linux-kernel - Re: [PATCH RFC 00/12] mm/gup: Unify hugetlb, part 2

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Message-ID: <20231122145146.GN6083@nvidia.com>
Date:   Wed, 22 Nov 2023 10:51:46 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Mike Kravetz <mike.kravetz@...cle.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Rapoport <rppt@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        James Houghton <jthoughton@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC 00/12] mm/gup: Unify hugetlb, part 2

On Wed, Nov 15, 2023 at 08:28:56PM -0500, Peter Xu wrote:
> This patchset is in RFC stage. It's mostly because it is only yet tested on
> x86_64 in a VM.  Not even compile tested on PPC or any other archs, it
> means at least the hugepd patch (patch 11) is mostly untested, or even not
> compile tested.  Before doing that, I'd like to collect any information
> from high level.
> 
> If anyone would like to provide any testing either over hugepd or CONT_PMD
> / CONT_PTE on ARM (before I reach there..), or RISCV over 64K Svnapot,
> that'll be very much appreciated.  I'm copying PPC, ARM, RISCV list for
> that.  It can be as simple as "./run_vmtests.sh -t gup_test -a" for now,
> making sure hugetlb pages can be allocated along the way; the non-hugetlb
> gup tests will guaranteed to be covered more or less, I suppose.
> 
> In summary, this is a continuous work for previous series:
> 
> https://lore.kernel.org/all/20230628215310.73782-1-peterx@redhat.com
> 
> And this more or less is my current take to move one more small step
> towards merging hugetlb code into generic mm code, as much as we can.
> 
> That part-1 series dropped follow_hugetlb_page().  The plan of this one is
> to further drops hugetlb_follow_page_mask().  The hugetlb GUP will use the
> same code path for generic mm after whole set applied.
> 
> It means the generic code will need to at least understand hugepd, and
> that's already done like so in fast-gup.  Fortunately it seems that's the
> only major thing I need to teach GUP to share the common path for now
> besides normal huge PxD entries.  Non-gup can be more challenging, but
> that's a question for later.

This is great, I looked through quickly and didn't have any profound remarks

Thanks,
Jason