s390/hibernate: Save and restore absolute zero pages

Since commit 5f954c34 ([S390] hibernation: fix lowcore handling)
the absolute zero lowcore is lost during suspend/resume.
For example, this leads to the problem that the re-IPL device
for kdump is no longer set after resume.

With this patch during suspend a buffer is allocated in the new PM
notifier "suspend_pm_cb" and then the absolute zero lowcore is saved
to that buffer. The resume code then copies back this buffer to
absolute zero and afterwards the PM notifier releases the memory.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 26 insertions, 3 deletions

diff --git a/arch/s390/kernel/swsusp_asm64.S b/arch/s390/kernel/swsusp_asm64.S
index d4ca4e0617b5..c487be4cfc81 100644
--- a/arch/s390/kernel/swsusp_asm64.S
+++ b/arch/s390/kernel/swsusp_asm64.S
@@ -36,8 +36,8 @@ ENTRY(swsusp_arch_suspend)
         /* Store prefix register on stack */
         stpx    __SF_EMPTY(%r15)
 
-        /* Save prefix register contents for lowcore */
-        llgf    %r4,__SF_EMPTY(%r15)
+        /* Save prefix register contents for lowcore copy */
+        llgf    %r10,__SF_EMPTY(%r15)
 
         /* Get pointer to save area */
         lghi    %r1,0x1000
@@ -91,7 +91,18 @@ ENTRY(swsusp_arch_suspend)
         xc      __SF_EMPTY(4,%r15),__SF_EMPTY(%r15)
         spx     __SF_EMPTY(%r15)
 
+        /* Save absolute zero pages */
+        larl    %r2,suspend_zero_pages
+        lg      %r2,0(%r2)
+        lghi    %r4,0
+        lghi    %r3,2*PAGE_SIZE
+        lghi    %r5,2*PAGE_SIZE
+1:      mvcle   %r2,%r4,0
+        jo      1b
+
+        /* Copy lowcore to absolute zero lowcore */
         lghi    %r2,0
+        lgr     %r4,%r10
         lghi    %r3,2*PAGE_SIZE
         lghi    %r5,2*PAGE_SIZE
 1:      mvcle   %r2,%r4,0
@@ -248,8 +259,20 @@ restore_registers:
         /* Load old stack */
         lg      %r15,0x2f8(%r13)
 
+        /* Save prefix register */
+        mvc __SF_EMPTY(4,%r15),0x318(%r13)
+
+        /* Restore absolute zero pages */
+        lghi    %r2,0
+        larl    %r4,suspend_zero_pages
+        lg      %r4,0(%r4)
+        lghi    %r3,2*PAGE_SIZE
+        lghi    %r5,2*PAGE_SIZE
+1:      mvcle   %r2,%r4,0
+        jo      1b
+
         /* Restore prefix register */
-        spx     0x318(%r13)
+        spx     __SF_EMPTY(%r15)
 
         /* Activate DAT */
         stosm   __SF_EMPTY(%r15),0x04