On Sun, 28 Oct 2012 14:10:14 +0100 Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > There's a related problem on s390: other THP implementations > have pmd_mknotpresent() while s390 not, resulting in: > > mm/huge_memory.c:1543:2: error: implicit declaration of function 'pmd_mknotpresent' > > The (untested!) patch below adds the s390 version of this > method. > > Gerald, Martin, did I get the S390 details right? This won't work I'm afraid. S390 uses invalid bits which need to be set to make an entry not present. Just setting the _SEGMENT_ENTRY_INV bit is not good enough either, there is _HPAGE_TYPE_NONE to consider. The patch to fix this for pmd_none & pmd_present just got added to the s390 tree on kernel.org: https://git.kernel.org/?p=linux/kernel/git/s390/linux.git;a=shortlog;h=refs/heads/fixes Now, if pmd_mknotpresent is supposed to make the entry invalid so that pmd_present will return false the function needs to do two things, 1) set the _SEGMENT_ENTRY_INV bit, and 2) clear the _SEGMENT_ENTRY_RO bit. > diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h > index 098fc5a..b820ff1 100644 > --- a/arch/s390/include/asm/pgtable.h > +++ b/arch/s390/include/asm/pgtable.h > @@ -1310,6 +1310,12 @@ static inline pmd_t pmd_mkyoung(pmd_t pmd) > return pmd; > } > > +static inline pmd_t pmd_mknotpresent(pmd_t pmd) > +{ > + pmd_val(pmd) &= ~_SEGMENT_ENTRY_ORIGIN; > + return pmd; > +} > + > #define __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG > static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, > unsigned long address, pmd_t *pmdp) > -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
