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Date: Sun, 16 Mar 2008 16:52:42 +0100
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-core] pgprot_noncached for io-remapping?
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Philippe Gerum wrote:
> Jan Kiszka wrote:
>> Hi,
>>
>> doesn't this patch [1] have some relevance for us as well? As we use
>> xnarch_remap_io_page_range also for non-IO memory, I'm hesitating to
>> suggest that we apply this unconditionally at xnarch level. Ideas welc=
ome.
>>
>=20
> Yes, I think it makes a lot of sense on powerpc at least, since doing s=
o will
> set the PAGE_GUARDED bit as well, and we obviously want to avoid any
> out-of-order access of I/O memory.
>=20
> (I don't see the reason to force the VM_RESERVED and VM_IO on the vma t=
hough,
> since remap_pfn_range will do it anyway.)

No, I was talking about cases where we may pass kmalloc'ed memory to
xnarch_remap_io_page_range. In that case, caching and out-of-order
access may be desired for performance reasons.

Jan


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