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Re: [Qemu-devel] [PATCH] intel-iommu: send PSI always when notify_unmap
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH] intel-iommu: send PSI always when notify_unmap set |
Date: |
Wed, 18 Apr 2018 13:28:22 +0800 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Wed, Apr 18, 2018 at 12:51:21PM +0800, Peter Xu wrote:
> During IOVA page table walk, there is a special case when:
>
> - notify_unmap is set, meanwhile
> - entry is invalid
>
> In the past, we skip the entry always. This is not correct. We should
> send UNMAP notification to registered notifiers in this case. Otherwise
> some stall pages will still be mapped in the host even if L1 guest
> unmapped them already.
>
> Without this patch, nested device assignment to L2 guests might dump
> some errors like:
>
> qemu-system-x86_64: VFIO_MAP_DMA: -17
> qemu-system-x86_64: vfio_dma_map(0x557305420c30, 0xad000, 0x1000,
> 0x7f89a920d000) = -17 (File exists)
>
> To fix this, we need to apply this patch to L1 QEMU (L2 QEMU is not
> affected by this problem).
>
> Signed-off-by: Peter Xu <address@hidden>
This should really be 2.12 material, it fixes a real bug, but not sure
whether it's too late already. Michael, what do you think?
Thanks,
--
Peter Xu