From: Alex Williamson <alex.williamson@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Nelson Escobar <neescoba@cisco.com>,
Matthew Rosato <mjrosato@linux.ibm.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
Joerg Roedel <joro@8bytes.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
"linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Cornelia Huck <cohuck@redhat.com>,
Rob Clark <robdclark@gmail.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Christian Benvenuti <benve@cisco.com>,
David Woodhouse <dwmw2@infradead.org>,
Lu Baolu <baolu.lu@linux.intel.com>
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
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next prev parent reply other threads:[~2022-04-07 22:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <0-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com>
[not found] ` <2-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com>
2022-04-05 19:10 ` [PATCH 2/5] vfio: Require that devices support DMA cache coherence Alex Williamson
[not found] ` <20220405192916.GT2120790@nvidia.com>
2022-04-06 7:02 ` Tian, Kevin
[not found] ` <1-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com>
2022-04-06 5:30 ` [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY with dev_is_dma_coherent() Christoph Hellwig
[not found] ` <20220406120730.GA2120790@nvidia.com>
2022-04-06 13:51 ` Christoph Hellwig
[not found] ` <20220406141446.GE2120790@nvidia.com>
2022-04-06 15:47 ` Christoph Hellwig
2022-04-06 15:48 ` Robin Murphy
2022-04-06 13:56 ` Robin Murphy
[not found] ` <20220406142432.GF2120790@nvidia.com>
[not found] ` <20220406151823.GG2120790@nvidia.com>
2022-04-06 15:50 ` Christoph Hellwig
[not found] ` <20220406160623.GI2120790@nvidia.com>
2022-04-06 16:10 ` Christoph Hellwig
[not found] ` <20220406171729.GJ2120790@nvidia.com>
2022-04-07 7:18 ` Tian, Kevin
[not found] ` <20220407135946.GM2120790@nvidia.com>
2022-04-07 15:17 ` Robin Murphy
2022-04-07 15:31 ` Christoph Hellwig
[not found] ` <20220407152331.GN2120790@nvidia.com>
2022-04-07 22:37 ` Alex Williamson [this message]
2022-04-06 6:52 ` [PATCH 0/5] Make the iommu driver no-snoop block feature consistent Tian, Kevin
[not found] ` <3-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com>
2022-04-05 19:50 ` [PATCH 3/5] iommu: Introduce the domain op enforce_cache_coherency() Alex Williamson
[not found] ` <20220405225739.GW2120790@nvidia.com>
2022-04-05 23:31 ` Tian, Kevin
2022-04-06 0:08 ` Tian, Kevin
2022-04-06 7:09 ` Tian, Kevin
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