Messages in this thread | | | Date | Wed, 2 Aug 2023 17:29:56 +0200 | Subject | Re: [PATCH v2 3/8] kvm: explicitly set FOLL_HONOR_NUMA_FAULT in hva_to_pfn_slow() | From | David Hildenbrand <> |
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On 02.08.23 17:27, Mel Gorman wrote: > 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@redhat.com> > > Seems sane but I don't know KVM well enough to know if this is the only > relevant case so didn't ack.
Makes sense, some careful eyes from KVM people would be appreciated.
At least from kvm_main.c POV, I'm pretty confident that that's it.
-- Cheers,
David / dhildenb
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