Re: Arch qualification for buster: call for DSA, Security, toolchain concerns
- To: Geert Uytterhoeven <firstname.lastname@example.org>
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- Subject: Re: Arch qualification for buster: call for DSA, Security, toolchain concerns
- From: email@example.com (Lennart Sorensen)
- Date: Fri, 29 Jun 2018 15:00:29 -0400
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On Fri, Jun 29, 2018 at 06:29:48PM +0200, Geert Uytterhoeven wrote:
> Are you sure you're not interchanging A8 and A9, cfr. Linux kernel commit
> e388b80288aade31 ("ARM: spectre-v2: add Cortex A8 and A15 validation of the
> IBE bit")?
Yes. That is the main reason the A9 is faster than the A8 at the same
clock speed by quite a bit.
For example http://www.360doc.com/content/12/0806/14/350555_228637047.shtml says:
Cortex-A9 has many advanced features for a RISC CPU, such as speculative
data accesses, branch prediction, multi-issuing of instructions,
hardware cache coherency, out-of-order execution and register renaming.
Cortex-A8 does not have these, except for dual-issuing instructions and
So the A8 still has branch prediction so it can keep the pipeline fed,
even with in order execution. Spectre isn't really about out-of-order
excution as much as it is about speculative memory accesses which some
in-order execution chips have too.