lkml.org 
[lkml]   [2022]   [Jul]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] MIPS: fix pmd_mkinvalid
From
Date
On 2022/7/7 下午5:22, Thomas Bogendoerfer wrote:
> On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote:
>> When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
>> return true.
>> So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
>> present but invalidated by pmd_mkinvalid.
>
> What problem are you trying to fix ? What are the symptoms ?
>
>> Reported-by: kernel test robot <lkp@intel.com>
>
> the test robot showed problems with your last version of the patch,
> which hasn't been integrated into at least the MIPS tree, so no
> need to that.
>
> Thomas.
>

Hi Thomas,
The idea come from the commit:
b65399f6111b(arm64/mm: Change THP helpers to comply with generic MM
semantics).
There is an problem now:
CPU 0 CPU 1
pmdp_invalidate do_page_fault
... __handle_mm_fault
is_swap_pmd == true
trigger VM_BUG_ON() ?
set_pmd_at
the reason is that pmd_present return true,after this commit
pmd_present will return false,and the VM_BUG_ON will not be triggered.
Like arm64 does,we can introduce a new bit to fix this.

Thanks.

\
 
 \ /
  Last update: 2022-07-07 13:14    [W:0.235 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site