linux-kernel - [PATCH 5.15 217/279] s390/setup: avoid reserving memory above identity mapping

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Message-Id: <20211124115726.246383184@linuxfoundation.org>
Date:   Wed, 24 Nov 2021 12:58:24 +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,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: [PATCH 5.15 217/279] s390/setup: avoid reserving memory above identity mapping

From: Vasily Gorbik <gor@...ux.ibm.com>

commit 420f48f636b98fd685f44a3acc4c0a7c0840910d upstream.

Such reserved memory region, if not cleaned up later causes problems when
memblock_free_all() is called to release free pages to the buddy allocator
and those reserved regions are carried over to reserve_bootmem_region()
which marks the pages as PageReserved.

Instead use memblock_set_current_limit() to make sure memblock allocations
do not go over identity mapping (which could happen when "mem=" option
is used or during kdump).

Cc: stable@...r.kernel.org
Fixes: 73045a08cf55 ("s390: unify identity mapping limits handling")
Reported-by: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
Reviewed-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/s390/kernel/setup.c |   10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -634,14 +634,6 @@ static struct notifier_block kdump_mem_n
 #endif
 
 /*
- * Make sure that the area above identity mapping is protected
- */
-static void __init reserve_above_ident_map(void)
-{
-	memblock_reserve(ident_map_size, ULONG_MAX);
-}
-
-/*
  * Reserve memory for kdump kernel to be loaded with kexec
  */
 static void __init reserve_crashkernel(void)
@@ -1005,11 +997,11 @@ void __init setup_arch(char **cmdline_p)
 	setup_control_program_code();
 
 	/* Do some memory reservations *before* memory is added to memblock */
-	reserve_above_ident_map();
 	reserve_kernel();
 	reserve_initrd();
 	reserve_certificate_list();
 	reserve_mem_detect_info();
+	memblock_set_current_limit(ident_map_size);
 	memblock_allow_resize();
 
 	/* Get information about *all* installed memory */