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SubjectRe: [PATCH -v2 1/2] x86: Reserve [0xa0000, 0x100000] in e820 map
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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?

> 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?

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

Bjorn

> sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
> }
>
> @@ -1052,20 +1052,3 @@ void __init setup_arch(char **cmdline_p)
>
> mcheck_init();
> }
> -
> -#ifdef CONFIG_X86_32
> -
> -static struct resource video_ram_resource = {
> - .name = "Video RAM area",
> - .start = 0xa0000,
> - .end = 0xbffff,
> - .flags = IORESOURCE_BUSY | IORESOURCE_MEM
> -};
> -
> -void __init i386_reserve_resources(void)
> -{
> - request_resource(&iomem_resource, &video_ram_resource);
> - reserve_standard_io_resources();
> -}
> -
> -#endif /* CONFIG_X86_32 */



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