* [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v3
@ 2017-06-24 18:05 jglisse
2017-06-26 9:43 ` Ingo Molnar
0 siblings, 1 reply; 3+ messages in thread
From: jglisse @ 2017-06-24 18:05 UTC (permalink / raw)
To: linux-mm
Cc: linux-kernel, Jérôme Glisse, Andy Lutomirski,
Ingo Molnar, Logan Gunthorpe, Andrew Morton
From: JA(C)rA'me Glisse <jglisse@redhat.com>
With commit af2cf278ef4f we no longer free pud so that we do not
have synchronize all pgd on hotremove/vfree. But the new 5 level
page table patchset reverted that for 4 level page table.
This patch restore af2cf278ef4f and disable free_pud() if we are
in the 4 level page table case thus avoiding BUG_ON() after hot-
remove.
af2cf278ef4f x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()
Changed since v2:
- nove to if the callsite instead of having special version of
free_pud for 4 level page table
Changed since v1:
- make free_pud() conditional on the number of page table
level
- improved commit message
Signed-off-by: JA(C)rA'me Glisse <jglisse@redhat.com>
Reviwed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
arch/x86/mm/init_64.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 95651dc58e09..dc4c99f9ca58 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -990,7 +990,13 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end,
pud_base = pud_offset(p4d, 0);
remove_pud_table(pud_base, addr, next, direct);
- free_pud_table(pud_base, p4d);
+ /*
+ * For 4 levels page table we do not want to free puds but for
+ * 5 levels we should free them. This code also need to change
+ * to adapt for boot time switching between 4 and 5 level.
+ */
+ if (CONFIG_PGTABLE_LEVELS == 5)
+ free_pud_table(pud_base, p4d);
}
if (direct)
--
2.13.0
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v3
2017-06-24 18:05 [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v3 jglisse
@ 2017-06-26 9:43 ` Ingo Molnar
2017-06-26 14:49 ` Jerome Glisse
0 siblings, 1 reply; 3+ messages in thread
From: Ingo Molnar @ 2017-06-26 9:43 UTC (permalink / raw)
To: jglisse
Cc: linux-mm, linux-kernel, Andy Lutomirski, Logan Gunthorpe, Andrew Morton
* jglisse@redhat.com <jglisse@redhat.com> wrote:
> From: Jerome Glisse <jglisse@redhat.com>
>
> With commit af2cf278ef4f we no longer free pud so that we do not
> have synchronize all pgd on hotremove/vfree. But the new 5 level
> page table patchset reverted that for 4 level page table.
>
> This patch restore af2cf278ef4f and disable free_pud() if we are
> in the 4 level page table case thus avoiding BUG_ON() after hot-
> remove.
>
> af2cf278ef4f x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()
Am I correct that the _real_ buggy commit that introduced the breakage in v4.12
is:
f2a6a7050109: ("x86: Convert the rest of the code to support p4d_t")
... right?
Thanks,
Ingo
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v3
2017-06-26 9:43 ` Ingo Molnar
@ 2017-06-26 14:49 ` Jerome Glisse
0 siblings, 0 replies; 3+ messages in thread
From: Jerome Glisse @ 2017-06-26 14:49 UTC (permalink / raw)
To: Ingo Molnar
Cc: linux-mm, linux-kernel, Andy Lutomirski, Logan Gunthorpe, Andrew Morton
On Mon, Jun 26, 2017 at 11:43:04AM +0200, Ingo Molnar wrote:
>
> * jglisse@redhat.com <jglisse@redhat.com> wrote:
>
> > From: Jerome Glisse <jglisse@redhat.com>
> >
> > With commit af2cf278ef4f we no longer free pud so that we do not
> > have synchronize all pgd on hotremove/vfree. But the new 5 level
> > page table patchset reverted that for 4 level page table.
> >
> > This patch restore af2cf278ef4f and disable free_pud() if we are
> > in the 4 level page table case thus avoiding BUG_ON() after hot-
> > remove.
> >
> > af2cf278ef4f x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()
>
> Am I correct that the _real_ buggy commit that introduced the breakage in v4.12
> is:
>
> f2a6a7050109: ("x86: Convert the rest of the code to support p4d_t")
>
> ... right?
Correct.
Jerome
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2017-06-26 9:43 ` Ingo Molnar
2017-06-26 14:49 ` Jerome Glisse
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