Re: [PATCH 4.19 041/361] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

Tim Chen
2018-11-21T18:59:28Z

On 11/21/2018 10:21 AM, Jiri Kosina wrote:
> On Wed, 21 Nov 2018, Tim Chen wrote:
>
>>> Is it reverted in Linus's tree? If not, then anything that comes "later
>>> on" will not apply here, right?
>>>
>>> I see the thread asking about this, but I got really conflicting
>>> messages here, and now it's in all of the latest releases, and no
>>> testing seems to have uncovered issues. Is it just a "slow down"
>>> problem?
>>
>> Greg,
>>
>> It could be a big slow down in excess of 20% for some applications.
>> And cross sibling Spectre v2 attack is quite hard to pull off.
>>
>> So till we have the accompanying patchset that only apply STIBP on processes
>> that really need it instead of universally, it should be withheld from
>> stable.
>
> Agreed; it will be trivially reintroduced with the rest, once it's ready.
> It's being built on top of that patch.
>

Thanks. Appreciate it.

Tim