Re: [LinuxBIOS] [PATCH] e820 table correction

[yhlu]

commit dbf9272e863bf4b17ee8e3c66c26682b2061d40d
Author: Andi Kleen 
Date:   Tue Sep 26 10:52:36 2006 +0200

[PATCH] Don't force reserve the 640k-1MB range

From i386 x86-64 inherited code to force reserve the 640k-1MB area.
    That was needed on some old systems.

But we generally trust the e820 map to be correct on 64bit systems
    and mark all areas that are not memory correctly.

This patch will allow to use the real memory in there.

Or rather the only way to find out if it's still needed is to
    try. So far I'm optimistic.

Signed-off-by: Andi Kleen

diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index 164d0b8..e06c271 100644
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -71,12 +71,7 @@ static inline int bad_addr(unsigned long *addrp,
unsigned long size)
    	return 1;
    }
 #endif
-	/* kernel code + 640k memory hole (later should not be needed, but
-	   be paranoid for now) */
-	if (last >= 640*1024 && addr < 1024*1024) {
-		*addrp = 1024*1024;
-		return 1;
-	}
+	/* kernel code */
    if (last >= __pa_symbol(&_text) && last < __pa_symbol(&_end)) {
    	*addrp = __pa_symbol(&_end);
    	return 1;
@@ -519,13 +514,6 @@ static int __init sanitize_e820_map(struct
e820entry * biosmap, char * pnr_map)
  * If we're lucky and live on a modern system, the setup code
  * will have given us a memory map that we can use to properly
  * set up memory.  If we aren't, we'll fake a memory map.
- *
- * We check to see that the memory map contains at least 2 elements
- * before we'll use it, because the detection code in setup.S may
- * not be perfect and most every PC known to man has two memory
- * regions: one from 0 to 640k, and one from 1mb up.  (The IBM
- * thinkpad 560x, for example, does not cooperate with the memory
- * detection code.)
  */
 static int __init copy_e820_map(struct e820entry * biosmap, int nr_map)
 {
@@ -543,25 +531,6 @@ static int __init copy_e820_map(struct e820entry
* biosmap, int nr_map)
    	if (start > end)
    		return -1;

-		/*
-		 * Some BIOSes claim RAM in the 640k - 1M region.
-		 * Not right. Fix it up.
-		 *
-		 * This should be removed on Hammer which is supposed to not
-		 * have non e820 covered ISA mappings there, but I had some strange
-		 * problems so it stays for now.  -AK
-		 */
-		if (type == E820_RAM) {
-			if (start < 0x100000ULL && end > 0xA0000ULL) {
-				if (start < 0xA0000ULL)
-					add_memory_region(start, 0xA0000ULL-start, type);
-				if (end <= 0x100000ULL)
-					continue;
-				start = 0x100000ULL;
-				size = end - start;
-			}
-		}
-
    	add_memory_region(start, size, type);
    } while (biosmap++,--nr_map);
    return 0;

On 2/2/07, Andi Kleen  wrote:
> On Saturday 03 February 2007 01:17, Lu, Yinghai wrote:
> > Actually that is because of Andi's patch cause the problem.
>
> What patch?
>
> -Andi