linux-kernel - [PATCH 5.4 348/453] s390/kexec_file: fix diag308 subcode when loading crash kernel

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Date:   Mon, 28 Dec 2020 13:49:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Philipp Rudo <prudo@...ux.ibm.com>,
        Xiaoying Yan <yiyan@...hat.com>,
        Lianbo Jiang <lijiang@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>
Subject: [PATCH 5.4 348/453] s390/kexec_file: fix diag308 subcode when loading crash kernel

From: Philipp Rudo <prudo@...ux.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@...r.kernel.org> # 4.17
Signed-off-by: Philipp Rudo <prudo@...ux.ibm.com>
Reported-by: Xiaoying Yan <yiyan@...hat.com>
Tested-by: Lianbo Jiang <lijiang@...hat.com>
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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
@@ -62,14 +62,15 @@
 	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
 
 
 load_psw_mask: