linux-kernel - Re: [PATCH] x86: extend e820 ealy_res support 32bit

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Message-ID: <483EB18F.4070105@goop.org>
Date:	Thu, 29 May 2008 14:37:19 +0100
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: extend e820 ealy_res support 32bit - fix #2

Yinghai Lu wrote:
> can we use e820 entries for that? So the domain builder could have
> several entries for E820_RAM and E820_RESERVED...
>   

I tried this, but it doesn't work; the kernel crashes during boot, 
presumably because it's trying to use the reserved memory as heap.  I 
suspect the e820 maps are not registered early enough or something...

(One thought: if reserving in the E820 map were enough, then couldn't we 
use it for all the early reservations?)

I've attached the non-working patch below.

The working kernel reports:

(early) BIOS-provided physical RAM map:
(early)  Xen: 0000000000000000 - 000000000009f000 (usable)
(early)  Xen: 0000000000100000 - 0000000010000000 (usable)
(early) console [xenboot0] enabled
(early) debug: ignoring loglevel setting.
(early) 0MB HIGHMEM available.
(early) 256MB LOWMEM available.
(early)   low ram: 018fd000 - 10000000
(early)   bootmap 018fd000 - 018ff000
(early)   early res: 0 [0-fff] BIOS data page
(early)   early res: 1 [1000-1fff] EX TRAMPOLINE
(early)   early res: 2 [6000-6fff] TRAMPOLINE
(early)   early res: 3 [18aa000-18ecfff] XEN
(early)   early res: 4 [1000000-18a9303] TEXT DATA BSS
(early)   early res: 5 [18ed000-18fcfff] INIT_PG_TABLE
(early)   early res: 6 [18fd000-18fefff] BOOTMAP

But the non-working one says:

(early) BIOS-provided physical RAM map:
(early)  Xen: 0000000000000000 - 000000000009f000 (usable)
(early)  Xen: 0000000000100000 - 0000000010000000 (usable)
(early)  Xen: 00000000018aa000 - 00000000018ed000 (reserved)
(early) console [xenboot0] enabled
(early) debug: ignoring loglevel setting.
(early) 0MB HIGHMEM available.
(early) 256MB LOWMEM available.
(early)   low ram: 018fd000 - 10000000
(early)   bootmap 018fd000 - 018ff000
(early)   early res: 0 [0-fff] BIOS data page
(early)   early res: 1 [1000-1fff] EX TRAMPOLINE
(early)   early res: 2 [6000-6fff] TRAMPOLINE
(early)   early res: 3 [1000000-18a9303] TEXT DATA BSS
(early)   early res: 4 [18ed000-18fcfff] INIT_PG_TABLE
(early)   early res: 5 [18fd000-18fefff] BOOTMAP

	J

Subject: xen: reserve Xen-specific memory in e820 map

Make sure that the start_info and pfn->mfn translation array are reserved.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/xen/setup.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff -r ad372188bccf arch/x86/xen/setup.c
--- a/arch/x86/xen/setup.c	Thu May 29 13:56:09 2008 +0100
+++ b/arch/x86/xen/setup.c	Thu May 29 14:34:35 2008 +0100
@@ -40,9 +40,19 @@
 	max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
 
 	e820.nr_map = 0;
+
 	add_memory_region(0, LOWMEMSIZE(), E820_RAM);
 	add_memory_region(HIGH_MEMORY, PFN_PHYS(max_pfn)-HIGH_MEMORY, E820_RAM);
 
+	/*
+	 * Reserve Xen bits:
+	 *  - mfn_list
+	 *  - xen_start_info
+	 * See comment above "struct start_info" in <xen/interface/xen.h>
+	 */
+	add_memory_region(__pa(xen_start_info->mfn_list),
+			  xen_start_info->pt_base - xen_start_info->mfn_list,
+			  E820_RESERVED);
 	return "Xen";
 }
 


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