On 26.05.2021 19:33, Sean Christopherson wrote:

On Sun, May 16, 2021, Maciej S. Szmigiero wrote:

quoted

From: "Maciej S. Szmigiero" <redacted>

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 <redacted>
---
  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.

That's a good idea, will do.

Thanks,
Maciej