svn commit: r327876 - in head/sys/arm64: arm64 include

[Andrew Turner]

> On 12 Jan 2018, at 14:10, Marcin Wojtas <mw at semihalf.com> wrote:
> 
> Hi Andrew,
> 
> 
> 
> 2018-01-12 15:01 GMT+01:00 Andrew Turner <andrew at freebsd.org <mailto:andrew at freebsd.org>>:
>> Author: andrew
>> Date: Fri Jan 12 14:01:38 2018
>> New Revision: 327876
>> URL: https://svnweb.freebsd.org/changeset/base/327876
>> 
>> Log:
>>  Workaround Spectre Variant 2 on arm64.
>> 
>>  We need to handle two cases:
>> 
>>  1. One process attacking another process.
>>  2. A process attacking the kernel.
>> 
>>  For the first case we clear the branch predictor state on context switch
>>  between different processes. For the second we do this when taking an
>>  instruction abort on a non-userspace address.
>> 
>>  To clear the branch predictor state a per-CPU function pointer has been
>>  added. This is set by the new cpu errata code based on if the CPU is
>>  known to be affected.
>> 
>>  On Cortex-A57, A72, A73, and A75 we call into the PSCI firmware as newer
>>  versions of this will clear the branch predictor state for us.
>> 
>>  It has been reported the ThunderX is unaffected, however the ThunderX2 is
>>  vulnerable. The Qualcomm Falkor core is also affected. As FreeBSD doesn't
>>  yet run on the ThunderX2 or Falkor no workaround is included for these CPUs.
> 
> Regardless ThunderX2 / Falkor work-arounds, do I understand correctly
> that pure CA72 machines, such as Marvell Armada 7k/8k are immune to
> Variant 2 now?

It is my understanding that the A72 will be immune with this patch and an updated Arm Trusted Firmware as documented in [1].

Andrew

[1] https://github.com/ARM-software/arm-trusted-firmware/wiki/ARM-Trusted-Firmware-Security-Advisory-TFV-6 <https://github.com/ARM-software/arm-trusted-firmware/wiki/ARM-Trusted-Firmware-Security-Advisory-TFV-6>