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Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and
From: |
Vincent Bernat |
Subject: |
Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge |
Date: |
Tue, 09 Jan 2018 08:04:26 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) |
❦ 8 janvier 2018 21:19 -0200, Eduardo Habkost <address@hidden> :
>> > 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/address@hidden/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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