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));
--
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