Re: Arch specific mmap attributes

From: David Miller
Date: Wed Apr 07 2010 - 03:18:54 EST

From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Date: Wed, 7 Apr 2010 16:14:29 +0900 (JST)

>> From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
>> Date: Wed, 7 Apr 2010 15:03:45 +0900 (JST)
>> > I'm not against changing kernel internal. I only disagree mmu
>> > attribute fashion will be become used widely.
>> Desktop already uses similar features via PCI mmap
>> attributes and such, not to mention MSR settings on
>> x86.
> Probably I haven't catch your mention. Why userland process
> need to change PCI mmap attribute by mmap(2)? It seems kernel issue.

It uses PCI specific fd ioctls to change the attributes.

It's the same thing as extending the mmap() attribute space, but in a
device specific way.

I think evice and platform specific mmap() attributes are basically
inevitable, at any level, embedded or desktop or whatever. The
fact that we've hacked around the issue with device specific
interfaces like the PCI device ioctls, is no excuse to not
tackle the issue directly and come up with something usable.

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