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

[Anshuman Khandual]

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>