Re: Regression in 2.6.23-pre Was: Problems with 2.6.23-rc6 on AMD Geode LX800

["H. Peter Anvin" <hpa@zytor.com>]

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Jordan Crouse wrote:
> 
> Hmm - the old code seems to fail to e801 when CF was set too:
> 
> 	int     $0x15                           # make the call
> 	jc      bail820                         # fall to e801 if it fails
> 
> 	cmpl    $SMAP, %eax                     # check the return is `SMAP'
> 	jne     bail820                         # fall to e801 if it fails
> 
> Thats not to say that the old code was correct, mind you.  Failing on a
> bad ID and returning without error on a set CF seems to be good to me.
> 

Testing this patch now:


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>From 2efa33f81ef56e7700c09a3d8a881c96692149e5 Mon Sep 17 00:00:00 2001
From: H. Peter Anvin <hpa@zytor.com>
Date: Wed, 26 Sep 2007 14:11:43 -0700
Subject: [PATCH] [x86 setup] Handle case of improperly terminated E820 chain

At least one system (a Geode system with a Digital Logic BIOS) has
been found which suddenly stops reporting the SMAP signature when
reading the E820 memory chain.  We can't know what, exactly, broke in
the BIOS, so if we detect this situation, declare the E820 data
unusable and fall back to E801.

Also, revert to original behavior of always probing all memory
methods; that way all the memory information is available to the
kernel.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Jordan Crouse <jordan.crouse@amd.com>
Cc: Joerg Pommnitz <pommnitz@yahoo.com>
---
 arch/i386/boot/memory.c |   30 +++++++++++++++++++++++-------
 1 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/arch/i386/boot/memory.c b/arch/i386/boot/memory.c
index 1a2e62d..bccaa1c 100644
--- a/arch/i386/boot/memory.c
+++ b/arch/i386/boot/memory.c
@@ -20,6 +20,7 @@
 
 static int detect_memory_e820(void)
 {
+	int count = 0;
 	u32 next = 0;
 	u32 size, id;
 	u8 err;
@@ -33,14 +34,24 @@ static int detect_memory_e820(void)
 		      "=m" (*desc)
 		    : "D" (desc), "a" (0xe820));
 
-		if (err || id != SMAP)
+		/* Some BIOSes stop returning SMAP in the middle of
+		   the search loop.  We don't know exactly how the BIOS
+		   screwed up the map at that point, we might have a
+		   partial map, the full map, or complete garbage, so
+		   just return failure. */
+		if (id != SMAP) {
+			count = 0;
 			break;
+		}
 
-		boot_params.e820_entries++;
+		if (err)
+			break;
+
+		count++;
 		desc++;
-	} while (next && boot_params.e820_entries < E820MAX);
+	} while (next && count < E820MAX);
 
-	return boot_params.e820_entries;
+	return boot_params.e820_entries = count;
 }
 
 static int detect_memory_e801(void)
@@ -89,11 +100,16 @@ static int detect_memory_88(void)
 
 int detect_memory(void)
 {
+	int err = -1;
+
 	if (detect_memory_e820() > 0)
-		return 0;
+		err = 0;
 
 	if (!detect_memory_e801())
-		return 0;
+		err = 0;
+
+	if (!detect_memory_88())
+		err = 0;
 
-	return detect_memory_88();
+	return err;
 }
-- 
1.5.3.1