[S390] guest page hinting light

Use the existing arch_alloc_page/arch_free_page callbacks to do
the guest page state transitions between stable and unused.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

6 files changed, 107 insertions, 0 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 29a7940f284f..1d035082e78e 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -430,6 +430,13 @@ config CMM_IUCV
           Select this option to enable the special message interface to
           the cooperative memory management.
 
+config PAGE_STATES
+        bool "Unused page notification"
+        help
+          This enables the notification of unused pages to the
+          hypervisor. The ESSA instruction is used to do the states
+          changes between a page that has content and the unused state.
+
 config VIRT_TIMER
         bool "Virtual CPU timer support"
         help
diff --git a/arch/s390/mm/Makefile b/arch/s390/mm/Makefile
index fb988a48a754..2a7458134544 100644
--- a/arch/s390/mm/Makefile
+++ b/arch/s390/mm/Makefile
@@ -5,3 +5,4 @@
 obj-y    := init.o fault.o extmem.o mmap.o vmem.o pgtable.o
 obj-$(CONFIG_CMM) += cmm.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
+obj-$(CONFIG_PAGE_STATES) += page-states.o
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index fa31de6ae97a..29f3a63806b9 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -126,6 +126,9 @@ void __init mem_init(void)
         /* clear the zero-page */
         memset(empty_zero_page, 0, PAGE_SIZE);
 
+        /* Setup guest page hinting */
+        cmma_init();
+
         /* this will put all low memory onto the freelists */
         totalram_pages += free_all_bootmem();
 
diff --git a/arch/s390/mm/page-states.c b/arch/s390/mm/page-states.c
new file mode 100644
index 000000000000..fc0ad73ffd90
--- /dev/null
+++ b/arch/s390/mm/page-states.c
@@ -0,0 +1,79 @@
+/*
+ * arch/s390/mm/page-states.c
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * Guest page hinting for unused pages.
+ *
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+
+#define ESSA_SET_STABLE         1
+#define ESSA_SET_UNUSED         2
+
+static int cmma_flag;
+
+static int __init cmma(char *str)
+{
+        char *parm;
+        parm = strstrip(str);
+        if (strcmp(parm, "yes") == 0 || strcmp(parm, "on") == 0) {
+                cmma_flag = 1;
+                return 1;
+        }
+        cmma_flag = 0;
+        if (strcmp(parm, "no") == 0 || strcmp(parm, "off") == 0)
+                return 1;
+        return 0;
+}
+
+__setup("cmma=", cmma);
+
+void __init cmma_init(void)
+{
+        register unsigned long tmp asm("0") = 0;
+        register int rc asm("1") = -EOPNOTSUPP;
+
+        if (!cmma_flag)
+                return;
+        asm volatile(
+                "       .insn rrf,0xb9ab0000,%1,%1,0,0\n"
+                "0:     la      %0,0\n"
+                "1:\n"
+                EX_TABLE(0b,1b)
+                : "+&d" (rc), "+&d" (tmp));
+        if (rc)
+                cmma_flag = 0;
+}
+
+void arch_free_page(struct page *page, int order)
+{
+        int i, rc;
+
+        if (!cmma_flag)
+                return;
+        for (i = 0; i < (1 << order); i++)
+                asm volatile(".insn rrf,0xb9ab0000,%0,%1,%2,0"
+                             : "=&d" (rc)
+                             : "a" ((page_to_pfn(page) + i) << PAGE_SHIFT),
+                               "i" (ESSA_SET_UNUSED));
+}
+
+void arch_alloc_page(struct page *page, int order)
+{
+        int i, rc;
+
+        if (!cmma_flag)
+                return;
+        for (i = 0; i < (1 << order); i++)
+                asm volatile(".insn rrf,0xb9ab0000,%0,%1,%2,0"
+                             : "=&d" (rc)
+                             : "a" ((page_to_pfn(page) + i) << PAGE_SHIFT),
+                               "i" (ESSA_SET_STABLE));
+}
diff --git a/include/asm-s390/page.h b/include/asm-s390/page.h
index f0f4579eac13..12fd9c4f0f15 100644
--- a/include/asm-s390/page.h
+++ b/include/asm-s390/page.h
@@ -125,6 +125,17 @@ page_get_storage_key(unsigned long addr)
         return skey;
 }
 
+#ifdef CONFIG_PAGE_STATES
+
+struct page;
+void arch_free_page(struct page *page, int order);
+void arch_alloc_page(struct page *page, int order);
+
+#define HAVE_ARCH_FREE_PAGE
+#define HAVE_ARCH_ALLOC_PAGE
+
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 /* to align the pointer to the (next) page boundary */
diff --git a/include/asm-s390/system.h b/include/asm-s390/system.h
index c819ae25a842..e0d4500d5f95 100644
--- a/include/asm-s390/system.h
+++ b/include/asm-s390/system.h
@@ -116,6 +116,12 @@ extern void pfault_fini(void);
 #define pfault_fini()           do { } while (0)
 #endif /* CONFIG_PFAULT */
 
+#ifdef CONFIG_PAGE_STATES
+extern void cmma_init(void);
+#else
+static inline void cmma_init(void) { }
+#endif
+
 #define finish_arch_switch(prev) do {                                        \
         set_fs(current->thread.mm_segment);                                  \
         account_vtime(prev);                                                 \