Re: [Intel-gfx] [PATCH 2/6] KVM: mmu: also return page from gfn_to_pfn

Nicholas Piggin
2021-06-24T09:58:05Z

Excerpts from Paolo Bonzini's message of June 24, 2021 7:42 pm:
> On 24/06/21 10:52, Nicholas Piggin wrote:
>>> For now, wrap all calls to gfn_to_pfn functions in the new helper
>>> function. Callers which don't need the page struct will be updated in
>>> follow-up patches.
>> Hmm. You mean callers that do need the page will be updated? Normally
>> if there will be leftover users that don't need the struct page then
>> you would go the other way and keep the old call the same, and add a new
>> one (gfn_to_pfn_page) just for those that need it.
>
> Needing kvm_pfn_page_unwrap is a sign that something might be buggy, so
> it's a good idea to move the short name to the common case and the ugly
> kvm_pfn_page_unwrap(gfn_to_pfn(...)) for the weird one. In fact I'm not
> sure there should be any kvm_pfn_page_unwrap in the end.

If all callers were updated that is one thing, but from the changelog
it sounds like that would not happen and there would be some gfn_to_pfn
users left over.

But yes in the end you would either need to make gfn_to_pfn never return
a page found via follow_pte, or change all callers to the new way. If
the plan is for the latter then I guess that's fine.

Thanks,
Nick