Re: [RFC] x86: xsave/xrstor support, ucontext_t extensions

From: Suresh Siddha
Date: Fri May 23 2008 - 14:09:49 EST

On Thu, May 22, 2008 at 07:49:18PM -0700, H. Peter Anvin wrote:
> Roland McGrath wrote:
> >>hmm.. so the kernel needs to export all the cpuid info (that the kernel
> >>enables and supports) to the user through some mechanism then?
> >
> >For a cheap interface, we use AT_HWCAP for this. Unfortunately that only
> >covers the first 32 bits of CPUID info. (For another cheap interface,
> >giving all the CPUID bits in the vDSO would be easy.)
> >
> >For a clunky interface that already exists and is "simple" to use,
> >there is /dev/cpu/0/cpuid now. I wonder if having a device node and
> >opening it too much for applications that consider the vDSO too complex.
> I doubt it.

Ok. If really needed, they can use this interface aswell. But I don't
see a need for a new system call / other mechanism, just for xsave
purpose. They can rely on cpuid or any other equivalent infrastructure the
kernel provides.

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