The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6b4b54c7ca347bcb4aa7a3cc01aa16e84ac7fbe4 Mon Sep 17 00:00:00 2001 From: Alexander Egorenkov egorenar@linux.ibm.com Date: Wed, 9 Feb 2022 11:25:09 +0100 Subject: [PATCH] s390/setup: preserve memory at OLDMEM_BASE and OLDMEM_SIZE

We need to preserve the values at OLDMEM_BASE and OLDMEM_SIZE which are used by zgetdump in case when kdump crashes. In that case zgetdump will attempt to read OLDMEM_BASE and OLDMEM_SIZE in order to find out where the memory range [0 - OLDMEM_SIZE] belonging to the production kernel is.

Fixes: f1a546947431 ("s390/setup: don't reserve memory that occupied decompressor's head") Cc: stable@vger.kernel.org # 5.15+ Signed-off-by: Alexander Egorenkov egorenar@linux.ibm.com Acked-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index f2c25d113e7b..05327be3a982 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -800,6 +800,8 @@ static void __init check_initrd(void) static void __init reserve_kernel(void) { memblock_reserve(0, STARTUP_NORMAL_OFFSET); + memblock_reserve(OLDMEM_BASE, sizeof(unsigned long)); + memblock_reserve(OLDMEM_SIZE, sizeof(unsigned long)); memblock_reserve(__amode31_base, __eamode31 - __samode31); memblock_reserve(__pa(sclp_early_sccb), EXT_SCCB_READ_SCP); memblock_reserve(__pa(_stext), _end - _stext);