On Tue, Aug 01, 2023 at 02:48:39PM +0200, David Hildenbrand wrote: > KVM is *the* case we know that really wants to honor NUMA hinting falls. > As we want to stop setting FOLL_HONOR_NUMA_FAULT implicitly, set > FOLL_HONOR_NUMA_FAULT whenever we might obtain pages on behalf of a VCPU > to map them into a secondary MMU, and add a comment why. > > Do that unconditionally in hva_to_pfn_slow() when calling > get_user_pages_unlocked(). > > kvmppc_book3s_instantiate_page(), hva_to_pfn_fast() and > gfn_to_page_many_atomic() are similarly used to map pages into a > secondary MMU. However, FOLL_WRITE and get_user_page_fast_only() always > implicitly honor NUMA hinting faults -- as documented for > FOLL_HONOR_NUMA_FAULT -- so we can limit this change to a single location > for now. > > Don't set it in check_user_page_hwpoison(), where we really only want to > check if the mapped page is HW-poisoned. > > We won't set it for other KVM users of get_user_pages()/pin_user_pages() > * arch/powerpc/kvm/book3s_64_mmu_hv.c: not used to map pages into a > secondary MMU. > * arch/powerpc/kvm/e500_mmu.c: only used on shared TLB pages with userspace > * arch/s390/kvm/*: s390x only supports a single NUMA node either way > * arch/x86/kvm/svm/sev.c: not used to map pages into a secondary MMU. > > This is a preparation for making FOLL_HONOR_NUMA_FAULT no longer > implicitly be set by get_user_pages() and friends. > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Seems sane but I don't know KVM well enough to know if this is the only relevant case so didn't ack. -- Mel Gorman SUSE Labs
