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

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Date:   Fri, 16 Jun 2017 18:16:02 +0200
From:   Jiri Bohac <jbohac@...e.cz>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] x86: fix lower bound of crash kernel low reservation

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@...e.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@...e.cz>
SUSE Labs, Prague, Czechia