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intel_iommu: dma read/write draining support

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Support DMA read/write draining should be easy for existing VT-d
emulation since the emulation itself does not have any request queue
there so we don't need to do anything to flush the un-commited queue.
What we need to do is to declare the support.

These capabilities are required to pass Windows SVVP test program.  It
is verified that when with parameters "x-aw-bits=48,caching-mode=off"
we can pass the Windows SVVP test with this patch applied.  Otherwise
we'll fail with:

        IOMMU[0] - DWD (DMA write draining) not supported
        IOMMU[0] - DWD (DMA read draining) not supported
        Segment 0 has no DMA remapping capable IOMMU units

However since these bits are not declared support for QEMU<=3.1, we'll
need a compatibility bit for it and we turn this on by default only
for QEMU>=4.0.

Please refer to VT-d spec 6.5.4 for more information.

CC: Yu Wang <wyu@redhat.com>
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1654550
Signed-off-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:
Peter Xu 2018-12-17 15:31:12 +08:00 • committed by Michael S. Tsirkin
parent 095955b24d
commit ccc23bb08a
4 changed files with 13 additions and 0 deletions
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1
include/hw/i386/intel_iommu.h
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@ -245,6 +245,7 @@ struct IntelIOMMUState {
OnOffAuto intr_eim; /* Toggle for EIM cabability */
bool buggy_eim; /* Force buggy EIM unless eim=off */
uint8_t aw_bits; /* Host/IOVA address width (in bits) */
bool dma_drain; /* Whether DMA r/w draining enabled */
/*
* Protects IOMMU states in general. Currently it protects the