Re: [Qemu-devel] [PATCH 1/1] i386: Add PKU/OSPKE on Skylake-Server CPU model

[Eduardo Habkost]

On Wed, Oct 17, 2018 at 12:48:58PM +0200, Paolo Bonzini wrote:
> On 17/10/2018 11:30, Tao Xu wrote:
> > As the release document ref below link (page 13):
> > https://software.intel.com/sites/default/files/managed/c5/15/\
> > architecture-instruction-set-extensions-programming-reference.pdf
> > 
> > PKU is supported in Skylake Server (Only Server) and later, and 
> > on Intel(R) Xeon(R) Processor Scalable Family. OSPKE is to reads 
> > the value of PKRU (Instruction of PKU) into EAX and clears EDX.
> > So PKU/OSPKE are supposed to be in Skylake-Server CPU model. 
> > And PKU/OSPKE 's CPUID has been exposed to QEMU. But PKU/OSPKE
> > can't be find in Skylake-Server CPU model in the code. 
> > So this patch will fix PKU/OSPKE this issue in Skylake-Server 
> > CPU model.  
> 
> OSPKE is not needed, since it is added automatically based on CR4 (and
> is not set on boot).

Correct.

> 
> Also, the guru of CPU model compatibility is Eduardo, so I'll wait for
> him to chime in anyway.

Sorry for taking so long to reply.  This can be safely done only
if every host that is able to run Skylake-Server today is
guaranteed to support PKU.  Is that the case?

You'll also need Skylake-Server-*-cpu.pku=off entries on
PC_COMPAT_3_0 to keep PKU disabled on pc-*-3.0 and older.

-- 
Eduardo