Re: [PATCH v13 3/3] arm64: Implement page table free interfaces

Catalin Marinas
2018-09-21T09:56:14Z

On Thu, Sep 20, 2018 at 06:25:29PM +0100, Catalin Marinas wrote:
> On Wed, Jun 06, 2018 at 12:31:21PM +0530, Chintan Pandya wrote:
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 8ae5d7a..65f8627 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -45,6 +45,7 @@
> > #include <asm/memblock.h>
> > #include <asm/mmu_context.h>
> > #include <asm/ptdump.h>
> > +#include <asm/tlbflush.h>
> >
> > #define NO_BLOCK_MAPPINGS BIT(0)
> > #define NO_CONT_MAPPINGS BIT(1)
> > @@ -977,12 +978,51 @@ int pmd_clear_huge(pmd_t *pmdp)
> > return 1;
> > }
> >
> > -int pud_free_pmd_page(pud_t *pud, unsigned long addr)
> > +int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
> > {
> > - return pud_none(*pud);
> > + pte_t *table;
> > + pmd_t pmd;
> > +
> > + pmd = READ_ONCE(*pmdp);
> > +
> > + /* No-op for empty entry and WARN_ON for valid entry */
> > + if (!pmd_present(pmd) || !pmd_table(pmd)) {
> > + VM_WARN_ON(!pmd_table(pmd));
> > + return 1;
> > + }
>
> What's this VM_WARN_ON supposed to do here? If the pmd is 0, we trigger
> it all the time. Did you actually mean something like:
>
> VM_WARN_ON(!pmd_none(pmd));
>
> or pmd_present(pmd)?
>
> Since the comment mentions empty entry, I'd rather make it explicit:
>
> if (pmd_none(pmd) || !pmd_table(pmd))
> VM_WARN_ON(!pmd_none(pmd));
> return 1;
> }

Ignore this, fixed in -rc4 (fac880c7d074 "arm64: fix erroneous warnings
in page freeing functions").

--
Catalin