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charset="gb2312" Content-Transfer-Encoding: quoted-printable

hi paolo,


>2) you're addin= g a check for the host, but the bug applies to all hosts.
>If there is a bug = on x86 hardware emulation, it should be fixed even
>when emulating x86= from ARM.  It should also apply to all CPU vendors.  &nbs= p;      


What is the progress of handling this bug ? 

If the processing is more complicated, can we temporarily remove flatvie= w_simplify()?


hi Alex,


>the issue here = is that the delete+add passes are racing against an
>assigned device's = DMA


Please help comment how to solve this problem.


Best regards

Felixcui-oc 


=B7=A2=BC=FE=C8=CB: Paolo= Bonzini <pbonzini@redhat.com>
=B7=A2=CB=CD=CA=B1=BC=E4: 2020=C4=EA10=D4=C216=C8=D5 19:42:29
=CA=D5=BC=FE=C8=CB: FelixCui-oc; Richard Henderson; Eduardo Habkost;= Alex Williamson
=B3=AD=CB=CD: qemu-devel@nongnu.org; RockCui-oc; Tony W Wang-oc; Cob= eChen-oc; Alex Williamson
=D6=F7=CC=E2: Re: [PATCH 1/1] Skip flatview_simplify() for cpu vendo= r zhaoxin
 
On 16/10/20 13:29, FelixCuioc wrote:
> The issue here is that an assinged EHCI device accesses
> an adjacent mapping between the delete and add phases
> of the VFIO MemoryListener.
> We want to skip flatview_simplify() is to prevent EHCI
> device IOVA mappings from being unmapped.

Hi,

there is indeed a bug, but I have already explained last month
(https://mail.gnu.org/archive/html/qemu-devel/2020-09/msg01279.html= )
that this patch is conceptually wrong:

1) you're adding host_get_vendor conditioned on compiling the x86
emulator, so you are breaking compilation on non-x86 machines.

2) you're adding a check for the host, but the bug applies to all hosts.  If there is a bug on x86 hardware emulation, it should be fixed even<= br> when emulating x86 from ARM.  It should also apply to all CPU vendors.=

Alex, the issue here is that the delete+add passes are racing against a= n
assigned device's DMA. For KVM we were thinking of changing the whole
memory map with a single ioctl, but that's much easier because KVM
builds its page tables lazily. It would be possible for the IOMMU too
but it would require a relatively complicated comparison of the old and
new memory maps in the kernel.

Paolo

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