Re: [RFC PATCH 1/1] arm64: mm: remove unnecessary multiple tlb flush of contiguous hugetlb

[Carlo Bai]

On 2023/2/8 2:21, Catalin Marinas wrote:
> On Tue, Feb 07, 2023 at 07:09:41PM +0800, Kaihao Bai wrote:
> > In arm64, contiguous flag refers to the same TLB entry that shared by a
> > contiguous address range. If flush one entry of the address range, it
> > would cover the whole contiguous address range. Thus there's no need to
> > flush all contiguous range that CONT_PMD/PTE points to.
>
> This doesn't work. The contiguous bit is a hint, so the CPU may not
> coalesce multiple PTEs into a single TLB entry.
> Sorry I misunderstood the underlying approach of contiguous bit. I 
re-check and find that "TLB maintenance must be performed based on the 
size of the underlying translation table entries, to avoid TLB
coherency issues.". Thanks for your clarification!