[PATCH] x86: fix lower bound of crash kernel low reservation

[PATCH] x86: fix lower bound of crash kernel low reservation

[Jiri Bohac]

Commit 0212f9159694 (x86: Add Crash kernel low reservation)
introduced reserve_crashkernel_low. This is used to reserve
crash kernel memory either if crashkernel=size,low is given
on the command line or if the region reserved by
reserve_crashkernel is entirely above 4G.

reserve_crashkernel_low tries to find a block of low_size bytes.
But there seems to be no good reason to restrict the lower bound
of the range to low_size. 

Make memblock_find_in_range search from the start of memory.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
---
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f81823695014..65622f07e633 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -503,7 +503,7 @@ static int __init reserve_crashkernel_low(void)
 			return 0;
 	}
 
-	low_base = memblock_find_in_range(low_size, 1ULL << 32, low_size, CRASH_ALIGN);
+	low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
 	if (!low_base) {
 		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
 		       (unsigned long)(low_size >> 20));

-- 
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia

[tip:x86/boot] x86/debug: Extend the lower bound of crash kernel low reservations

[tip-bot for Jiri Bohac]

Commit-ID:  fe2d48b805d01e14ddb8144de01de43171eb516f
Gitweb:     http://git.kernel.org/tip/fe2d48b805d01e14ddb8144de01de43171eb516f
Author:     Jiri Bohac <jbohac@suse.cz>
AuthorDate: Fri, 16 Jun 2017 18:16:02 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 22 Jun 2017 11:10:23 +0200

x86/debug: Extend the lower bound of crash kernel low reservations

The following change in 2013:

  0212f9159694 ("x86: Add Crash kernel low reservation")

... introduced reserve_crashkernel_low(). This function is used to
reserve crash kernel memory either if crashkernel=size,low is given
on the command line or if the region reserved by reserve_crashkernel
is entirely above 4G.

reserve_crashkernel_low() tries to find a block of 'low_size' bytes.
But there seems to be no good reason to restrict the lower bound
of the range to 'low_size'.

Make memblock_find_in_range() search from the start of memory.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/20170616161602.2r7birrf2y3ylv6v@dwarf.suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0b4d3c6..848d048 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -503,7 +503,7 @@ static int __init reserve_crashkernel_low(void)
 			return 0;
 	}
 
-	low_base = memblock_find_in_range(low_size, 1ULL << 32, low_size, CRASH_ALIGN);
+	low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
 	if (!low_base) {
 		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
 		       (unsigned long)(low_size >> 20));