Re: [PATCH 4/5] tsc: wire up entropy generation function

["H. Peter Anvin" <hpa@zytor.com>]

On 06/13/2011 05:39 PM, Kent Borg wrote:
> I was assuming that drivers, responding to an interrupt from some
> external event, would want to make this call.
> Such as a network driver.

Those already are doing this.

> Two points:
> 
> 1. Why look at the high-order bits?  How are they going to have values
> that cannot be inferred?  If you are looking for entropy, the low-order
> bits is where they're going keep it.  (Think Willie Sutton.)  If looking
> at the low-byte is cheaper, then let's be cheap.  If, however, if
> looking at more bytes *is* as cheap, then there is no harm.  But in any
> case let's keep the code lean enough that it can be called from an
> interrupt service routine.

Consider the case where the TSC is running in steps of 64 and you're
using the low 6 bits.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.