+ riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap.patch added to mm-nonmm-unstable branch

+ riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: riscv: mm: avoid spurious fault after hotplugging vmemmap
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Vivian Wang <wangruikang@iscas.ac.cn>
Subject: riscv: mm: avoid spurious fault after hotplugging vmemmap
Date: Tue, 30 Jun 2026 15:51:59 +0800

section_activate() does not flush TLB after populating new vmemmap pages. 
On most architectures, this is okay.  However it is a problem on RISC-V
since there the TLB caching non-present entries is permitted, which causes
spurious faults on some hardwares.

This seems to be most easily reproduced with DEBUG_VM=y and
PAGE_POISONING=y, which causes these newly mapped struct pages to be
poisoned i.e.  written to immediately after mapping.

Add a hook vmemmap_populate_finalize() in __populate_section_memmap()
after population, to allow architectures to handle such situations as
needed.  Then implement it on RISC-V to arrange for the existing exception
handler code to deal with these faults if they happen.

Link: https://lore.kernel.org/20260630-mark-after-vmemmap-populate-v4-1-febbc15da028@iscas.ac.cn
Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/riscv/include/asm/pgtable.h |    4 ++++
 arch/riscv/mm/init.c             |    6 ++++++
 mm/sparse-vmemmap.c              |    8 ++++++++
 3 files changed, 18 insertions(+)

--- a/arch/riscv/include/asm/pgtable.h~riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap
+++ a/arch/riscv/include/asm/pgtable.h
@@ -1260,6 +1260,10 @@ static inline pte_t pte_swp_clear_exclus
 #define TASK_SIZE	FIXADDR_START
 #endif
 
+/* Needed on SPARSEMEM_VMEMMAP */
+#define vmemmap_populate_finalize vmemmap_populate_finalize
+void __meminit vmemmap_populate_finalize(void);
+
 #else /* CONFIG_MMU */
 
 #define PAGE_SHARED		__pgprot(0)
--- a/arch/riscv/mm/init.c~riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap
+++ a/arch/riscv/mm/init.c
@@ -1372,6 +1372,12 @@ int __meminit vmemmap_populate(unsigned
 	 */
 	return vmemmap_populate_hugepages(start, end, node, altmap);
 }
+
+void __meminit vmemmap_populate_finalize(void)
+{
+	/* Avoid faults on cached non-present TLB entries. */
+	mark_new_valid_map();
+}
 #endif
 
 #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
--- a/mm/sparse-vmemmap.c~riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap
+++ a/mm/sparse-vmemmap.c
@@ -544,6 +544,12 @@ static int __meminit vmemmap_populate_co
 
 #endif
 
+#ifndef vmemmap_populate_finalize
+static void __meminit vmemmap_populate_finalize(void)
+{
+}
+#endif
+
 struct page * __meminit __populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
 		struct dev_pagemap *pgmap)
@@ -564,6 +570,8 @@ struct page * __meminit __populate_secti
 	if (r < 0)
 		return NULL;
 
+	vmemmap_populate_finalize();
+
 	return pfn_to_page(pfn);
 }
 
_

Patches currently in -mm which might be from wangruikang@iscas.ac.cn are

riscv-mm-avoid-spurious-fault-after-hotplugging-vmemmap.patch