On Sun, May 16, 2021, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@xxxxxxxxxx>
>
> Introduce a memslots gfn upper bound operation and use it to optimize
> kvm_zap_gfn_range().
> This way this handler can do a quick lookup for intersecting gfns and won't
> have to do a linear scan of the whole memslot set.
>
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu.c | 41 ++++++++++++++++++++++++++++++++++++++--
> include/linux/kvm_host.h | 22 +++++++++++++++++++++
> 2 files changed, 61 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 7222b552d139..f23398cf0316 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5490,14 +5490,51 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> int i;
> bool flush = false;
>
> + if (gfn_end == gfn_start || WARN_ON(gfn_end < gfn_start))
> + return;
> +
> write_lock(&kvm->mmu_lock);
> for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> - int ctr;
> + int idxactive;
> + struct rb_node *node;
>
> slots = __kvm_memslots(kvm, i);
> - kvm_for_each_memslot(memslot, ctr, slots) {
> + idxactive = kvm_memslots_idx(slots);
> +
> + /*
> + * Find the slot with the lowest gfn that can possibly intersect with
> + * the range, so we'll ideally have slot start <= range start
> + */
> + node = kvm_memslots_gfn_upper_bound(slots, gfn_start);
> + if (node) {
> + struct rb_node *pnode;
> +
> + /*
> + * A NULL previous node means that the very first slot
> + * already has a higher start gfn.
> + * In this case slot start > range start.
> + */
> + pnode = rb_prev(node);
> + if (pnode)
> + node = pnode;
> + } else {
> + /* a NULL node below means no slots */
> + node = rb_last(&slots->gfn_tree);
> + }
> +
> + for ( ; node; node = rb_next(node)) {
> gfn_t start, end;
Can this be abstracted into something like:
kvm_for_each_memslot_in_gfn_range(...) {
}
and share that implementation with kvm_check_memslot_overlap() in the next patch?
I really don't think arch code should be poking into gfn_tree, and ideally arch
code wouldn't even be aware that gfn_tree exists.
> + memslot = container_of(node, struct kvm_memory_slot,
> + gfn_node[idxactive]);
> +
> + /*
> + * If this slot starts beyond or at the end of the range so does
> + * every next one
> + */
> + if (memslot->base_gfn >= gfn_start + gfn_end)
> + break;
> +
> start = max(gfn_start, memslot->base_gfn);
> end = min(gfn_end, memslot->base_gfn + memslot->npages);
> if (start >= end)
