[PATCH v2 09/13] KVM: arm64: Dirty-bitmap: avoid splitting previously split blocks

[Leonardo Bras]

If previous dirty-clean already split a block, then avoid calling the
split helper on that block again.

Signed-off-by: Leonardo Bras <leo.bras at arm.com>
---
 arch/arm64/kvm/dirty_bit.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/dirty_bit.c b/arch/arm64/kvm/dirty_bit.c
index d05af3de78be..6c928677ce12 100644
--- a/arch/arm64/kvm/dirty_bit.c
+++ b/arch/arm64/kvm/dirty_bit.c
@@ -153,20 +153,21 @@ int __kvm_arch_dirty_log_clear(struct kvm *kvm,
 			       bool *flush)
 {
 	int ret = 0;
 	int idx = 0;
 	unsigned long *dirty_bitmap = memslot->dirty_bitmap;
 	u64 *hw_entries;
 	const int entries_sz = PAGE_SIZE / sizeof(*hw_entries);
 	u64 ttwl;
 	u64 start, end;
 	gfn_t base_gfn;
+	gpa_t split_end = 0;
 
 	hw_entries = kmalloc_objs(u64, entries_sz, GFP_KERNEL);
 	if (!hw_entries)
 		return -ENOMEM;
 
 	ttwl = HDBSS_ENTRY_TTWL(KVM_PGTABLE_LAST_LEVEL);
 
 	if (log) {
 		start = log->first_page / BITS_PER_LONG;
 		end = start + DIV_ROUND_UP(log->num_pages, BITS_PER_LONG);
@@ -197,24 +198,28 @@ int __kvm_arch_dirty_log_clear(struct kvm *kvm,
 
 			mask = xchg(&dirty_bitmap[i], 0);
 			bitmap[i] = mask;
 		}
 
 		if (!mask)
 			continue;
 
 		offset = base_gfn + i * BITS_PER_LONG;
 
-		if (kvm_dirty_log_manual_protect_and_init_set(kvm))
-			kvm_mmu_split_huge_pages(kvm,
-						 gfn_to_gpa(offset + __ffs(mask)),
-						 gfn_to_gpa(offset + __fls(mask) + 1));
+		if (kvm_dirty_log_manual_protect_and_init_set(kvm) &&
+		    (offset + BITS_PER_LONG > split_end)) {
+			gpa_t start = gfn_to_gpa(offset + __ffs(mask));
+			gpa_t end = gfn_to_gpa(offset + __fls(mask) + 1);
+
+			kvm_mmu_split_huge_pages(kvm, start, end);
+			split_end = gpa_to_gfn(ALIGN_DOWN(end, PMD_SIZE) + PMD_SIZE - 1);
+		}
 
 		do {
 			idx = mask_to_hdbss(&mask, hw_entries, offset, ttwl, idx, entries_sz);
 			if (idx >= entries_sz) {
 				ret = dirty_bit_clear(kvm, hw_entries, idx);
 				*flush = *flush || ret > 0;
 				if (ret != idx) {
 					/* Save bits not converted back to bitmap */
 					atomic_long_or(mask, (atomic_long_t *)&dirty_bitmap[i]);
 					goto out_err;
-- 
2.54.0