[S390] hibernation: fix register corruption on machine checks

swsusp_arch_suspend() actually saves all cpu register contents on
hibernation.
Machine checks must be disabled since swsusp_arch_suspend() stores
register contents to their lowcore save areas. That's the same
place where register contents on machine checks would be saved.
To avoid register corruption disable machine checks.
We must also disable machine checks in the new psw mask for
program checks, since swsusp_arch_suspend() may generate program
checks.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 24 insertions, 12 deletions

diff --git a/arch/s390/power/swsusp.c b/arch/s390/power/swsusp.c
index e6a4fe9..bd1f5c6 100644
--- a/arch/s390/power/swsusp.c
+++ b/arch/s390/power/swsusp.c
@@ -7,24 +7,36 @@
  *
  */
 
+#include <asm/system.h>
 
-/*
- * save CPU registers before creating a hibernation image and before
- * restoring the memory state from it
- */
 void save_processor_state(void)
 {
-	/* implentation contained in the
-	 * swsusp_arch_suspend function
+	/* swsusp_arch_suspend() actually saves all cpu register contents.
+	 * Machine checks must be disabled since swsusp_arch_suspend() stores
+	 * register contents to their lowcore save areas. That's the same
+	 * place where register contents on machine checks would be saved.
+	 * To avoid register corruption disable machine checks.
+	 * We must also disable machine checks in the new psw mask for
+	 * program checks, since swsusp_arch_suspend() may generate program
+	 * checks. Disabling machine checks for all other new psw masks is
+	 * just paranoia.
 	 */
+	local_mcck_disable();
+	/* Disable lowcore protection */
+	__ctl_clear_bit(0,28);
+	S390_lowcore.external_new_psw.mask &= ~PSW_MASK_MCHECK;
+	S390_lowcore.svc_new_psw.mask &= ~PSW_MASK_MCHECK;
+	S390_lowcore.io_new_psw.mask &= ~PSW_MASK_MCHECK;
+	S390_lowcore.program_new_psw.mask &= ~PSW_MASK_MCHECK;
 }
 
-/*
- * restore the contents of CPU registers
- */
 void restore_processor_state(void)
 {
-	/* implentation contained in the
-	 * swsusp_arch_resume function
-	 */
+	S390_lowcore.external_new_psw.mask |= PSW_MASK_MCHECK;
+	S390_lowcore.svc_new_psw.mask |= PSW_MASK_MCHECK;
+	S390_lowcore.io_new_psw.mask |= PSW_MASK_MCHECK;
+	S390_lowcore.program_new_psw.mask |= PSW_MASK_MCHECK;
+	/* Enable lowcore protection */
+	__ctl_set_bit(0,28);
+	local_mcck_enable();
 }