[PATCH 4.19 280/346] s390/kexec_file: fix diag308 subcode when loading crash kernel

Greg Kroah-Hartman
2020-12-28T13:34:24Z

From: Philipp Rudo <prudo@linux.ibm.com>

commit 613775d62ec60202f98d2c5f520e6e9ba6dd4ac4 upstream.

diag308 subcode 0 performes a clear reset which inlcudes the reset of
all registers in the system. While this is the preferred behavior when
loading a normal kernel via kexec it prevents the crash kernel to store
the register values in the dump. To prevent this use subcode 1 when
loading a crash kernel instead.

Fixes: ee337f5469fd ("s390/kexec_file: Add crash support to image loader")
Cc: <stable@vger.kernel.org> # 4.17
Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
Reported-by: Xiaoying Yan <yiyan@redhat.com>
Tested-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/purgatory/head.S | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/arch/s390/purgatory/head.S
+++ b/arch/s390/purgatory/head.S
@@ -61,14 +61,15 @@
jh 10b
.endm

-.macro START_NEXT_KERNEL base
+.macro START_NEXT_KERNEL base subcode
lg %r4,kernel_entry-\base(%r13)
lg %r5,load_psw_mask-\base(%r13)
ogr %r4,%r5
stg %r4,0(%r0)

xgr %r0,%r0
- diag %r0,%r0,0x308
+ lghi %r1,\subcode
+ diag %r0,%r1,0x308
.endm

.text
@@ -123,7 +124,7 @@ ENTRY(purgatory_start)
je .start_crash_kernel

/* start normal kernel */
- START_NEXT_KERNEL .base_crash
+ START_NEXT_KERNEL .base_crash 0

.return_old_kernel:
lmg %r6,%r15,gprregs-.base_crash(%r13)
@@ -227,7 +228,7 @@ ENTRY(purgatory_start)
MEMCPY %r9,%r10,%r11

/* start crash kernel */
- START_NEXT_KERNEL .base_dst
+ START_NEXT_KERNEL .base_dst 1