s390/mm: tag normal pages vs pages used in page tables
The ESSA instruction has a new option that allows to tag pages that
are not used as a page table. Without the tag the hypervisor has to
assume that any guest page could be used in a page table inside the
guest. This forces the hypervisor to flush all guest TLB entries
whenever a host page table entry is invalidated. With the tag
the host can skip the TLB flush if the page is tagged as normal page.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
index 18918e3..a4de34c 100644
--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -57,6 +57,7 @@ unsigned long *crst_table_alloc(struct mm_struct *mm)
if (!page)
return NULL;
+ arch_set_page_dat(page, 2);
return (unsigned long *) page_to_phys(page);
}
@@ -214,6 +215,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
__free_page(page);
return NULL;
}
+ arch_set_page_dat(page, 0);
/* Initialize page table */
table = (unsigned long *) page_to_phys(page);
if (mm_alloc_pgste(mm)) {