Re: [PATCH v21 10/26] x86/mm: Update pte_modify for _PAGE_COW

[Yu, Yu-cheng]

On 3/5/2021 6:29 AM, Borislav Petkov wrote:
> On Wed, Feb 17, 2021 at 02:27:14PM -0800, Yu-cheng Yu wrote:
> > @@ -787,16 +802,34 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
> >   	 */
> >   	val &= _PAGE_CHG_MASK;
> >   	val |= check_pgprot(newprot) & ~_PAGE_CHG_MASK;
> > +	val = fixup_dirty_pte(val);
>
> Do I see it correctly that you can do here and below:
>
> 	/*
> 	 * Fix up potential shadow stack page flags because the RO, Dirty PTE is
> 	 * special.
> 	 */
> 	if (pte_dirty()) {
> 		pte_mkclean();
> 		pte_mkdirty();
> 	}
>
> ?

Yes, this looks better.  Thanks!

> That fixup thing looks grafted and not like a normal flow to me.