Re: Arch qualification for buster: call for DSA, Security, toolchain concerns
- To: Geert Uytterhoeven <geert@linux-m68k.org>
- Cc: lkcl@lkcl.net, debian-release@lists.debian.org, debian-riscv@lists.debian.org, debian-admin@lists.debian.org, team@security.debian.org, Debian GCC Maintainers <debian-gcc@lists.debian.org>, debian-glibc@lists.debian.org, debian-arm@lists.debian.org
- Subject: Re: Arch qualification for buster: call for DSA, Security, toolchain concerns
- From: lsorense@csclub.uwaterloo.ca (Lennart Sorensen)
- Date: Fri, 29 Jun 2018 15:00:29 -0400
- Message-id: <[🔎] 20180629190029.oneyxtud646ujub2@csclub.uwaterloo.ca>
- In-reply-to: <[🔎] CAMuHMdWtYPMm6dYofjQJZUpKXYmwo=NFMqKYXZJ-v+7SWymG3Q@mail.gmail.com>
- References: <[🔎] d47ea159-ace7-e36d-ccb7-14ea911dbc6e@thykier.net> <[🔎] CAPweEDyMk+W5BEQ5JCLDQ5xBcwAyzojY56W1nkvqn2eaeM_2sA@mail.gmail.com> <[🔎] 20180629144810.dxbauqnmg74mdesv@csclub.uwaterloo.ca> <[🔎] CAMuHMdWtYPMm6dYofjQJZUpKXYmwo=NFMqKYXZJ-v+7SWymG3Q@mail.gmail.com>
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
branch prediction.
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.
--
Len Sorensen
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