s390/hugetlb: add hugepages_supported define

On s390 we only can enable hugepages if the underlying hardware/hypervisor
also does support this. Common code now would assume this to be
signaled by setting HPAGE_SHIFT to 0. But on s390, where we only
support one hugepage size, there is a link between HPAGE_SHIFT and
pageblock_order.

So instead of setting HPAGE_SHIFT to 0, we will implement the check for
the hardware capability.

Signed-off-by: Dominik Dingel <[e-mail]>
Acked-by: Martin Schwidefsky <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Christian Borntraeger <[e-mail]>
Cc: Michael Holzheu <[e-mail]>
Cc: Gerald Schaefer <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/s390/include/asm/hugetlb.h

···
 
 #define is_hugepage_only_range(mm, addr, len)	0
 #define hugetlb_free_pgd_range			free_pgd_range
+#define hugepages_supported()			(MACHINE_HAS_HPAGE)
 
 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 		     pte_t *ptep, pte_t pte);