[PATCH v3 0/2] arm64: ptdump flush fixes

[PATCH v3 0/2] arm64: ptdump flush fixes

[Wei-Lin Chang]

Hi,

This series fixes two problems around ptdumps:

1. note_page_flush(), which flushes out the last row of ptdumps, does
   not account for address spaces that have IA < 64. Other than making
   the last region extremely huge, the attributes of the last region
   within the address spaces appear to extend all the way to 1 << 64.

2. KVM/arm64's stage-2 ptdump missed calling note_page_flush().

To address Will's comment [1], I have created an end_address field for
struct ptdump_pg_state, and initialized it with the end address of the
ptdumps. It follows the same convention as the last range->end:
exclusive end, except for the case where the address space ends at
1 << 64. In that case it is set as ULONG_MAX.

Caching the end address avoids duplicating the range iteration in
note_page_flush(), at the cost of duplicating state in ptdump_pg_state.

Series is based on v7.2-rc5.

* Changes from v2:

  - Instead of scanning ptdump_state.range[] to find the end address,
    cache the end address in a new field end_address when we initialize
    struct ptdump_pg_state.

  - Adjust KVM's struct ptdump_pg_state initialization so it uses
    end_address instead of ptdump_state.range[].

  - Collected Reviewed-by and Tested-by from Dev, thanks!

  - v2: https://lore.kernel.org/r/20260724185431.2990395-1-weilin.chang@arm.com/

* Changes from v1:

  - Instead of manually calling note_page() for flushing, fix
    note_page_flush() so that it ends the ptdump at the end of the
    address space.

  - Changed the start address of the second marker to ULONG_MAX for KVM
    ptdump, so we don't output extra marker names, and advance past the
    end of the marker array.

  - v1: https://lore.kernel.org/r/20260717231233.2299068-1-weilin.chang@arm.com/

Thanks!

[1]: https://lore.kernel.org/r/anXFo-igVdqrCogQ@willie-the-truck/

Wei-Lin Chang (2):
  arm64: ptdump: Make note_page_flush() range aware
  KVM: arm64: ptdump: Flush the last region

 arch/arm64/include/asm/ptdump.h |  2 ++
 arch/arm64/kvm/ptdump.c         | 11 +++++++----
 arch/arm64/mm/ptdump.c          | 14 +++++++++++++-
 3 files changed, 22 insertions(+), 5 deletions(-)

-- 
2.43.0

[PATCH v3 1/2] arm64: ptdump: Make note_page_flush() range aware

[Wei-Lin Chang]

note_page_flush() calls note_page() with addr == 0 and level == -1 to
dump the last row of a ptdump. addr == 0 (1 << 64 wrapped around)
renders a huge region with enormous size for address spaces with
IA bits < 64. For example the stage-2 page tables and the EFI runtime
page table.

More importantly, the last region of the address space and everything
after the address space up to 1 << 64 are merged into one row of
output. If the last region within the address space is valid, it will
appear to remain valid up to 1 << 64 with the same attributes.

Currently only the EFI runtime ptdump is affected by this, but KVM will
soon fix its stage-2 ptdump by using note_page_flush(). Here is an
example of an EFI runtime ptdump (last row):

0x0000008000000000-0x0000000000000000   17179868672G PGD

With this patch:

0x0000008000000000-0x0001000000000000      261632G PGD

To fix this, cache the end address of a ptdump in ptdump_pg_state so
note_page_flush() can call the final note_page() with the correct end
address.

Fixes: 9d80448ac92b ("efi/arm64: Add debugfs node to dump UEFI runtime page tables")
Signed-off-by: Wei-Lin Chang <weilin.chang@arm.com>
---
 arch/arm64/include/asm/ptdump.h |  2 ++
 arch/arm64/mm/ptdump.c          | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
index 5b374a6ab34a..1b743de7d89e 100644
--- a/arch/arm64/include/asm/ptdump.h
+++ b/arch/arm64/include/asm/ptdump.h
@@ -52,6 +52,8 @@ struct ptdump_pg_state {
 	const struct addr_marker *marker;
 	const struct mm_struct *mm;
 	unsigned long start_address;
+	/* exclusive end, ULONG_MAX represents an end at 1 << 64 */
+	unsigned long end_address;
 	int level;
 	ptval_t current_prot;
 	bool check_wx;
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 1c20144700d7..eab400e744d9 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -278,9 +278,19 @@ void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
 
 void note_page_flush(struct ptdump_state *pt_st)
 {
+	struct ptdump_pg_state *st = container_of(pt_st, struct ptdump_pg_state, ptdump);
+	unsigned long end = st->end_address;
 	pte_t pte_zero = {0};
 
-	note_page(pt_st, 0, -1, pte_val(pte_zero));
+	/*
+	 * Address spaces that end at 1 << 64 have end_address == ULONG_MAX,
+	 * but note_page() expects the exclusive end. In this case adjust end
+	 * to the wraparound value 0.
+	 */
+	if (end == ULONG_MAX)
+		end = 0;
+
+	note_page(pt_st, end, -1, pte_val(pte_zero));
 }
 
 static void arm64_ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)
@@ -303,6 +313,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
 		.marker = info->markers,
 		.mm = info->mm,
 		.pg_level = &kernel_pg_levels[0],
+		.end_address = end,
 		.level = -1,
 		.ptdump = {
 			.note_page_pte = note_page_pte,
@@ -344,6 +355,7 @@ bool ptdump_check_wx(void)
 			{ -1, NULL},
 		},
 		.pg_level = &kernel_pg_levels[0],
+		.end_address = ~0UL,
 		.level = -1,
 		.check_wx = true,
 		.ptdump = {
-- 
2.43.0

[PATCH v3 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()
uses ptdump_pg_state.end_address to call the final note_page(), so also
provide the end address.

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@kernel.org>
Closes: https://lore.kernel.org/kvmarm/20260630122758.891011F00A3A@smtp.kernel.org/
Reviewed-by: Dev Jain <dev.jain@arm.com>
Tested-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Wei-Lin Chang <weilin.chang@arm.com>
---
 arch/arm64/kvm/ptdump.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index c9140e22abcf..69899797dbad 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 +148,21 @@ 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],
+		.end_address	= BIT(mmu->pgt->ia_bits),
 		.level		= -1,
 		.pg_level	= &st->level[0],
 		.seq		= m,
 	};
 
-	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

Re: [PATCH v3 1/2] arm64: ptdump: Make note_page_flush() range aware

[Marc Zyngier]

On Fri, 14 Aug 2026 23:24:57 +0100,
Wei-Lin Chang <weilin.chang@arm.com> wrote:
> 
> note_page_flush() calls note_page() with addr == 0 and level == -1 to
> dump the last row of a ptdump. addr == 0 (1 << 64 wrapped around)
> renders a huge region with enormous size for address spaces with
> IA bits < 64. For example the stage-2 page tables and the EFI runtime
> page table.
> 
> More importantly, the last region of the address space and everything
> after the address space up to 1 << 64 are merged into one row of
> output. If the last region within the address space is valid, it will
> appear to remain valid up to 1 << 64 with the same attributes.
> 
> Currently only the EFI runtime ptdump is affected by this, but KVM will
> soon fix its stage-2 ptdump by using note_page_flush(). Here is an
> example of an EFI runtime ptdump (last row):
> 
> 0x0000008000000000-0x0000000000000000   17179868672G PGD
> 
> With this patch:
> 
> 0x0000008000000000-0x0001000000000000      261632G PGD
> 
> To fix this, cache the end address of a ptdump in ptdump_pg_state so
> note_page_flush() can call the final note_page() with the correct end
> address.
> 
> Fixes: 9d80448ac92b ("efi/arm64: Add debugfs node to dump UEFI runtime page tables")
> Signed-off-by: Wei-Lin Chang <weilin.chang@arm.com>
> ---
>  arch/arm64/include/asm/ptdump.h |  2 ++
>  arch/arm64/mm/ptdump.c          | 14 +++++++++++++-
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 5b374a6ab34a..1b743de7d89e 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -52,6 +52,8 @@ struct ptdump_pg_state {
>  	const struct addr_marker *marker;
>  	const struct mm_struct *mm;
>  	unsigned long start_address;
> +	/* exclusive end, ULONG_MAX represents an end at 1 << 64 */
> +	unsigned long end_address;
>  	int level;
>  	ptval_t current_prot;
>  	bool check_wx;
> diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
> index 1c20144700d7..eab400e744d9 100644
> --- a/arch/arm64/mm/ptdump.c
> +++ b/arch/arm64/mm/ptdump.c
> @@ -278,9 +278,19 @@ void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
>  
>  void note_page_flush(struct ptdump_state *pt_st)
>  {
> +	struct ptdump_pg_state *st = container_of(pt_st, struct ptdump_pg_state, ptdump);
> +	unsigned long end = st->end_address;
>  	pte_t pte_zero = {0};
>  
> -	note_page(pt_st, 0, -1, pte_val(pte_zero));
> +	/*
> +	 * Address spaces that end at 1 << 64 have end_address == ULONG_MAX,
> +	 * but note_page() expects the exclusive end. In this case adjust end
> +	 * to the wraparound value 0.
> +	 */
> +	if (end == ULONG_MAX)
> +		end = 0;
> +
> +	note_page(pt_st, end, -1, pte_val(pte_zero));
>  }
>  
>  static void arm64_ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)
> @@ -303,6 +313,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
>  		.marker = info->markers,
>  		.mm = info->mm,
>  		.pg_level = &kernel_pg_levels[0],
> +		.end_address = end,
>  		.level = -1,
>  		.ptdump = {
>  			.note_page_pte = note_page_pte,
> @@ -344,6 +355,7 @@ bool ptdump_check_wx(void)
>  			{ -1, NULL},
>  		},
>  		.pg_level = &kernel_pg_levels[0],
> +		.end_address = ~0UL,

nit: shouldn't this be ULONG_MAX instead? Yes, this is the same thing,
but it doesn't hurt to match the documentation.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.