Re: [PATCH] x86/mm: Make pud_present() check _PAGE_PROTNONE and _PAGE_PSE as well

[Kirill A. Shutemov]

On Fri, Mar 20, 2020 at 08:53:16AM +0530, Anshuman Khandual wrote:
> 
> 
> On 03/18/2020 10:31 AM, Anshuman Khandual wrote:
> > pud_present() should also check _PAGE_PROTNONE and _PAGE_PSE bits like in
> > case pmd_present(). This makes a PUD entry test positive for pud_present()
> > after getting invalidated with pud_mknotpresent(), hence standardizing the
> > semantics with PMD helpers.
> > 
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: linux-mm@xxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > ---
> > Even though pud_mknotpresent() is not used any where currently, there is
> > a discrepancy between PMD and PUD.
> > 
> > WARN_ON(!pud_present(pud_mknotpresent(pud_mkhuge(pud)))) -> Fail
> > WARN_ON(!pmd_present(pmd_mknotpresent(pmd_mkhuge(pmd)))) -> Pass
> > 
> > Though pud_mknotpresent() currently clears _PAGE_PROTNONE, pud_present()
> > does not check it. This change fixes both inconsistencies.
> > 
> > This has been build and boot tested on x86.
> 
> Adding Kirill and Dan.
> 
> +Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
> +Cc: Dan Williams <dan.j.williams@xxxxxxxxx>

Or we can just drop the pud_mknotpresent(). There's no users AFAICS and
only x86 provides it.

-- 
 Kirill A. Shutemov