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arm64/mm: Optimize TLB flush in unmap_hotplug_[pmd|pud]_range()

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Commit 48478b9f79 ("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: 48478b9f79 ("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>
This commit is contained in:
Anshuman Khandual 2026-06-26 02:28:45 +01:00 committed by Will Deacon
parent 534eb6940a
commit ff4c5a0de1
1 changed files with 9 additions and 2 deletions
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11
arch/arm64/mm/mmu.c
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@ -1515,7 +1515,13 @@ 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);
}
@ -1545,7 +1551,8 @@ static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
if (pud_leaf(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);
}