On 7/27/24 01:51, Sean Christopherson wrote:

arm64 folks, the first two patches are bug fixes, but I have very low
confidence that they are correct and/or desirable.  If they are more or
less correct, I can post them separately if that'd make life easier.  I
included them here to avoid conflicts, and because I'm pretty sure how
KVM deals with MTE tags vs. dirty logging will impact what APIs KVM needs
to provide to arch code.

On to the series...  The TL;DR is that I would like to get input on two
things:

  1. Marking folios dirty/accessed only on the intial stage-2 page fault
  2. The new APIs for faulting, prefetching, and doing "lookups" on pfns

Wow!

Splitting out prefetching makes a lot of sense, as it's the only one 
with npages > 1 and it doesn't need all the complexity of hva_to_pfn().

I've left a comment on the lookup API, which is probably the only one 
that can be simplified further.

The faulting API looks good as a first iteration.  Code-wise, 
kvm_resolve_pfn() is probably unnecessary at the end of the series but I 
can see why you had to restrain yourself and declare it done. :)

An interesting evolution of the API could be to pass a struct 
kvm_follow_pfn pointer to {,__}kvm_faultin_pfn() and __gfn_to_page() 
(the "constructors"); and on the other side to 
kvm_release_faultin_page() and kvm_release_page_*().  The struct 
kvm_follow_pfn could be embedded in the (x86) kvm_page_fault and 
(generic) kvm_host_map structs.  But certainly not as part of this 
already huge work.

Paolo