[PATCH] 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.

To dump the final region, manually issue a note_page() call with address
BIT(ia_bits) (end of guest IPA space) and level == -1 to trigger a level
change after the last region. Additionally treat level == -1 as a last
flushing note_page() call and avoid dumping the name of the next marker
for this case.

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 | 8 +++++---
 arch/arm64/mm/ptdump.c  | 5 +++--
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index c9140e22abcf..4096e4a92fae 100644
--- a/arch/arm64/kvm/ptdump.c
+++ b/arch/arm64/kvm/ptdump.c
@@ -155,11 +155,13 @@ static int kvm_ptdump_guest_show(struct seq_file *m, void *unused)
 		.seq		= m,
 	};
 
-	write_lock(&kvm->mmu_lock);
+	guard(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(&st->parser_state.ptdump, BIT(mmu->pgt->ia_bits), -1, 0);
 
-	return ret;
+	return 0;
 }
 
 static int kvm_ptdump_guest_open(struct inode *m, struct file *file)
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index ab9899ca1e5f..fed4e4407e0e 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -194,6 +194,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 	struct ptdump_pg_state *st = container_of(pt_st, struct ptdump_pg_state, ptdump);
 	struct ptdump_pg_level *pg_level = st->pg_level;
 	static const char units[] = "KMGTPE";
+	bool flush = level == -1;
 	ptdesc_t prot = 0;
 
 	/* check if the current level has been folded dynamically */
@@ -234,7 +235,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 				  pg_level[st->level].num);
 		pt_dump_seq_puts(st->seq, "\n");
 
-		if (addr >= st->marker[1].start_address) {
+		if (addr >= st->marker[1].start_address && !flush) {
 			st->marker++;
 			pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 		}
@@ -244,7 +245,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 		st->level = level;
 	}
 
-	if (addr >= st->marker[1].start_address) {
+	if (addr >= st->marker[1].start_address && !flush) {
 		st->marker++;
 		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 	}
-- 
2.43.0