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Subject[PATCH] KVM: x86/mmu: Speed up slot_rmap_walk_next for sparsely populated rmaps
From
Avoid calling handlers on empty rmap entries and skip to the next non
empty rmap entry.

Empty rmap entries are noop in handlers.

Signed-off-by: Vipin Sharma <vipinsh@google.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Change-Id: I8abf0f4d82a2aae4c5d58b80bcc17ffc30785ffc
---
arch/x86/kvm/mmu/mmu.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 51671cb34fb6..f296340803ba 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1499,11 +1499,14 @@ static bool slot_rmap_walk_okay(struct slot_rmap_walk_iterator *iterator)
return !!iterator->rmap;
}

-static void slot_rmap_walk_next(struct slot_rmap_walk_iterator *iterator)
+static noinline void
+slot_rmap_walk_next(struct slot_rmap_walk_iterator *iterator)
{
- if (++iterator->rmap <= iterator->end_rmap) {
+ while (++iterator->rmap <= iterator->end_rmap) {
iterator->gfn += (1UL << KVM_HPAGE_GFN_SHIFT(iterator->level));
- return;
+
+ if (iterator->rmap->val)
+ return;
}

if (++iterator->level > iterator->end_level) {
base-commit: c9b8fecddb5bb4b67e351bbaeaa648a6f7456912
--
2.35.1.1021.g381101b075-goog

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