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SubjectRe: [PATCH -tip] x86,apic: Use PAGE_SIZE instead of numbers
On 11/08/2009 07:53 AM, Cyrill Gorcunov wrote:
> The whole page is reserved for IO-APIC fixmap
> due to non-cacheable requirement. So lets note
> this explicitly instead of playing with numbers.
>
> CC: Yinghai Lu <yinghai@kernel.org>
> CC: "Maciej W. Rozycki" <macro@linux-mips.org>
> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
> ---
>
> Perhaps I miss something and (4 * 1024) have some special
> meaning?
>
> arch/x86/kernel/apic/io_apic.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6.git/arch/x86/kernel/apic/io_apic.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/apic/io_apic.c
> +++ linux-2.6.git/arch/x86/kernel/apic/io_apic.c
> @@ -4144,7 +4144,7 @@ fake_ioapic_page:
> idx++;
>
> ioapic_res->start = ioapic_phys;
> - ioapic_res->end = ioapic_phys + (4 * 1024) - 1;
> + ioapic_res->end = ioapic_phys + PAGE_SIZE - 1;
> ioapic_res++;
> }
> }

In theory we could have more than one ioapic packed into a single page,
and it is also entirely plausible we'll support other page sizes in x86
at some point. However, it's probably easier to flag something as
PAGE_SIZE and have to fix it up later than have magic constants, so I
think it's probably the right thing to do.

-hpa


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