Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> wrote:
> Michael Neuling <mi...@neuling.org> writes:
>
> > Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> wrote:
> >
> >> From: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com>
> >>
> >> Book3E uses the hugepd at PMD level and don't encode pte directly
> >> at the pmd level. So it will find the lower bits of pmd set
> >> and the pmd_bad check throws error. Infact the current code
> >> will never take the free_hugepd_range call at all because it will
> >> clear the pmd if it find a hugepd pointer.
> >>
> >
> > Please explain what changes you are making. Currently you are only
> > describing what the issue is.
>
> will do
>
> >
> > Also include which the SHA1 which caused the regression (ie
> > e2b3d202d1dba8f3546ed28224ce485bc50010be "powerpc: Switch 16GB and 16MB
> > explicit hugepages to a different page table format")
>
> will add
>
> >
> > Mikey
> >
> >> Reported-by: Scott Wood <scottw...@freescale.com>
> >> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> >> ---
> >> arch/powerpc/mm/hugetlbpage.c | 29 ++++++++++++++++++-----------
> >> 1 file changed, 18 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> >> index f2f01fd..0d3d3ee 100644
> >> --- a/arch/powerpc/mm/hugetlbpage.c
> >> +++ b/arch/powerpc/mm/hugetlbpage.c
> >> @@ -536,19 +536,26 @@ static void hugetlb_free_pmd_range(struct mmu_gather
> >> *tlb, pud_t *pud,
> >> do {
> >> pmd = pmd_offset(pud, addr);
> >> next = pmd_addr_end(addr, end);
> >> - if (pmd_none_or_clear_bad(pmd))
> >> - continue;
> >> + if (!is_hugepd(pmd)) {
> >> + /*
> >> + * if it is not hugepd pointer, we should already find
> >> + * it cleared.
> >> + */
> >> + if (!pmd_none_or_clear_bad(pmd))
> >> + WARN_ON(1);
> >
> > How often are we going to hit this? Should this be a warn_on once or
> > even a bug_on?
>
> it should never happen. But i was thinking killing the system may a bit
> too much, hence WARN_ON
Maybe WARN_ON_ONCE. If you do hit it once, you are going to hit it a
lot?
Mikey
>
> >
> > Also just make it:
> > WARN_ON(!pmd_none_or_clear_bad(pmd))
> >
>
> will do
>
> -aneesh
>
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