Nouveau - Jun 2023 - [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling

On Mon, May 22, 2023 at 10:37:09AM +0200, Juergen Gross
wrote:
> In normal cases PCI passthrough in PV guests requires to start the guest
> with e820_host=1. So it should be rather easy to limit allocating the
> 64MB in PV guests to the cases where the memory map has non-RAM regions
> especially in the first 1MB of the memory.
>
> This will cover even hotplug cases. The only case not covered would be a
> guest started with e820_host=1 even if no PCI passthrough was planned.
> But this should be rather rare (at least I hope so).
So is this an ACK for the patch and can we go ahead with it?

(I'd still like to merge swiotlb-xen into swiotlb eventually, but it's
probably not going to happen this merge window)

On 07.06.23 15:12, Christoph Hellwig wrote:
> On Mon, May 22, 2023 at 10:37:09AM +0200, Juergen Gross wrote:
>> In normal cases PCI passthrough in PV guests requires to start the
guest
>> with e820_host=1. So it should be rather easy to limit allocating the
>> 64MB in PV guests to the cases where the memory map has non-RAM regions
>> especially in the first 1MB of the memory.
>>
>> This will cover even hotplug cases. The only case not covered would be
a
>> guest started with e820_host=1 even if no PCI passthrough was planned.
>> But this should be rather rare (at least I hope so).
> 
> So is this an ACK for the patch and can we go ahead with it?
As long as above mentioned check of the E820 map is done, yes.

If you want I can send a diff to be folded into your patch on Monday.
> 
> (I'd still like to merge swiotlb-xen into swiotlb eventually, but
it's
> probably not going to happen this merge window)
Would be nice.


Juergen
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