On 7/30/24 22:21, Sean Christopherson wrote:
On Tue, Jul 30, 2024, Paolo Bonzini wrote:
On 7/27/24 01:52, Sean Christopherson wrote:
Now that KVM no longer relies on an ugly heuristic to find its struct page
references, i.e. now that KVM can't get false positives on VM_MIXEDMAP
pfns, remove KVM's hack to elevate the refcount for pfns that happen to
have a valid struct page. In addition to removing a long-standing wart
in KVM, this allows KVM to map non-refcounted struct page memory into the
guest, e.g. for exposing GPU TTM buffers to KVM guests.
Feel free to leave it to me for later, but there are more cleanups that
can be made, given how simple kvm_resolve_pfn() is now:
I'll revisit kvm_resolve_pfn(), Maxim also wasn't a fan of a similar helper that
existed in v11.
FWIW kvm_resolve_pfn() is totally fine as an intermediate step. Just
food for thought for possible follow-ups.
Also, check_user_page_hwpoison() should not be needed anymore, probably
not since commit 234b239bea39 ("kvm: Faults which trigger IO release the
mmap_sem", 2014-09-24) removed get_user_pages_fast() from hva_to_pfn_slow().
Ha, I *knew* this sounded familiar. Past me apparently came to the same
conclusion[*], though I wrongly suspected a memory leak and promptly forgot to
ever send a patch. I'll tack one on this time around.
As you prefer.
Paolo
