From: Martin Schwidefsky <[email protected]>
From: Hubertus Franke <[email protected]>
From: Himanshu Raj <[email protected]>
[patch 2/9] Guest page hinting: unused / free pages on s390.
s390 uses the milli-coded ESSA instruction to set the page state. The
page state is formed by four guest page states called block usage states
and three host page states called block content states.
This patch uses none of the host states and only two of the guest states:
- stable (S): there is essential content in the page
- unused (U): there is no usefull content and any access to the page will
cause an addressing exception.
Since the access of unused pages causes addressing exceptions we need
to take care with /dev/mem. The copy_{from_to}_user functions need to
be able to cope with addressing exceptions for the kernel address space.
Signed-off-by: Martin Schwidefsky <[email protected]>
---
arch/s390/Kconfig | 3 ++
arch/s390/kernel/head64.S | 10 +++++++
arch/s390/lib/uaccess.S | 18 ++++++++-----
arch/s390/lib/uaccess64.S | 18 ++++++++-----
include/asm-s390/page-states.h | 55 +++++++++++++++++++++++++++++++++++++++++
include/asm-s390/setup.h | 1
6 files changed, 93 insertions(+), 12 deletions(-)
diff -urpN linux-2.6/arch/s390/Kconfig linux-2.6-patched/arch/s390/Kconfig
--- linux-2.6/arch/s390/Kconfig 2006-09-01 12:49:25.000000000 +0200
+++ linux-2.6-patched/arch/s390/Kconfig 2006-09-01 12:49:36.000000000 +0200
@@ -463,6 +463,9 @@ config KEXEC
current kernel, and to start another kernel. It is like a reboot
but is independent of hardware/microcode support.
+config PAGE_STATES
+ bool "Enable support for guest page hinting."
+
endmenu
source "net/Kconfig"
diff -urpN linux-2.6/arch/s390/kernel/head64.S linux-2.6-patched/arch/s390/kernel/head64.S
--- linux-2.6/arch/s390/kernel/head64.S 2006-09-01 12:49:25.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/head64.S 2006-09-01 12:49:36.000000000 +0200
@@ -240,6 +240,16 @@ startup_continue:
oi 7(%r12),0x80 # set IDTE flag
0:
+#
+# find out if we have the ESSA instruction
+#
+ la %r1,0f-.LPG1(%r13) # set program check address
+ stg %r1,__LC_PGM_NEW_PSW+8
+ lghi %r1,0
+ .long 0xb9ab0001 # essa get state
+ oi 6(%r12),0x01 # set ESSA flag
+0:
+
lpswe .Lentry-.LPG1(13) # jump to _stext in primary-space,
# virtual and never return ...
.align 16
diff -urpN linux-2.6/arch/s390/lib/uaccess64.S linux-2.6-patched/arch/s390/lib/uaccess64.S
--- linux-2.6/arch/s390/lib/uaccess64.S 2006-09-01 12:49:25.000000000 +0200
+++ linux-2.6-patched/arch/s390/lib/uaccess64.S 2006-09-01 12:49:36.000000000 +0200
@@ -20,14 +20,14 @@
__copy_from_user_asm:
slgr %r0,%r0
0: mvcp 0(%r3,%r2),0(%r4),%r0
- jnz 1f
+7: jnz 1f
slgr %r2,%r2
br %r14
1: la %r2,256(%r2)
la %r4,256(%r4)
aghi %r3,-256
2: mvcp 0(%r3,%r2),0(%r4),%r0
- jnz 1b
+8: jnz 1b
3: slgr %r2,%r2
br %r14
4: lghi %r0,-4096
@@ -39,13 +39,16 @@ __copy_from_user_asm:
jnh 6f # no, the current page faulted
# move with the reduced length which is < 256
5: mvcp 0(%r5,%r2),0(%r4),%r0
- slgr %r3,%r5
+9: slgr %r3,%r5
6: lgr %r2,%r3
br %r14
.section __ex_table,"a"
.quad 0b,4b
.quad 2b,4b
.quad 5b,6b
+ .quad 7b,6b
+ .quad 8b,6b
+ .quad 9b,6b
.previous
.align 4
@@ -55,14 +58,14 @@ __copy_from_user_asm:
__copy_to_user_asm:
slgr %r0,%r0
0: mvcs 0(%r3,%r4),0(%r2),%r0
- jnz 1f
+7: jnz 1f
slgr %r2,%r2
br %r14
1: la %r2,256(%r2)
la %r4,256(%r4)
aghi %r3,-256
2: mvcs 0(%r3,%r4),0(%r2),%r0
- jnz 1b
+8: jnz 1b
3: slgr %r2,%r2
br %r14
4: lghi %r0,-4096
@@ -74,13 +77,16 @@ __copy_to_user_asm:
jnh 6f # no, the current page faulted
# move with the reduced length which is < 256
5: mvcs 0(%r5,%r4),0(%r2),%r0
- slgr %r3,%r5
+9: slgr %r3,%r5
6: lgr %r2,%r3
br %r14
.section __ex_table,"a"
.quad 0b,4b
.quad 2b,4b
.quad 5b,6b
+ .quad 7b,6b
+ .quad 8b,6b
+ .quad 9b,6b
.previous
.align 4
diff -urpN linux-2.6/arch/s390/lib/uaccess.S linux-2.6-patched/arch/s390/lib/uaccess.S
--- linux-2.6/arch/s390/lib/uaccess.S 2006-09-01 12:49:25.000000000 +0200
+++ linux-2.6-patched/arch/s390/lib/uaccess.S 2006-09-01 12:49:36.000000000 +0200
@@ -20,14 +20,14 @@
__copy_from_user_asm:
slr %r0,%r0
0: mvcp 0(%r3,%r2),0(%r4),%r0
- jnz 1f
+7: jnz 1f
slr %r2,%r2
br %r14
1: la %r2,256(%r2)
la %r4,256(%r4)
ahi %r3,-256
2: mvcp 0(%r3,%r2),0(%r4),%r0
- jnz 1b
+8: jnz 1b
3: slr %r2,%r2
br %r14
4: lhi %r0,-4096
@@ -39,13 +39,16 @@ __copy_from_user_asm:
jnh 6f # no, the current page faulted
# move with the reduced length which is < 256
5: mvcp 0(%r5,%r2),0(%r4),%r0
- slr %r3,%r5
+9: slr %r3,%r5
6: lr %r2,%r3
br %r14
.section __ex_table,"a"
.long 0b,4b
.long 2b,4b
.long 5b,6b
+ .long 7b,6b
+ .long 8b,6b
+ .long 9b,6b
.previous
.align 4
@@ -55,14 +58,14 @@ __copy_from_user_asm:
__copy_to_user_asm:
slr %r0,%r0
0: mvcs 0(%r3,%r4),0(%r2),%r0
- jnz 1f
+7: jnz 1f
slr %r2,%r2
br %r14
1: la %r2,256(%r2)
la %r4,256(%r4)
ahi %r3,-256
2: mvcs 0(%r3,%r4),0(%r2),%r0
- jnz 1b
+8: jnz 1b
3: slr %r2,%r2
br %r14
4: lhi %r0,-4096
@@ -74,13 +77,16 @@ __copy_to_user_asm:
jnh 6f # no, the current page faulted
# move with the reduced length which is < 256
5: mvcs 0(%r5,%r4),0(%r2),%r0
- slr %r3,%r5
+9: slr %r3,%r5
6: lr %r2,%r3
br %r14
.section __ex_table,"a"
.long 0b,4b
.long 2b,4b
.long 5b,6b
+ .long 7b,6b
+ .long 8b,6b
+ .long 9b,6b
.previous
.align 4
diff -urpN linux-2.6/include/asm-s390/page-states.h linux-2.6-patched/include/asm-s390/page-states.h
--- linux-2.6/include/asm-s390/page-states.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6-patched/include/asm-s390/page-states.h 2006-09-01 12:49:36.000000000 +0200
@@ -0,0 +1,55 @@
+#ifndef _ASM_S390_PAGE_STATES_H
+#define _ASM_S390_PAGE_STATES_H
+
+#define ESSA_GET_STATE 0
+#define ESSA_SET_STABLE 1
+#define ESSA_SET_UNUSED 2
+#define ESSA_SET_VOLATILE 3
+#define ESSA_SET_PVOLATILE 4
+#define ESSA_SET_STABLE_MAKE_RESIDENT 5
+#define ESSA_SET_STABLE_IF_NOT_DISCARDED 6
+
+#define ESSA_USTATE_MASK 0x0c
+#define ESSA_USTATE_STABLE 0x00
+#define ESSA_USTATE_UNUSED 0x04
+#define ESSA_USTATE_PVOLATILE 0x08
+#define ESSA_USTATE_VOLATILE 0x0c
+
+#define ESSA_CSTATE_MASK 0x03
+#define ESSA_CSTATE_RESIDENT 0x00
+#define ESSA_CSTATE_PRESERVED 0x02
+#define ESSA_CSTATE_ZERO 0x03
+
+extern struct page *mem_map;
+
+/*
+ * ESSA <rc-reg>,<page-address-reg>,<command-immediate>
+ */
+#define page_essa(_page,_command) ({ \
+ int _rc; \
+ asm volatile(".insn rrf,0xb9ab0000,%0,%1,%2,0" \
+ : "=&d" (_rc) : "a" (((_page)-mem_map)<<PAGE_SHIFT), \
+ "i" (_command)); \
+ _rc; \
+})
+
+static inline void page_set_unused(struct page *page, int order)
+{
+ int i;
+
+ if (!MACHINE_HAS_ESSA)
+ return;
+ for (i = 0; i < (1 << order); i++)
+ page_essa(page + i, ESSA_SET_UNUSED);
+}
+
+static inline void page_set_stable(struct page *page, int order)
+{
+ int i;
+
+ if (!MACHINE_HAS_ESSA)
+ return;
+ for (i = 0; i < (1 << order); i++)
+ page_essa(page + i, ESSA_SET_STABLE);
+}
+#endif /* _ASM_S390_PAGE_STATES_H */
diff -urpN linux-2.6/include/asm-s390/setup.h linux-2.6-patched/include/asm-s390/setup.h
--- linux-2.6/include/asm-s390/setup.h 2006-09-01 12:49:32.000000000 +0200
+++ linux-2.6-patched/include/asm-s390/setup.h 2006-09-01 12:49:36.000000000 +0200
@@ -39,6 +39,7 @@ extern unsigned long machine_flags;
#define MACHINE_IS_P390 (machine_flags & 4)
#define MACHINE_HAS_MVPG (machine_flags & 16)
#define MACHINE_HAS_IDTE (machine_flags & 128)
+#define MACHINE_HAS_ESSA (machine_flags & 256)
#ifndef __s390x__
#define MACHINE_HAS_IEEE (machine_flags & 2)
-
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