s390/kvm: support collaborative memory management
This patch enables Collaborative Memory Management (CMM) for kvm
on s390. CMM allows the guest to inform the host about page usage
(see arch/s390/mm/cmm.c). The host uses this information to avoid
swapping in unused pages in the page fault handler. Further, a CPU
provided list of unused invalid pages is processed to reclaim swap
space of not yet accessed unused pages.
[ Martin Schwidefsky: patch reordering and cleanup ]
Signed-off-by: Konstantin Weitz <konstantin.weitz@gmail.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 3584ed9..9e2b470 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -17,6 +17,7 @@
#include <linux/quicklist.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
+#include <linux/swapops.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -594,6 +595,82 @@
}
EXPORT_SYMBOL_GPL(gmap_fault);
+static void gmap_zap_swap_entry(swp_entry_t entry, struct mm_struct *mm)
+{
+ if (!non_swap_entry(entry))
+ dec_mm_counter(mm, MM_SWAPENTS);
+ else if (is_migration_entry(entry)) {
+ struct page *page = migration_entry_to_page(entry);
+
+ if (PageAnon(page))
+ dec_mm_counter(mm, MM_ANONPAGES);
+ else
+ dec_mm_counter(mm, MM_FILEPAGES);
+ }
+ free_swap_and_cache(entry);
+}
+
+/**
+ * The mm->mmap_sem lock must be held
+ */
+static void gmap_zap_unused(struct mm_struct *mm, unsigned long address)
+{
+ unsigned long ptev, pgstev;
+ spinlock_t *ptl;
+ pgste_t pgste;
+ pte_t *ptep, pte;
+
+ ptep = get_locked_pte(mm, address, &ptl);
+ if (unlikely(!ptep))
+ return;
+ pte = *ptep;
+ if (!pte_swap(pte))
+ goto out_pte;
+ /* Zap unused and logically-zero pages */
+ pgste = pgste_get_lock(ptep);
+ pgstev = pgste_val(pgste);
+ ptev = pte_val(pte);
+ if (((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED) ||
+ ((pgstev & _PGSTE_GPS_ZERO) && (ptev & _PAGE_INVALID))) {
+ gmap_zap_swap_entry(pte_to_swp_entry(pte), mm);
+ pte_clear(mm, address, ptep);
+ }
+ pgste_set_unlock(ptep, pgste);
+out_pte:
+ pte_unmap_unlock(*ptep, ptl);
+}
+
+/*
+ * this function is assumed to be called with mmap_sem held
+ */
+void __gmap_zap(unsigned long address, struct gmap *gmap)
+{
+ unsigned long *table, *segment_ptr;
+ unsigned long segment, pgstev, ptev;
+ struct gmap_pgtable *mp;
+ struct page *page;
+
+ segment_ptr = gmap_table_walk(address, gmap);
+ if (IS_ERR(segment_ptr))
+ return;
+ segment = *segment_ptr;
+ if (segment & _SEGMENT_ENTRY_INVALID)
+ return;
+ page = pfn_to_page(segment >> PAGE_SHIFT);
+ mp = (struct gmap_pgtable *) page->index;
+ address = mp->vmaddr | (address & ~PMD_MASK);
+ /* Page table is present */
+ table = (unsigned long *)(segment & _SEGMENT_ENTRY_ORIGIN);
+ table = table + ((address >> 12) & 0xff);
+ pgstev = table[PTRS_PER_PTE];
+ ptev = table[0];
+ /* quick check, checked again with locks held */
+ if (((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED) ||
+ ((pgstev & _PGSTE_GPS_ZERO) && (ptev & _PAGE_INVALID)))
+ gmap_zap_unused(gmap->mm, address);
+}
+EXPORT_SYMBOL_GPL(__gmap_zap);
+
void gmap_discard(unsigned long from, unsigned long to, struct gmap *gmap)
{