Re: [Qemu-devel] [PATCH] intel_iommu: handle invalid ce for shadow sync

[Maxime Coquelin]

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<address@hidden>
> Tested-by: Pei Zhang<address@hidden>
> CC: Pei Zhang<address@hidden>
> CC: Alex Williamson<address@hidden>
> CC: Jason Wang<address@hidden>
> CC: Maxime Coquelin<address@hidden>
> CC: Michael S. Tsirkin<address@hidden>
> CC: QEMU Stable<address@hidden>
> 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<address@hidden>
> ---
>   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 <address@hidden>

Thanks,
Maxime