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Message-ID: <508E002B.4090200@teksavvy.com>
Date: Mon, 29 Oct 2012 00:03:55 -0400
From: Mark Lord <kernel@teksavvy.com>
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To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Regression from 3.4.9 to 3.4.16 "stable" kernel
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My server here runs the 3.4.xx series of "stable" kernels.
Until today, it was running 3.4.9.
Today I tried to upgrade it to 3.4.16.
It hangs in setup.c.

I've isolated the fault down to this specific change
that was made between 3.4.9 and 3.4.16.
Reverting this change allows the system to boot/run normally again.


--- linux-3.4.9/arch/x86/kernel/setup.c	2012-08-15 11:17:17.000000000 -0400
+++ linux-3.4.16/arch/x86/kernel/setup.c	2012-10-28 13:36:33.000000000 -0400
@@ -927,8 +927,21 @@

 #ifdef CONFIG_X86_64
 	if (max_pfn > max_low_pfn) {
-		max_pfn_mapped = init_memory_mapping(1UL<<32,
-						     max_pfn<<PAGE_SHIFT);
+		int i;
+		for (i = 0; i < e820.nr_map; i++) {
+			struct e820entry *ei = &e820.map[i];
+
+			if (ei->addr + ei->size <= 1UL << 32)
+				continue;
+
+			if (ei->type == E820_RESERVED)
+				continue;
+
+			max_pfn_mapped = init_memory_mapping(
+				ei->addr < 1UL << 32 ? 1UL << 32 : ei->addr,
+				ei->addr + ei->size);
+		}
+
 		/* can we preseve max_low_pfn ?*/
 		max_low_pfn = max_pfn;
 	}