From: Jackie Liu <liu.yun@linux.dev>
To: akpm@linux-foundation.org
Cc: palmer@dabbelt.com, aou@eecs.berkeley.edu, glider@google.com,
dvyukov@google.com, elver@google.com, pjw@kernel.org,
alex@ghiti.fr, linux-riscv@lists.infradead.org,
linux-mm@kvack.org, kasan-dev@googlegroups.com
Subject: [PATCH 1/2] riscv: Recognize P4D leaves when splitting the linear mapping
Date: Fri, 30 Oct 2026 18:59:32 +0800 [thread overview]
Message-ID: <20261030105933.4180-2-liu.yun@linux.dev> (raw)
In-Reply-To: <20261030105933.4180-1-liu.yun@linux.dev>
From: Jackie Liu <liuyun01@kylinos.cn>
The linear mapping can contain P4D leaves on Sv57, but p4d_leaf() uses
the generic definition which always returns false. Splitting a partial
P4D range therefore treats the mapped physical memory as a PUD table
instead of allocating and populating that table.
Check the hardware leaf bits in the linear-map splitter. Only do so
when the PUD level is present: on Sv39 the folded P4D entry may contain
a PUD leaf, which must be handled by the PUD splitter.
Keep this check local to kernel mappings. Defining p4d_leaf() globally
would conflict with the GUP assertions that userspace P4D leaves are
unsupported.
Link: https://lore.kernel.org/all/sashiko-outbox-190189@kernel.org/
Fixes: 311cd2f6e253 ("riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge linear mappings")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
arch/riscv/mm/pageattr.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 5b3cf326455db..32834a09a8097 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -197,7 +197,8 @@ static int __split_linear_mapping_p4d(pgd_t *pgdp,
vaddr <= (vaddr & P4D_MASK) && end >= next)
continue;
- if (p4d_leaf(p4dp_get(p4dp))) {
+ /* p4d_leaf() does not cover kernel-only leaf mappings. */
+ if (pgtable_l4_enabled && (p4d_val(p4dp_get(p4dp)) & _PAGE_LEAF)) {
struct page *pud_page;
unsigned long pfn = _p4d_pfn(p4dp_get(p4dp));
pgprot_t prot = __pgprot(p4d_val(p4dp_get(p4dp)) & ~_PAGE_PFN_MASK);
--
2.43.0
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WARNING: multiple messages have this Message-ID (diff)
From: Jackie Liu <liu.yun@linux.dev>
To: akpm@linux-foundation.org
Cc: palmer@dabbelt.com, aou@eecs.berkeley.edu, glider@google.com,
dvyukov@google.com, elver@google.com, pjw@kernel.org,
alex@ghiti.fr, linux-riscv@lists.infradead.org,
linux-mm@kvack.org, kasan-dev@googlegroups.com
Subject: [PATCH 1/2] riscv: Recognize P4D leaves when splitting the linear mapping
Date: Fri, 30 Oct 2026 18:59:32 +0800 [thread overview]
Message-ID: <20261030105933.4180-2-liu.yun@linux.dev> (raw)
In-Reply-To: <20261030105933.4180-1-liu.yun@linux.dev>
From: Jackie Liu <liuyun01@kylinos.cn>
The linear mapping can contain P4D leaves on Sv57, but p4d_leaf() uses
the generic definition which always returns false. Splitting a partial
P4D range therefore treats the mapped physical memory as a PUD table
instead of allocating and populating that table.
Check the hardware leaf bits in the linear-map splitter. Only do so
when the PUD level is present: on Sv39 the folded P4D entry may contain
a PUD leaf, which must be handled by the PUD splitter.
Keep this check local to kernel mappings. Defining p4d_leaf() globally
would conflict with the GUP assertions that userspace P4D leaves are
unsupported.
Link: https://lore.kernel.org/all/sashiko-outbox-190189@kernel.org/
Fixes: 311cd2f6e253 ("riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge linear mappings")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
arch/riscv/mm/pageattr.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 5b3cf326455db..32834a09a8097 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -197,7 +197,8 @@ static int __split_linear_mapping_p4d(pgd_t *pgdp,
vaddr <= (vaddr & P4D_MASK) && end >= next)
continue;
- if (p4d_leaf(p4dp_get(p4dp))) {
+ /* p4d_leaf() does not cover kernel-only leaf mappings. */
+ if (pgtable_l4_enabled && (p4d_val(p4dp_get(p4dp)) & _PAGE_LEAF)) {
struct page *pud_page;
unsigned long pfn = _p4d_pfn(p4dp_get(p4dp));
pgprot_t prot = __pgprot(p4d_val(p4dp_get(p4dp)) & ~_PAGE_PFN_MASK);
--
2.43.0
next prev parent reply other threads:[~2026-10-30 11:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-30 10:59 [PATCH 0/2] riscv: fix KFENCE pool initialization Jackie Liu
2026-10-30 10:59 ` Jackie Liu
2026-10-30 10:59 ` Jackie Liu [this message]
2026-10-30 10:59 ` [PATCH 1/2] riscv: Recognize P4D leaves when splitting the linear mapping Jackie Liu
2026-10-30 10:59 ` [PATCH 2/2] riscv: Prepare late KFENCE pools with PTE mappings Jackie Liu
2026-10-30 10:59 ` Jackie Liu
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