Re: [PATCH v3 0/4] Clean up hugetlb boot command line processing

[Mike Kravetz]

On 4/20/20 1:29 PM, Anders Roxell wrote:
> On Mon, 20 Apr 2020 at 20:23, Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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@xxxxxxxxxx>
>> 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@xxxxxxxxxx>
>> ---
>>  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?

I have only built this.  No testing.