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Date:   Tue, 21 Apr 2020 07:58:37 +0100
From:   Will Deacon <will@kernel.org>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     Anders Roxell <anders.roxell@linaro.org>, Qian Cai <cai@lca.pw>,
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        Albert Ou <aou@eecs.berkeley.edu>,
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        Peter Xu <peterx@redhat.com>,
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        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v3 0/4] Clean up hugetlb boot command line processing
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On Mon, Apr 20, 2020 at 02:40:05PM -0700, Mike Kravetz wrote:
> On 4/20/20 1:29 PM, Anders Roxell wrote:
> > On Mon, 20 Apr 2020 at 20:23, Mike Kravetz <mike.kravetz@oracle.com> wrote:
> >> On 4/20/20 8:34 AM, Qian Cai wrote:
> >>>
> >>> Reverted this series fixed many undefined behaviors on arm64 with the config,
> >> While rearranging the code (patch 3 in series), I made the incorrect
> >> assumption that CONT_XXX_SIZE == (1UL << CONT_XXX_SHIFT).  However,
> >> this is not the case.  Does the following patch fix these issues?
> >>
> >> From b75cb4a0852e208bee8c4eb347dc076fcaa88859 Mon Sep 17 00:00:00 2001
> >> From: Mike Kravetz <mike.kravetz@oracle.com>
> >> Date: Mon, 20 Apr 2020 10:41:18 -0700
> >> Subject: [PATCH] arm64/hugetlb: fix hugetlb initialization
> >>
> >> When calling hugetlb_add_hstate() to initialize a new hugetlb size,
> >> be sure to use correct huge pages size order.
> >>
> >> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> >> ---
> >>  arch/arm64/mm/hugetlbpage.c | 8 ++++----
> >>  1 file changed, 4 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> >> index 9ca840527296..a02411a1f19a 100644
> >> --- a/arch/arm64/mm/hugetlbpage.c
> >> +++ b/arch/arm64/mm/hugetlbpage.c
> >> @@ -453,11 +453,11 @@ void huge_ptep_clear_flush(struct vm_area_struct *vma,
> >>  static int __init hugetlbpage_init(void)
> >>  {
> >>  #ifdef CONFIG_ARM64_4K_PAGES
> >> -       hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
> >> +       hugetlb_add_hstate(ilog2(PUD_SIZE) - PAGE_SHIFT);
> >>  #endif
> >> -       hugetlb_add_hstate(CONT_PMD_SHIFT - PAGE_SHIFT);
> >> -       hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
> >> -       hugetlb_add_hstate(CONT_PTE_SHIFT - PAGE_SHIFT);
> >> +       hugetlb_add_hstate(ilog2(CONT_PMD_SIZE) - PAGE_SHIFT);
> >> +       hugetlb_add_hstate(ilog2(PMD_SIZE) - PAGE_SHIFT);
> >> +       hugetlb_add_hstate(ilog2(CONT_PTE_SIZE) - PAGE_SHIFT);
> >>
> >>         return 0;
> >>  }
> > 
> > I build this for an arm64 kernel and ran it in qemu and it worked.
> 
> Thanks for testing Anders!
> 
> Will, here is an updated version of the patch based on your suggestion.
> I added the () for emphasis but that may just be noise for some.  Also,
> the naming differences and values for CONT_PTE may make some people
> look twice.  Not sure if being consistent here helps?

Cheers, thanks for this. I think being consistent is worthwhile, as it's
the definitions themselves that are weird and we can conceivably clean
that up as a separate patch.

So,

Acked-by: Will Deacon <will@kernel.org>

Looks like Andrew already picked it up (thanks!)

Thanks,

Will