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SubjectRe: [PATCH] cpu/hw_random cleanups
Jeff Garzik wrote:
> Here are the requested cleanups to cpu capabilities and hw_random.c.
>
> For x86 experts, the new cpu cap words are what needs looking over.
> For example, I wonder if storing Intel's cpuid(0x00000001) ecx
> register output is wise on older Intel cpus. I worry about garbage
> appearing there. Is that a false worry?
>

Yes; it should be completely safe.

> This has only been tested on Via Nehemiah CPUs... I have a laptop with
> an Intel RNG on it at home, and will be testing with that later on
> tonight to make sure nothing is broken. I'm hoping Alan or somebody can
> test AMD RNG... if not I'll poke around work and see if there are any
> boxes I can test on.
>
> WRT hw_random, the main change there is to allow multiple independent
> openers to read(2) simultaneously, by removing the semaphore that
> limited userspace to a single open(2)er.
>
> Comments welcome. This patch is to be considered as a fourth patch in
> the previously-posted hw_random series.
>
>
> ===== arch/i386/kernel/cpu/centaur.c 1.7 vs edited =====
> --- 1.7/arch/i386/kernel/cpu/centaur.c Tue Mar 11 21:35:40 2003
> +++ edited/arch/i386/kernel/cpu/centaur.c Thu Mar 13 13:31:08 2003
> @@ -256,9 +256,10 @@
> if (cpuid_eax(0xC0000000) >= 0xC0000001) {
> set_bit(X86_FEATURE_CENTAUR_EFF, c->x86_capability);
>

There is also no need to set a special feature bit for the existence of
the feature flags. If they are not present the additional capability
word will simply be zero.


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