RE: [Xen-ia64-devel] Re: [PATCH]: ptc.ga for SMP-g

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

Let's make some clarification here:

For IA64 linux, KERNEL_START records start of kernel image which is in 
region 5 for 2.6 kernel while in region 7 for 2.4 kernel. PAGE_OFFSET is 
start of region 7 which never changes with kernel versions.

First [KERNEL_START, KERNEL_START + KERNEL_TR_PAGE_SIZE - 
1] is definitely covered by TR.

The IA64_GRANULE_SIZE (16M/64M) area covering current kernel stack 
is also mapped by TR. Except for init_task, all kernel stacks are 
dynamically allocated from identity mapping area. So if stack of current 
running task happens to reside within [PAGE_OFFSET, PAGE_OFFSET 
+ IA64_GRANULE_SIZE - 1], then that area is mapped by TR. Then once 
stack of next task is outside of that range, TR will be purged and 
re-inserted upon new area.

So I think Isaku is only taking [PAGE_OFFSET, PAGE_OFFSET+64M] as 
an example to explain the issue, with assumption that area doesn't 
contain current kernel stack. :-)

Thanks,
Kevin
>-----Original Message-----
>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Xu,
>Anthony
>Sent: 2006年3月31日 11:35
>To: Isaku Yamahata
>Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx; Tristan Gingold
>Subject: RE: [Xen-ia64-devel] Re: [PATCH]: ptc.ga for SMP-g
>
>>From: Isaku Yamahata [mailto:yamahata@xxxxxxxxxxxxx]
>>Sent: 2006年3月31日 10:53
>>It's right that Linux/ia64 kernel text and statically allocated data
>>are in [0xa000000100000000, ...].
>>However dynamically allocated pages's virtual address are in
>>the area of [PAGE_OFFSET, ...].
>
>Dynamically allocated page is not mapped by TR.
>
>>That is, values which is returned by __get_free_pages() (and its family)
>>are of PAGE_OFFSET + (some offsets).
>>
>>Please see the definition of __pa() and __va() of Linux/ia64.
>># define __pa(x)                ((x) - PAGE_OFFSET)
>># define __va(x)                ((x) + PAGE_OFFSET)
>>
>>
>>
>>--
>>yamahata
>
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