Re: [Invitation] bi-weekly guest_memfd upstream call on 2024-11-14

[David Hildenbrand <david@redhat.com>]

On 24.12.24 05:21, Alexey Kardashevskiy wrote:
> On 14/11/24 13:27, Chao Gao wrote:
>>>> With in-place conversion, QEMU can map shared memory and supply the virtual
>>>> address to VFIO to set up DMA mappings. From this perspective, in-place
>>>> conversion doesn't change or require any changes to the way QEMU interacts
>>>> with VFIO. So, the key for device assignment remains updating DMA mappings
>>>> accordingly during shared/private conversions. It seems that whether in-place
>>>> conversion is in use (i.e., whether shared memory is managed by guest_memfd or
>>>> not) doesn't require big changes to that proposal. Not sure if anyone thinks
>>>> otherwise. We want to align with you on the direction for device assignment
>>>> support for guest_memfd.
>>>> (I set aside the idea of letting KVM manage the IOMMU page table in the above
>>>>     analysis because we probably won't get that support in the near future)
>>>
>>> Right. So devices would also only be to access "shared" memory.
>>
>> Yes, this is the situation without TDX-Connect support. Even when TDX-Connect
>> comes into play, devices will initially be attached in shared mode and later
>> converted to private mode. From this perspective, TDX-Connect will be built on
>> this shared device assignment proposal.
>>
>>>
>>>>
>>>> Could you please add this topic to the agenda?
>>>
>>> Will do. But I'm afraid the agenda for tomorrow is pretty packed, so we might
>>> not get to talk about it in more detail before the meeting in 2 weeks.
>>
>> Understood. is there any QEMU patch available for in-place conversion? we would
>> like to play with it and also do some experiments w/ assigned devices. This
>> might help us identify more potential issues for discussion.
> 
> 
> Have you found out if there are patches, somewhere? I am interested too.

I remember that so far only Kernel patches are available [1], I assume 
because Google focuses on other user space than QEMU. So I suspect the 
QEMU integration is still TBD.


[1] https://lkml.kernel.org/r/20241213164811.2006197-1-tabba@google.com

-- 
Cheers,

David / dhildenb