[PATCH v2 2/2] KVM: arm64: ptdump: Flush the last region

[Wei-Lin Chang]

Currently the stage-2 ptdump calls note_page() at each leaf entry visit.
This simply misses the output of the last region, because note_page()
only dumps output when it detects a change in level/prot, or when the
walk enters a next marker section. The last region in the guest IPA
space with the same level/prot is not dumped since there is no change
after it.

Call note_page_flush() to dump the final region. note_page_flush()
expects ptdump_state.range[] to be initialized to the range of the
address space, so also do that.

Also change the second marker's start address to ULONG_MAX so we never
cross it. This avoids dumping redundant marker names (which are NULL),
and advancing beyond the end of the marker array.

Fixes: 7c4f73548ed1 ("KVM: arm64: Register ptdump with debugfs on guest creation")
Reported-by: Sashiko AI <sashiko-bot@xxxxxxxxxx>
Closes: https://lore.kernel.org/kvmarm/20260630122758.891011F00A3A@xxxxxxxxxxxxxxx/
Signed-off-by: Wei-Lin Chang <weilin.chang@xxxxxxx>
---
 arch/arm64/kvm/ptdump.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index c9140e22abcf..222577163d2b 100644
--- a/arch/arm64/kvm/ptdump.c
+++ b/arch/arm64/kvm/ptdump.c
@@ -130,7 +130,7 @@ static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm_s2_mmu
 	}
 
 	st->ipa_marker[0].name		= "Guest IPA";
-	st->ipa_marker[1].start_address = BIT(pgtable->ia_bits);
+	st->ipa_marker[1].start_address = ULONG_MAX;
 
 	st->mmu				= mmu;
 	return st;
@@ -148,18 +148,26 @@ static int kvm_ptdump_guest_show(struct seq_file *m, void *unused)
 		.flags	= KVM_PGTABLE_WALK_LEAF,
 	};
 
+	guard(write_lock)(&kvm->mmu_lock);
 	st->parser_state = (struct ptdump_pg_state) {
 		.marker		= &st->ipa_marker[0],
 		.level		= -1,
 		.pg_level	= &st->level[0],
 		.seq		= m,
+		.ptdump		= {
+			.range = (struct ptdump_range[]){
+				{0, BIT(mmu->pgt->ia_bits)},
+				{0, 0}
+			}
+		}
 	};
 
-	write_lock(&kvm->mmu_lock);
 	ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker);
-	write_unlock(&kvm->mmu_lock);
+	if (ret)
+		return ret;
+	note_page_flush(&st->parser_state.ptdump);
 
-	return ret;
+	return 0;
 }
 
 static int kvm_ptdump_guest_open(struct inode *m, struct file *file)
-- 
2.43.0