Re: [linux-next:pending-fixes] [mm/hugetlb] d3fe1a0a02: WARNING:at_include/linux/hugetlb.h:#huge_pte_lockptr

[David Hildenbrand <david@redhat.com>]

On 31.07.24 10:16, David Hildenbrand wrote:
> On 31.07.24 09:20, kernel test robot wrote:
>>
>>
>> Hello,
>>
>> kernel test robot noticed "WARNING:at_include/linux/hugetlb.h:#huge_pte_lockptr" on:
>>
>> commit: d3fe1a0a0272723474056e3000717d69923ad901 ("mm/hugetlb: fix hugetlb vs. core-mm PT locking")
>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git pending-fixes
>>
>> [test failed on linux-next/master cd19ac2f903276b820f5d0d89de0c896c27036ed]
>>
>> in testcase: trinity
>> version: trinity-i386-abe9de86-1_20230429
>> with following parameters:
>>
>> 	runtime: 300s
>> 	group: group-00
>> 	nr_groups: 5
>>
>>
>>
>> compiler: gcc-11
>> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>>
>> (please refer to attached dmesg/kmsg for entire log/backtrace)
>>
>>
>> +------------------------------------------------------+------------+------------+
>> |                                                      | e98970a1d2 | d3fe1a0a02 |
>> +------------------------------------------------------+------------+------------+
>> | WARNING:at_include/linux/hugetlb.h:#huge_pte_lockptr | 0          | 12         |
>> | EIP:huge_pte_lockptr                                 | 0          | 12         |
>> +------------------------------------------------------+------------+------------+
>>
>>
>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>> the same patch/commit), kindly add following tags
>> | Reported-by: kernel test robot <oliver.sang@intel.com>
>> | Closes: https://lore.kernel.org/oe-lkp/202407311421.95f5c759-lkp@intel.com
>>
>>
>> [   39.570466][ T3479] ------------[ cut here ]------------
>> [ 39.570921][ T3479] WARNING: CPU: 0 PID: 3479 at include/linux/hugetlb.h:948 huge_pte_lockptr (include/linux/hugetlb.h:948 (discriminator 1))
> 
> Helpful! Likely triggers because in that kernel cfg P4D_SIZE is 0.

Hm, with !CONFIG_X86_5LEVEL we should have

#define PGDIR_SHIFT 39
#define P4D_SHIFT PGDIR_SHIFT
#define P4D_SIZE (1UL << P4D_SHIFT)

... getting a hugepage size >= P4D_SIZE seems pretty much impossible.

Anyhow, taking the easy route to be done with his hugetlb crap and live 
a happy live, I'll drop the warning and just handle it explicitly.

-- 
Cheers,

David / dhildenb