Re: IO space memcpy support for userspace.

From: Dave Airlie
Date: Sat Dec 06 2008 - 01:30:34 EST

On Sat, Dec 6, 2008 at 6:27 AM, Roland McGrath <roland@xxxxxxxxxx> wrote:
> There is never going to be something in memcpy that makes any magical
> kernel calls to find out about an address. That's just loony, sorry.
> memcpy is inlined away by the compiler in good cases. It's like you'd
> asked for "*ptr" to have magical constraints by the compiler generating
> code to ask the kernel if "ptr" is a special address. Uh, really?

Yeah I didn't think it was a good idea, its what HPUX does, so that
implied it probably wasn't a good idea.

I was just hoping it might help people come up with a good idea.


> If you can think of an efficient way to determine it and do what you need,
> then you could write optimized routines that do that in the vDSO perhaps.
> Thanks,
> Roland
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