Re: [PATCH v3 02/11] arm64: hugetlb: Refine tlb maintenance scope

[Catalin Marinas <catalin.marinas@arm.com>]

On Tue, Mar 04, 2025 at 03:04:32PM +0000, Ryan Roberts wrote:
> When operating on contiguous blocks of ptes (or pmds) for some hugetlb
> sizes, we must honour break-before-make requirements and clear down the
> block to invalid state in the pgtable then invalidate the relevant tlb
> entries before making the pgtable entries valid again.
> 
> However, the tlb maintenance is currently always done assuming the worst
> case stride (PAGE_SIZE), last_level (false) and tlb_level
> (TLBI_TTL_UNKNOWN). We can do much better with the hinting; In reality,
> we know the stride from the huge_pte pgsize, we are always operating
> only on the last level, and we always know the tlb_level, again based on
> pgsize. So let's start providing these hints.
> 
> Additionally, avoid tlb maintenace in set_huge_pte_at().
> Break-before-make is only required if we are transitioning the
> contiguous pte block from valid -> valid. So let's elide the
> clear-and-flush ("break") if the pte range was previously invalid.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>