lkml.org 
[lkml]   [2012]   [Oct]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] s390: Add pmd_mknotpresent()
On Mon, 29 Oct 2012 12:05:19 +0100
Ingo Molnar <mingo@kernel.org> wrote:

>
> * Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
>
> > On Sun, 28 Oct 2012 14:10:14 +0100
> > Ingo Molnar <mingo@kernel.org> 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.
>
> Would be nice if you could send me your suggested
> pmd_mknotpresent().
>
> (Writing it into the email would be enough, I can turn it into a
> patch - but a patch would be welcome as well.)

This would look like the following, the patch should apply to all recent
kernel version.
--
Subject: [PATCH] s390,mm: add pmd_mknotpresent

Fix the following build problem in huge_memory:

mm/huge_memory.c:1543:2: error: implicit declaration of function 'pmd_mknotpresent'

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
arch/s390/include/asm/pgtable.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 335b601..4a84431 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1326,6 +1326,13 @@ 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_INV;
+ pmd_val(pmd) &= ~_SEGMENT_ENTRY_RO;
+ 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.



\
 
 \ /
  Last update: 2012-10-29 13:01    [W:0.058 / U:1.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site