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SubjectRe: [PATCH -v2 1/2] x86: Reserve [0xa0000, 0x100000] in e820 map
On 04/13/2010 02:02 PM, Bjorn Helgaas wrote:
> On Mon, 2010-04-12 at 15:32 -0700, Yinghai wrote:
>> Update e820 at first, and later put them resource tree.
>>
>> -V2: reserved that early, no PCI BAR can use it, force them to get new one
>>
>> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>> Cc: Guenter Roeck <guenter.roeck@ericsson.com>
>> Cc: Andy Isaacson <adi@hexapodia.org>
>> Tested-by: Andy Isaacson <adi@hexapodia.org>
>> Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
>> Acked-by: H. Peter Anvin <hpa@zytor.com>
>>
>> ---
>> arch/x86/include/asm/setup.h | 1 -
>> arch/x86/kernel/head32.c | 1 -
>> arch/x86/kernel/setup.c | 19 +------------------
>> 3 files changed, 1 insertion(+), 20 deletions(-)
>>
>> Index: linux-2.6/arch/x86/include/asm/setup.h
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/include/asm/setup.h
>> +++ linux-2.6/arch/x86/include/asm/setup.h
>> @@ -44,7 +44,6 @@ static inline void visws_early_detect(vo
>> extern unsigned long saved_video_mode;
>>
>> extern void reserve_standard_io_resources(void);
>> -extern void i386_reserve_resources(void);
>> extern void setup_default_timer_irq(void);
>>
>> #ifdef CONFIG_X86_MRST
>> Index: linux-2.6/arch/x86/kernel/head32.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/head32.c
>> +++ linux-2.6/arch/x86/kernel/head32.c
>> @@ -22,7 +22,6 @@ static void __init i386_default_early_se
>> {
>> /* Initilize 32bit specific setup functions */
>> x86_init.resources.probe_roms = probe_roms;
>> - x86_init.resources.reserve_resources = i386_reserve_resources;
>> x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
>>
>> reserve_ebda_region();
>
> I like the fact that this makes x86_64 and x86_32 handle the legacy VGA
> framebuffer the same way.
>
> What about arch/x86/kernel/probe_roms_32.c? That deals with expansion
> ROMs in the 0xc0000-0xfffff range, including the VGA ROM. We only build
> it for x86_32; is that correct, or should it be unified, too?

looks that file could be dropped.

We already put 0xa0000 - 0x100000 to reserved region.

>
>> Index: linux-2.6/arch/x86/kernel/setup.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/setup.c
>> +++ linux-2.6/arch/x86/kernel/setup.c
>> @@ -693,7 +693,7 @@ static void __init trim_bios_range(void)
>> * area (640->1Mb) as ram even though it is not.
>> * take them out.
>> */
>> - e820_remove_range(BIOS_BEGIN, BIOS_END - BIOS_BEGIN, E820_RAM, 1);
>> + e820_add_region(BIOS_BEGIN, BIOS_END - BIOS_BEGIN, E820_RESERVED);
>
> Let me see if I understand this. On Andy's machine, the e820 map
> doesn't mention the 0xa0000-0xf0000 range at all:
>
> BIOS-e820: 0000000000000000 - 000000000009ec00 (usable)
> BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
>
> e820_reserve_resources() inserts resources for some e820 entries (those
> that start before 0x100000 or are not E820_RESERVED). Andy's machine
> didn't supply any e820 entries that cover 0xa0000-0xf0000, so we didn't
> insert any resources there, and PCI assumed that range was available.
>
> This patch adds the [0xa0000-0x100000] range as E820_RESERVED. Since
> that starts below 0x100000, e820_reserve_resources() will insert a
> corresponding resource marked as BUSY.
>
> Then the second patch prevents PCI from using that BUSY region to
> allocate resources to devices.
>
> Is my understanding correct?

yes.

>
> I don't feel like I know enough about x86 architecture to ack this
> patch, but I don't object to it.

Thanks

Yinghai


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