> From: Philip Guenther <guent...@gmail.com>
> Date: Fri, 5 Jan 2018 20:52:20 -0800
> Unless something unexpected happens, we'll be applying the workaround to
> amd64 first and then working out what to do for i386 and arm* (if still
> though to be necessary for arm) after that.
FWIW, Meltdown is a non-issue for OpenBSD/armv7 and OpenBSD/arm64 at
the moment. The only vulnerable ARM core is the Cortex-A75 which
isn't actually on the market yet. And we don't currently support
non-ARM implementations. That said, we are considering separating the
page tables on arm64 since it seems to be relatively easy and unlikely
to have a severe impact on performance.
Some ARM cores are vulnerable to various Spectre attacks. However
since OpenBSD/armv7 flushes the BTB on each context switch already, it
is unliekly that other processes can be attached. We're still
investigating whether more BTB flushes are necessary. Everything with
a Cortex-A7 core should be safe, which is a large fraction of the
hardware supported by OpenBSD/armv7.
For OpenBSD/arm64 the situation is not so great. Flusihing the BTB
there is almost impossible without a firmware update. However,
everything with a Cortex-A53 core should be safe, which covers the
majority of the hardware supported by OpenBSD/amd64.