RE: [PATCH] Enable K8 GART as an IOMMU

["Jan Beulich" <jbeulich@novell.com>]

>>> "Langsdorf, Mark" <mark.langsdorf@amd.com> 14.02.07 00:19 >>>
>> >--- a/linux-2.6-xen-sparse/arch/i386/mm/hypervisor.c	Fri Feb 
>> 09 10:48:41 2007 +0000
>> >+++ b/linux-2.6-xen-sparse/arch/i386/mm/hypervisor.c	Fri Feb 
>> 09 16:32:04 2007 -0600
>> >@@ -252,7 +252,7 @@ static void contiguous_bitmap_clear(
>> > }
>> > 
>> > /* Protected by balloon_lock. */
>> >-#define MAX_CONTIG_ORDER 9 /* 2MB */
>> >+#define MAX_CONTIG_ORDER 16 /* 256MB */
>> > static unsigned long discontig_frames[1<<MAX_CONTIG_ORDER];
>> > static multicall_entry_t cr_mcl[1<<MAX_CONTIG_ORDER];
>> 
>> This seems dangerous to me.
>
>We need at least 64MB of contiguous memory for the aperture.

I think this should then be established by some other means. 256Mb
(and even the minimum of 64Mb that you say you need) is, for
contiguous memory, almost as good as no limit at all. Among other
reservations I have - how do you intend to make sure the hypervisor
even has a chance of fulfilling this big a request?

But I would certainly like to know Keir's opinion here, too.

Jan