Hi Peter,

On 09/13/2018 09:55 AM, Peter Xu wrote:
There are two callers for vtd_sync_shadow_page_table_range(), one
provided a valid context entry and one not.  Move that fetching
operation into the caller vtd_sync_shadow_page_table() where we need to
fetch the context entry.

Meanwhile, we should handle VTD_FR_CONTEXT_ENTRY_P properly when
synchronizing shadow page tables.  Having invalid context entry there is
perfectly valid when we move a device out of an existing domain.  When
that happens, instead of posting an error we invalidate the whole region.

Without this patch, QEMU will crash if we do these steps:

(1) start QEMU with VT-d IOMMU and two 10G NICs (ixgbe)
(2) bind the NICs with vfio-pci in the guest
(3) start testpmd with the NICs applied
(4) stop testpmd
(5) rebind the NIC back to ixgbe kernel driver

The patch should fix it.

Reported-by: Pei Zhang<pezh...@redhat.com>
Tested-by: Pei Zhang<pezh...@redhat.com>
CC: Pei Zhang<pezh...@redhat.com>
CC: Alex Williamson<alex.william...@redhat.com>
CC: Jason Wang<jasow...@redhat.com>
CC: Maxime Coquelin<maxime.coque...@redhat.com>
CC: Michael S. Tsirkin<m...@redhat.com>
CC: QEMU Stable<qemu-sta...@nongnu.org>
Fixes:https://bugzilla.redhat.com/show_bug.cgi?id=1627272

It seems like a regression as it wasn't reported earlier, isn't it?
If it is, do you know what is the faulty commit?

Signed-off-by: Peter Xu<pet...@redhat.com>
---
  hw/i386/intel_iommu.c | 54 ++++++++++++++++++++++++++-----------------
  1 file changed, 33 insertions(+), 21 deletions(-)

Other than that, the patch looks good to me.
FWIW:
Acked-by: Maxime Coquelin <maxime.coque...@redhat.com>

Thanks,
Maxime

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