Paolo Bonzini <pbonzini@xxxxxxxxxx> writes:
> The .change_pte() MMU notifier callback was intended as an
> optimization. The original point of it was that KSM could tell KVM to flip
> its secondary PTE to a new location without having to first zap it. At
> the time there was also an .invalidate_page() callback; both of them were
> *not* bracketed by calls to mmu_notifier_invalidate_range_{start,end}(),
> and .invalidate_page() also doubled as a fallback implementation of
> .change_pte().
>
> Later on, however, both callbacks were changed to occur within an
> invalidate_range_start/end() block.
>
> In the case of .change_pte(), commit 6bdb913f0a70 ("mm: wrap calls to
> set_pte_at_notify with invalidate_range_start and invalidate_range_end",
> 2012-10-09) did so to remove the fallback from .invalidate_page() to
> .change_pte() and allow sleepable .invalidate_page() hooks.
>
> This however made KVM's usage of the .change_pte() callback completely
> moot, because KVM unmaps the sPTEs during .invalidate_range_start()
> and therefore .change_pte() has no hope of finding a sPTE to change.
> Drop the generic KVM code that dispatches to kvm_set_spte_gfn(), as
> well as all the architecture specific implementations.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> 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 ---
LGTM.
Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (powerpc)
cheers
