[MODERATED] Re: GPZv4

[Jon Masters <jcm@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1422 bytes --]

On 04/17/2018 03:31 PM, speck for Borislav Petkov wrote:
> On Tue, Apr 17, 2018 at 02:26:58PM -0400, speck for Jon Masters wrote:
>> * AMD - They have chicken bits that can disable SSB. They won't provide
>> these except on the condition that we agree not to disable by default.
>> Therefore, I have the magic bit info but can't share it quite yet. It
> 
> Oh, we know the bits.
> 
>> involves writing into two uarch specific MSRs and won't be SPEC_CTRL. I
>> can assist coordinating whatever is agreed here getting back to AMD.
> 
> There's nothing to coordinate - the default setting should be off on
> AMD, that's it.

Let's make sure we're talking about the right thing when we talk about
things being on or off. I usually always talk about a performance
feature being on or off, not a mitigation. Therefore, I read the above
as "MD is off by default", meaning the performance feature is disabled.

This is our current thinking. However, AMD disagree with this and prefer
to leave the feature enabled by default. That would mean having to (at a
minimum) address all of the userspace exposure with prctl(), seccomp(),
or other interfaces, and get that all done within the next month. For
the actual browsers, sure, there will be process isolation updates.

So can you clarify what you meant by "off on AMD" by default?

Jon.

-- 
Computer Architect | Sent from my Fedora powered laptop