Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking

Paolo Bonzini
2019-12-04T11:05:00Z

On 04/12/19 11:38, Jason Wang wrote:
>>
>> +    entry = &ring->dirty_gfns[ring->dirty_index & (ring->size - 1)];
>> +    entry->slot = slot;
>> +    entry->offset = offset;
>
>
> Haven't gone through the whole series, sorry if it was a silly question
> but I wonder things like this will suffer from similar issue on
> virtually tagged archs as mentioned in [1].

There is no new infrastructure to track the dirty pages---it's just a
different way to pass them to userspace.

> Is this better to allocate the ring from userspace and set to KVM
> instead? Then we can use copy_to/from_user() friends (a little bit slow
> on recent CPUs).

Yeah, I don't think that would be better than mmap.

Paolo

> [1] https://lkml.org/lkml/2019/4/9/5