,
Cornelia Huck <cohuck@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Jason Wang <jasowang@redhat.com>, Joerg Roedel <joro@8bytes.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
Matthew Rosato <mjrosato@linux.ibm.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Nelson Escobar <neescoba@cisco.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Rob Clark <robdclark@gmail.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY with dev_is_dma_coherent()
Date: Thu, 7 Apr 2022 16:37:37 -0600 [thread overview]
Message-ID: <20220407163737.2a7ccd7a.alex.williamson@redhat.com> (raw)
In-Reply-To: <20220407152331.GN2120790@nvidia.com>
On Thu, 7 Apr 2022 12:23:31 -0300
Jason Gunthorpe <jgg@nvidia.com> wrote:
> On Thu, Apr 07, 2022 at 04:17:11PM +0100, Robin Murphy wrote:
>
> > For the specific case of overriding PCIe No Snoop (which is more problematic
> > from an Arm SMMU PoV) when assigning to a VM, would that not be easier
> > solved by just having vfio-pci clear the "Enable No Snoop" control bit in
> > the endpoint's PCIe capability?
>
> Ideally.
>
> That was rediscussed recently, apparently there are non-compliant
> devices and drivers that just ignore the bit.
>
> Presumably this is why x86 had to move to an IOMMU enforced feature..
I considered this option when implementing the current solution, but
ultimately I didn't have confidence in being able to prevent drivers
from using device specific means to effect the change anyway. GPUs
especially have various back channels to config space. Thanks,
Alex
next prev parent reply other threads:[~2022-04-07 22:38 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-05 16:15 [PATCH 0/5] Make the iommu driver no-snoop block feature consistent Jason Gunthorpe
2022-04-05 16:16 ` [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY with dev_is_dma_coherent() Jason Gunthorpe
2022-04-06 5:30 ` Christoph Hellwig
2022-04-06 12:07 ` Jason Gunthorpe
2022-04-06 13:51 ` Christoph Hellwig
2022-04-06 14:14 ` Jason Gunthorpe
2022-04-06 15:47 ` Christoph Hellwig
2022-04-06 15:48 ` Jason Gunthorpe
2022-04-06 15:48 ` Robin Murphy
2022-04-06 13:56 ` Robin Murphy
2022-04-06 14:24 ` Jason Gunthorpe
2022-04-06 15:18 ` Jason Gunthorpe
2022-04-06 15:50 ` Christoph Hellwig
2022-04-06 16:06 ` Jason Gunthorpe
2022-04-06 16:10 ` Christoph Hellwig
2022-04-06 17:17 ` Jason Gunthorpe
2022-04-07 7:18 ` Tian, Kevin
2022-04-07 13:59 ` Jason Gunthorpe
2022-04-07 15:17 ` Robin Murphy
2022-04-07 15:23 ` Jason Gunthorpe
2022-04-07 22:37 ` Alex Williamson [this message]
2022-04-07 15:31 ` Christoph Hellwig
2022-04-07 8:53 ` Niklas Schnelle
2022-04-05 16:16 ` [PATCH 2/5] vfio: Require that devices support DMA cache coherence Jason Gunthorpe
2022-04-05 19:10 ` Alex Williamson
2022-04-05 19:29 ` Jason Gunthorpe
2022-04-06 7:02 ` Tian, Kevin
2022-04-07 14:53 ` Jason Gunthorpe
2022-04-05 16:16 ` [PATCH 3/5] iommu: Introduce the domain op enforce_cache_coherency() Jason Gunthorpe
2022-04-05 19:50 ` Alex Williamson
2022-04-05 22:57 ` Jason Gunthorpe
2022-04-05 23:31 ` Tian, Kevin
2022-04-06 0:08 ` Tian, Kevin
2022-04-06 7:09 ` Tian, Kevin
2022-04-06 12:27 ` Jason Gunthorpe
2022-04-05 16:16 ` [PATCH 4/5] vfio: Move the Intel no-snoop control off of IOMMU_CACHE Jason Gunthorpe
2022-04-05 16:16 ` [PATCH 5/5] iommu: Delete IOMMU_CAP_CACHE_COHERENCY Jason Gunthorpe
2022-04-06 6:52 ` [PATCH 0/5] Make the iommu driver no-snoop block feature consistent Tian, Kevin
2022-04-07 14:56 ` Jason Gunthorpe
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