Re: [PATCH 00/31 v2] PTI support for x86_32

[Andrew Cooper]

On 09/02/2018 21:09, Pavel Machek wrote:
> On Fri 2018-02-09 17:47:43, Andy Lutomirski wrote:
>> PCID bit set in CPUID should print a big fat warning like "WARNING:
>> you are using 32-bit PTI on a 64-bit PCID-capable CPU.  Your
>> performance will increase dramatically if you switch to a 64-bit
>> kernel."
> Hardware supports PCID even on 32-bit kernels, no?

Attempting to set CR4.PCIDE is disallowed outside of long mode.  It is
strictly a 64bit-only feature.

~Andrew