Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code

Alexandre Chartre
2020-11-18T07:07:10Z

On 11/17/20 10:23 PM, Borislav Petkov wrote:
> On Tue, Nov 17, 2020 at 08:02:51PM +0100, Alexandre Chartre wrote:
>> No. This prevents the guest VM from gathering data from the host
>> kernel on the same cpu-thread. But there's no mitigation for a guest
>> VM running on a cpu-thread attacking another cpu-thread (which can be
>> running another guest VM or the host kernel) from the same cpu-core.
>> You cannot use flush/clear barriers because the two cpu-threads are
>> running in parallel.
>
> Now there's your justification for why you're doing this. It took a
> while...
>
> The "why" should always be part of the 0th message to provide
> reviewers/maintainers with answers to the question, what this pile of
> patches is all about. Please always add this rationale to your patchset
> in the future.
>

Sorry about that, I will definitively try to do better next time. :-}

Thanks,

alex.