The .change_pte() MMU notifier callback was intended as an optimization
and for this reason it was initially called without a surrounding
mmu_notifier_invalidate_range_{start,end}() pair. It was only ever
implemented by KVM (which was also the original user of MMU notifiers)
and the rules on when to call set_pte_at_notify() rather than set_pte_at()
have always been pretty obscure.
It may seem a miracle that it has never caused any hard to trigger
bugs, but there's a good reason for that: KVM's implementation has
been nonfunctional for a good part of its existence. Already in
2012, commit 6bdb913f0a70 ("mm: wrap calls to set_pte_at_notify with
invalidate_range_start and invalidate_range_end", 2012-10-09) changed the
.change_pte() callback to occur within an invalidate_range_start/end()
pair; and because KVM unmaps the sPTEs during .invalidate_range_start(),
.change_pte() has no hope of finding a sPTE to change.
Therefore, all the code for .change_pte() can be removed from both KVM
and mm/, and set_pte_at_notify() can be replaced with just set_pte_at().
Please review! Also feel free to take the KVM patches through the mm
tree, as I don't expect any conflicts.
Thanks,
Paolo
Paolo Bonzini (4):
KVM: delete .change_pte MMU notifier callback
KVM: remove unused argument of kvm_handle_hva_range()
mmu_notifier: remove the .change_pte() callback
mm: replace set_pte_at_notify() with just set_pte_at()
arch/arm64/kvm/mmu.c | 34 -----------------
arch/loongarch/include/asm/kvm_host.h | 1 -
arch/loongarch/kvm/mmu.c | 32 ----------------
arch/mips/kvm/mmu.c | 30 ---------------
arch/powerpc/include/asm/kvm_ppc.h | 1 -
arch/powerpc/kvm/book3s.c | 5 ---
arch/powerpc/kvm/book3s.h | 1 -
arch/powerpc/kvm/book3s_64_mmu_hv.c | 12 ------
arch/powerpc/kvm/book3s_hv.c | 1 -
arch/powerpc/kvm/book3s_pr.c | 7 ----
arch/powerpc/kvm/e500_mmu_host.c | 6 ---
arch/riscv/kvm/mmu.c | 20 ----------
arch/x86/kvm/mmu/mmu.c | 54 +--------------------------
arch/x86/kvm/mmu/spte.c | 16 --------
arch/x86/kvm/mmu/spte.h | 2 -
arch/x86/kvm/mmu/tdp_mmu.c | 46 -----------------------
arch/x86/kvm/mmu/tdp_mmu.h | 1 -
include/linux/kvm_host.h | 2 -
include/linux/mmu_notifier.h | 44 ----------------------
include/trace/events/kvm.h | 15 --------
kernel/events/uprobes.c | 5 +--
mm/ksm.c | 4 +-
mm/memory.c | 7 +---
mm/migrate_device.c | 8 +---
mm/mmu_notifier.c | 17 ---------
virt/kvm/kvm_main.c | 50 +------------------------
26 files changed, 10 insertions(+), 411 deletions(-)
--
2.43.0
