linux-kernel - [PATCH 5.16 117/186] s390/setup: preserve memory at OLDMEM_BASE and OLDMEM

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Date:   Mon,  7 Mar 2022 10:19:15 +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,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: [PATCH 5.16 117/186] s390/setup: preserve memory at OLDMEM_BASE and OLDMEM_SIZE

From: Alexander Egorenkov <egorenar@...ux.ibm.com>

commit 6b4b54c7ca347bcb4aa7a3cc01aa16e84ac7fbe4 upstream.

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@...r.kernel.org # 5.15+
Signed-off-by: Alexander Egorenkov <egorenar@...ux.ibm.com>
Acked-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/s390/kernel/setup.c |    2 ++
 1 file changed, 2 insertions(+)

--- 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);