* enabling kvm w/SPLIT_PTLOCK_CPUS > NR_CPUS fails to build in pgtable.c
@ 2014-12-31 5:56 Mike Frysinger
0 siblings, 0 replies; 2+ messages in thread
From: Mike Frysinger @ 2014-12-31 5:56 UTC (permalink / raw)
To: linux-s390
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i've configured my kernel to have:
CONFIG_KVM=3Dy
CONFIG_NR_CPUS=3D2
CONFIG_SPLIT_PTLOCK_CPUS=3D4
and that makes the build very unhappy:
CC arch/s390/mm/pgtable.o
arch/s390/mm/pgtable.c: In function =E2=80=98__gmap_segment_gaddr=E2=80=99:
arch/s390/mm/pgtable.c:327:2: error: implicit declaration of function=20
=E2=80=98pmd_to_page=E2=80=99 [-Werror=3Dimplicit-function-declaration]
page =3D pmd_to_page((pmd_t *) entry);
^
this is because include/linux/mm_types.h has:
#define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
and include/linux/mm.h has:
#if USE_SPLIT_PMD_PTLOCKS
static struct page *pmd_to_page(pmd_t *pmd)
...
i did set NR_CPUS down on purpose (this system only has two cpus), but=20
apparently tweaking SPLIT_PTLOCK_CPUS isn't an option :). in mm/Kconfig:
config SPLIT_PTLOCK_CPUS
int
default "4"
-mike
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: enabling kvm w/SPLIT_PTLOCK_CPUS > NR_CPUS fails to build in pgtable.c
[not found] <20150102103136.GB4059@osiris>
@ 2015-01-05 8:57 ` Martin Schwidefsky
0 siblings, 0 replies; 2+ messages in thread
From: Martin Schwidefsky @ 2015-01-05 8:57 UTC (permalink / raw)
To: linux-s390
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On Fri, 2 Jan 2015 11:31:36 +0100
Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> On Wed, Dec 31, 2014 at 12:56:59AM -0500, Mike Frysinger wrote:
> > i've configured my kernel to have:
> > CONFIG_KVM=y
> > CONFIG_NR_CPUS=2
> > CONFIG_SPLIT_PTLOCK_CPUS=4
> >
> > and that makes the build very unhappy:
> > CC arch/s390/mm/pgtable.o
> > arch/s390/mm/pgtable.c: In function ���__gmap_segment_gaddr���:
> > arch/s390/mm/pgtable.c:327:2: error: implicit declaration of function
> > ���pmd_to_page��� [-Werror=implicit-function-declaration]
> > page = pmd_to_page((pmd_t *) entry);
> > ^
> >
> > this is because include/linux/mm_types.h has:
> > #define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
> > IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
> >
> > and include/linux/mm.h has:
> > #if USE_SPLIT_PMD_PTLOCKS
> > static struct page *pmd_to_page(pmd_t *pmd)
> > ...
> >
> > i did set NR_CPUS down on purpose (this system only has two cpus), but
> > apparently tweaking SPLIT_PTLOCK_CPUS isn't an option :). in mm/Kconfig:
> > config SPLIT_PTLOCK_CPUS
> > int
> > default "4"
> > -mike
>
> Thanks for reporting. The patch below should fix it (adding Martin to To:)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f80d0194c9bc..4ee25aea7861 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1555,14 +1555,14 @@ static inline void pgtable_page_dtor(struct page *page)
> ((unlikely(pmd_none(*(pmd))) && __pte_alloc_kernel(pmd, address))? \
> NULL: pte_offset_kernel(pmd, address))
>
> -#if USE_SPLIT_PMD_PTLOCKS
> -
> -static struct page *pmd_to_page(pmd_t *pmd)
> +static inline struct page *pmd_to_page(pmd_t *pmd)
> {
> unsigned long mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
> return virt_to_page((void *)((unsigned long) pmd & mask));
> }
>
> +#if USE_SPLIT_PMD_PTLOCKS
> +
> static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
> {
> return ptlock_ptr(pmd_to_page(pmd));
That looks good, there is no reason why the pmd_to_page helper should be
conditional on the USE_SPLIT_PMD_PTLOCKS define.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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2014-12-31 5:56 enabling kvm w/SPLIT_PTLOCK_CPUS > NR_CPUS fails to build in pgtable.c Mike Frysinger
[not found] <20150102103136.GB4059@osiris>
2015-01-05 8:57 ` Martin Schwidefsky
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