Re: [PATCH 2/7] guest_memfd: Introduce an object to manage the guest-memfd with RamDiscardManager

David Hildenbrand
2025-01-24T18:17:22Z

> Definitely not suggesting to install an invalid pointer anywhere. The
> mapped pointer will still be valid for gmem for example, but the fault
> isn't. We need to differenciate two things (1) virtual address mapping,
> then (2) permission and accesses on the folios / pages of the mapping.
> Here I think it's okay if the host pointer is correctly mapped.
>
> For your private MMIO use case, my question is if there's no host pointer
> to be mapped anyway, then what's the benefit to make the MR to be ram=on?
> Can we simply make it a normal IO memory region? The only benefit of a
> ram=on MR is, IMHO, being able to be accessed as RAM-like. If there's no
> host pointer at all, I don't yet understand how that helps private MMIO
> from working.

Same here.

--
Cheers,

David / dhildenb