Re: [PATCH v3 06/13] mm/debug_vm_pgtable/THP: Mark the pte entry huge before using set_pmd/pud_at

["Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>]

On 9/1/20 8:51 AM, Anshuman Khandual wrote:
> On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
> > kernel expects entries to be marked huge before we use set_pmd_at()/set_pud_at().
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> > ---
> >   mm/debug_vm_pgtable.c | 21 ++++++++++++---------
> >   1 file changed, 12 insertions(+), 9 deletions(-)
> >
> > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> > index 5c0680836fe9..de83a20c1b30 100644
> > --- a/mm/debug_vm_pgtable.c
> > +++ b/mm/debug_vm_pgtable.c
> > @@ -155,7 +155,7 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
> >   				      unsigned long pfn, unsigned long vaddr,
> >   				      pgprot_t prot)
> >   {
> > -	pmd_t pmd = pfn_pmd(pfn, prot);
> > +	pmd_t pmd;
> >   
> >   	if (!has_transparent_hugepage())
> >   		return;
> > @@ -164,19 +164,19 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
> >   	/* Align the address wrt HPAGE_PMD_SIZE */
> >   	vaddr = (vaddr & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
> >   
> > -	pmd = pfn_pmd(pfn, prot);
> > +	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
> >   	set_pmd_at(mm, vaddr, pmdp, pmd);
> >   	pmdp_set_wrprotect(mm, vaddr, pmdp);
> >   	pmd = READ_ONCE(*pmdp);
> >   	WARN_ON(pmd_write(pmd));
> >   
> > -	pmd = pfn_pmd(pfn, prot);
> > +	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
> >   	set_pmd_at(mm, vaddr, pmdp, pmd);
> >   	pmdp_huge_get_and_clear(mm, vaddr, pmdp);
> >   	pmd = READ_ONCE(*pmdp);
> >   	WARN_ON(!pmd_none(pmd));
> >   
> > -	pmd = pfn_pmd(pfn, prot);
> > +	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
> >   	pmd = pmd_wrprotect(pmd);
> >   	pmd = pmd_mkclean(pmd);
> >   	set_pmd_at(mm, vaddr, pmdp, pmd);
> > @@ -237,7 +237,7 @@ static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot)
> >   
> >   static void __init pmd_savedwrite_tests(unsigned long pfn, pgprot_t prot)
> >   {
> > -	pmd_t pmd = pfn_pmd(pfn, prot);
> > +	pmd_t pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
>
> There is no set_pmd_at() in this particular test, why change ?


because if you are building a hugepage you should use pmd_mkhuge(). That 
is what is setting _PAGE_PTE with this series. We don't make pfn_pmd set 
_PAGE_PTE


-aneesh