# Re: \[PATCH v21 08/26\] x86/mm: Introduce \_PAGE\_COW

- From: Yu, Yu-cheng \<hidden\>
- Date: 2021-03-03 11:02:24 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/03/6286160
- Thread: https://ratatoskr.run/linux-doc/2021/02/6272416/t.md

```text
On 3/1/2021 7:52 AM, Borislav Petkov wrote:
> On Wed, Feb 17, 2021 at 02:27:12PM -0800, Yu-cheng Yu wrote:

[...]

>>   static inline pmd_t pmd_mkdirty(pmd_t pmd)
>>   {
>> -	return pmd_set_flags(pmd, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
>> +	pmdval_t dirty = _PAGE_DIRTY;
>> +
>> +	/* Avoid creating (HW)Dirty=1, Write=0 PMDs */
>> +	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pmd_flags(pmd) & _PAGE_RW))
>
> 						      !(pmd_write(pmd))
>

There is a problem of doing that: pmd_write() is defined after this function.  Maybe we can declare it first, or leave this as-is?

--
Yu-cheng
```