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

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Message-ID: <ZMe0lIQZI2oHDe2o@arm.com>
Date:   Mon, 31 Jul 2023 14:18:12 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Kefeng Wang <wangkefeng.wang@...wei.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 Mon, Jul 31, 2023 at 07:27:14PM +0800, Kefeng Wang wrote:
> 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?

Right. Only the pmd/pud cases.

-- 
Catalin