Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge

[Vincent Bernat <vincent@bernat.im>]

 ❦  8 janvier 2018 21:19 -0200, Eduardo Habkost <ehabkost@redhat.com> :

>> > GET_SUPPORTED_CPUID seems to still return PCID as supported
>> > without EPT, doesn't it?
>> 
>> Indeed it is!  It will also be useful for KPTI performance without
>> INVPCID, but it won't be useful without EPT.
>
> Well, I can live with "not useful without EPT", as long as it
> doesn't mean "broken without EPT".  It looks like we can safely
> enable it, as long as:
>
> 2) we confirm if all Intel Westmere/SandyBridge/IvyBridge CPUs
>    have PCID;

I didn't find an authoritative information about that on Intel
website. Various sites indeed says the feature was introduced in
Westmere. And Greg KH mentions Westmere here too:
 https://mail-archive.com/linux-kernel@vger.kernel.org/msg1576774.html

> 1) QEMU documentation states that it requires Linux v3.6 or newer
>    for KVM.

I have updated the patch and sent it in a new thread. It's now based on
x86-next.
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