linux-kernel - Re: [PATCH 4/4] arm64: tlb: set huge page size to stride for hugepage

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Message-ID: <70e81ce8-a27a-325f-68d1-836532ed2ba0@huawei.com>
Date:   Mon, 31 Jul 2023 19:27:14 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Catalin Marinas <catalin.marinas@....com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Mina Almasry <almasrymina@...gle.com>, <kirill@...temov.name>,
        <joel@...lfernandes.org>, <william.kucharski@...cle.com>,
        <kaleshsingh@...gle.com>, <linux-mm@...ck.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] arm64: tlb: set huge page size to stride for hugepage



On 2023/7/31 19:11, Catalin Marinas wrote:
> On Mon, Jul 31, 2023 at 03:48:29PM +0800, Kefeng Wang wrote:
>> +/*
>> + * We cannot use leaf-only invalidation here, since we may be invalidating
>> + * table entries as part of collapsing hugepages or moving page tables.
>> + * Set the tlb_level to 0 because we can not get enough information here.
>> + */
>> +#define flush_tlb_range(vma, start, end)				\
>> +	__flush_tlb_range(vma, start, end,				\
>> +				((vma)->vm_flags & VM_HUGETLB)		\
>> +				? huge_page_size(hstate_vma(vma))	\
>> +				: PAGE_SIZE, false, 0)
> 
> This won't work if we use the contiguous PTE to get 64K hugetlb pages on
> a 4K base page configuration. The 16 base pages in the range would have
> to be invalidated individually (the contig PTE bit is just a hint, the
> hardware may or may not take it into account).

Got it, the contig huge page is depended on hardware implementation,
but for normal hugepage(2M/1G), we could use this, right?
>