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| author | Jason Gunthorpe <jgg@nvidia.com> | 2022-04-11 18:16:06 +0300 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2022-04-28 18:24:57 +0300 |
| commit | 71cfafda9c9bd9812cdb62ddb94daf65a1af12c1 (patch) | |
| tree | f1bc4377a68f66b6da05adc92e2dabd9edb3c796 /include/linux/intel-iommu.h | |
| parent | 6043257b1de069fbb5a2a52d7211c0275bc8c0e0 (diff) | |
| download | linux-71cfafda9c9bd9812cdb62ddb94daf65a1af12c1.tar.xz | |
vfio: Move the Intel no-snoop control off of IOMMU_CACHE
IOMMU_CACHE means "normal DMA to this iommu_domain's IOVA should be cache
coherent" and is used by the DMA API. The definition allows for special
non-coherent DMA to exist - ie processing of the no-snoop flag in PCIe
TLPs - so long as this behavior is opt-in by the device driver.
The flag is mainly used by the DMA API to synchronize the IOMMU setting
with the expected cache behavior of the DMA master. eg based on
dev_is_dma_coherent() in some case.
For Intel IOMMU IOMMU_CACHE was redefined to mean 'force all DMA to be
cache coherent' which has the practical effect of causing the IOMMU to
ignore the no-snoop bit in a PCIe TLP.
x86 platforms are always IOMMU_CACHE, so Intel should ignore this flag.
Instead use the new domain op enforce_cache_coherency() which causes every
IOPTE created in the domain to have the no-snoop blocking behavior.
Reconfigure VFIO to always use IOMMU_CACHE and call
enforce_cache_coherency() to operate the special Intel behavior.
Remove the IOMMU_CACHE test from Intel IOMMU.
Ultimately VFIO plumbs the result of enforce_cache_coherency() back into
the x86 platform code through kvm_arch_register_noncoherent_dma() which
controls if the WBINVD instruction is available in the guest. No other
archs implement kvm_arch_register_noncoherent_dma() nor are there any
other known consumers of VFIO_DMA_CC_IOMMU that might be affected by the
user visible result change on non-x86 archs.
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v3-2cf356649677+a32-intel_no_snoop_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'include/linux/intel-iommu.h')
| -rw-r--r-- | include/linux/intel-iommu.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h index 4c2baf2446c2..72e5d7900e71 100644 --- a/include/linux/intel-iommu.h +++ b/include/linux/intel-iommu.h @@ -539,7 +539,6 @@ struct dmar_domain { u8 has_iotlb_device: 1; u8 iommu_coherency: 1; /* indicate coherency of iommu access */ - u8 iommu_snooping: 1; /* indicate snooping control feature */ u8 force_snooping : 1; /* Create IOPTEs with snoop control */ struct list_head devices; /* all devices' list */ |