Re: [PATCH] arm64: mm: Fix the break-before-make flush range for erratum 2645198

[Will Deacon]

On Wed, 23 Sep 2026 16:36:32 +0200, Andrea Parri wrote:
> modify_prot_start_ptes() performs the break-before-make TLB invalidation
> required by erratum 2645198 with __flush_tlb_range(), whose third
> argument is the end address of the range.  It passes nr * PAGE_SIZE
> instead of addr + nr * PAGE_SIZE, so __do_flush_tlb_range() computes the
> page count as (nr * PAGE_SIZE - addr) >> PAGE_SHIFT.
> 
> For addr > nr * PAGE_SIZE that subtraction underflows, the page count
> exceeds the batching limit and the flush degenerates to flush_tlb_mm(),
> so a single-page mprotect broadcasts an ASID-wide invalidation and a
> full-range mmu notifier call.
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] arm64: mm: Fix the break-before-make flush range for erratum 2645198
      https://git.kernel.org/arm64/c/1fef81669147

Cheers,
-- 
Will

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