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intel_iommu: support snoop control

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SC is required for some kernel features like vhost-vDPA. So this patch
implements basic SC feature. The idea is pretty simple, for software
emulated DMA it would be always coherent. In this case we can simple
advertise ECAP_SC bit. For VFIO and vhost, thing will be more much
complicated, so this patch simply fail the IOMMU notifier
registration.

In the future, we may want to have a dedicated notifiers flag or
similar mechanism to demonstrate the coherency so VFIO could advertise
that if it has VFIO_DMA_CC_IOMMU, for vhost kernel backend we don't
need that since it's a software backend.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220214060346.72455-1-jasowang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Jason Wang 2022-02-14 14:03:46 +08:00 • committed by Michael S. Tsirkin
parent b1f030a0a2
commit b8ffd7d671
3 changed files with 15 additions and 1 deletions
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1
include/hw/i386/intel_iommu.h
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@ -228,6 +228,7 @@ struct IntelIOMMUState {
bool caching_mode; /* RO - is cap CM enabled? */
bool scalable_mode; /* RO - is Scalable Mode supported? */
bool snoop_control; /* RO - is SNP filed supported? */
dma_addr_t root; /* Current root table pointer */
bool root_scalable; /* Type of root table (scalable or not) */