* [PATCH 6.1 0680/1067] arm64/mm: Optimize TLB flush in unmap_hotplug_[pmd|pud]_range()
[not found] <20260721152424.521567757@linuxfoundation.org>
@ 2026-07-21 15:21 ` Greg Kroah-Hartman
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From: Greg Kroah-Hartman @ 2026-07-21 15:21 UTC (permalink / raw)
To: stable
Cc: Greg Kroah-Hartman, patches, Catalin Marinas, Will Deacon,
Ryan Roberts, David Hildenbrand, linux-arm-kernel, linux-kernel,
Ben Hutchings, Anshuman Khandual, Sasha Levin
6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Anshuman Khandual <anshuman.khandual@arm.com>
[ Upstream commit ff4c5a0de1f2ef7737a8688a86e19301e567020d ]
Commit 48478b9f7913 ("arm64/mm: Enable batched TLB flush in
unmap_hotplug_range") inadvertently introduced redundant TLB
invalidation when clearing a block entry, resulting in unnecessary
broadcast invalidation on CPUs without support for range-based
invalidation.
Re-introduce the old behaviour, along with some expanded comments to
help people working in this area next time around.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Closes: https://lore.kernel.org/all/b0d5836032ce3135bfc473f6bff791306d086925.camel@decadent.org.uk/
Fixes: 48478b9f7913 ("arm64/mm: Enable batched TLB flush in unmap_hotplug_range()")
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[will: Reword comments and commit message]
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/mm/mmu.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 3d7f9732201667..72fb70f2bfb203 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -956,7 +956,13 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
if (free_mapped) {
/* CONT blocks are not supported in the vmemmap */
WARN_ON(pmd_cont(pmd));
- flush_tlb_kernel_range(addr, addr + PMD_SIZE);
+ /*
+ * Invalidating a block entry requires just
+ * a single overlapping TLB invalidation,
+ * so limit the range of the flush to a single
+ * page.
+ */
+ flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
free_hotplug_page_range(pmd_page(pmd),
PMD_SIZE, altmap);
}
@@ -986,7 +992,8 @@ static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
if (pud_sect(pud)) {
pud_clear(pudp);
if (free_mapped) {
- flush_tlb_kernel_range(addr, addr + PUD_SIZE);
+ /* See comment in unmap_hotplug_pmd_range(). */
+ flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
free_hotplug_page_range(pud_page(pud),
PUD_SIZE, altmap);
}
--
2.53.0
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