From: Alexander van Heukelum <heukelum@mailshack.com>
To: Ingo Molnar <mingo@elte.hu>, Ian Campbell <ijc@hellion.org.uk>
Cc: Alexander van Heukelum <heukelum@fastmail.fm>,
"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Mark McLoughlin <markmc@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: [RFC] use realmode code to reserve end-of-conventional-memory to 1MB
Date: Thu, 28 Feb 2008 14:28:23 +0100 [thread overview]
Message-ID: <20080228132822.GA25278@mailshack.com> (raw)
In-Reply-To: <20080228131341.GA25213@mailshack.com>
Instead of using early reservations inside the kernel code,
we could use the realmode code to modify the e820 memmap.
This patch shows what that would look like. I have not looked
at the case where the BIOS does not provide an e820 memmap
yet. Probably a full solution would need to create a fake
e820 memmap in that case.
Comments?
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index e77d89f..522920a 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.c
@@ -23,6 +23,7 @@ static int detect_memory_e820(void)
int count = 0;
u32 next = 0;
u32 size, id;
+ u32 lowmem, ebda_addr;
u8 err;
struct e820entry *desc = boot_params.e820_map;
@@ -50,13 +51,51 @@ static int detect_memory_e820(void)
just return failure. */
if (id != SMAP) {
count = 0;
- break;
+ goto out;
}
count++;
desc++;
- } while (next && count < E820MAX);
-
+ } while (next && count < (E820MAX - 1));
+
+ /* Some BIOSes do not reserve the EBDA/XBDA area correctly in.
+ The e820-map. Find out where the EBDA resides by looking at
+ the BIOS data area and reserve the EBDA and the following
+ legacy adapter area explicitly. */
+#define BIOS_EBDA_SEGMENT 0x40E
+#define BIOS_LOWMEM_KILOBYTES 0x413
+
+ /* end of low (conventional) memory */
+ set_fs(0);
+ lowmem = rdfs16(BIOS_LOWMEM_KILOBYTES);
+ lowmem <<= 10;
+
+ /* start of EBDA area */
+ ebda_addr = rdfs16(BIOS_EBDA_SEGMENT);
+ ebda_addr <<= 4;
+
+ /* Fixup: bios puts an EBDA in the top 64K segment */
+ /* of conventional memory, but does not adjust lowmem. */
+ if ((lowmem - ebda_addr) <= 0x10000)
+ lowmem = ebda_addr;
+
+ /* Fixup: bios does not report an EBDA at all. */
+ /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */
+ if ((ebda_addr == 0) && (lowmem >= 0x9f000))
+ lowmem = 0x9f000;
+
+ /* Paranoia: should never happen, but... */
+ if (lowmem >= 0x100000)
+ lowmem = 0xa0000;
+
+ /* reserve all memory between lowmem and the 1MB mark */
+ desc->addr = lowmem;
+ desc->size = 0x100000 - lowmem;
+ desc->type = E820_RESERVED;
+ count++;
+ desc++;
+
+out:
return boot_params.e820_entries = count;
}
next prev parent reply other threads:[~2008-02-28 13:32 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-24 17:46 [PATCH] Fix alignment of early reservation for EBDA Alexander van Heukelum
2008-02-24 19:27 ` Andi Kleen
2008-02-24 19:41 ` Ingo Molnar
2008-02-24 20:53 ` Alexander van Heukelum
2008-02-25 2:18 ` H. Peter Anvin
2008-02-25 16:54 ` Alexander van Heukelum
2008-02-25 17:01 ` Ingo Molnar
2008-02-25 18:07 ` [PATCH] reserve_early end-of-conventional-memory to 1MB Alexander van Heukelum
2008-02-25 18:13 ` H. Peter Anvin
2008-02-25 19:46 ` Alexander van Heukelum
2008-02-25 21:17 ` H. Peter Anvin
2008-02-26 9:30 ` Ingo Molnar
2008-02-27 14:26 ` Andi Kleen
2008-02-27 14:38 ` [PATCH] reserve_early end-of-conventional-memory to 1MB II - some numbers to put it into perspective Andi Kleen
2008-02-27 16:44 ` H. Peter Anvin
2008-02-27 20:01 ` Alexander van Heukelum
2008-02-28 13:13 ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit Alexander van Heukelum
2008-02-28 13:28 ` Alexander van Heukelum [this message]
2008-02-28 21:12 ` [RFC] use realmode code to reserve end-of-conventional-memory to 1MB Ian Campbell
2008-02-28 21:14 ` H. Peter Anvin
2008-02-28 23:16 ` Ian Campbell
2008-02-29 20:00 ` Ingo Molnar
2008-03-04 11:41 ` Mark McLoughlin
2008-03-04 14:33 ` Ingo Molnar
2008-03-04 15:12 ` Ian Campbell
2008-03-04 15:13 ` Jeremy Fitzhardinge
2008-03-04 15:25 ` Ingo Molnar
2008-03-04 16:02 ` Jeremy Fitzhardinge
2008-03-04 16:15 ` Ingo Molnar
2008-03-04 16:15 ` Mark McLoughlin
2008-03-04 16:23 ` Ingo Molnar
2008-03-04 17:44 ` Jeremy Fitzhardinge
2008-03-05 15:59 ` Eduardo Habkost
2008-03-05 16:08 ` H. Peter Anvin
2008-03-05 16:53 ` Eduardo Habkost
2008-03-05 17:28 ` H. Peter Anvin
2008-03-05 17:28 ` Jeremy Fitzhardinge
2008-03-05 17:38 ` H. Peter Anvin
2008-03-05 16:38 ` Jeremy Fitzhardinge
2008-03-05 17:27 ` H. Peter Anvin
2008-02-28 21:09 ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit Ian Campbell
2008-02-29 11:49 ` Alexander van Heukelum
2008-02-29 17:14 ` Mark McLoughlin
2008-02-29 18:38 ` Alexander van Heukelum
2008-02-29 18:44 ` H. Peter Anvin
2008-02-29 18:56 ` Alexander van Heukelum
2008-02-29 22:06 ` Mark McLoughlin
2008-02-29 22:26 ` Alexander van Heukelum
2008-03-01 16:09 ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 Alexander van Heukelum
2008-03-01 16:12 ` [PATCH] reserve end-of-conventional-memory to 1MB on 64-bit add-on Alexander van Heukelum
2008-03-04 11:44 ` [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 Mark McLoughlin
2008-03-04 13:31 ` Alexander van Heukelum
2008-03-04 14:49 ` Ingo Molnar
2008-03-04 15:16 ` Mark McLoughlin
2008-03-04 15:24 ` Ingo Molnar
2008-03-04 15:18 ` Jeremy Fitzhardinge
2008-03-04 16:51 ` Alexander van Heukelum
2008-03-04 17:05 ` H. Peter Anvin
2008-03-04 17:11 ` Jeremy Fitzhardinge
2008-03-04 18:57 ` [PATCH] reserve end-of-conventional-memory to 1MB, 32-bit, use paravirt_enabled Alexander van Heukelum
2008-03-04 19:12 ` [PATCH] reserve end-of-conventional-memory to 1MB, 64-bit, " Alexander van Heukelum
2008-02-27 14:25 ` [PATCH] Fix alignment of early reservation for EBDA Andi Kleen
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