[PATCH v2 00/12] x86: tag application address space for devices

[Fenghua Yu]

Hi, Peter,
On Mon, Jun 15, 2020 at 09:52:02AM +0200, Peter Zijlstra wrote:
> On Fri, Jun 12, 2020 at 05:41:21PM -0700, Fenghua Yu wrote:
> 
> > This series only provides simple and basic support for ENQCMD and the MSR:
> > 1. Clean up type definitions (patch 1-3). These patches can be in a
> >    separate series.
> >    - Define "pasid" as "unsigned int" consistently (patch 1 and 2).
> >    - Define "flags" as "unsigned int"
> > 2. Explain different various technical terms used in the series (patch 4).
> > 3. Enumerate support for ENQCMD in the processor (patch 5).
> > 4. Handle FPU PASID state and the MSR during context switch (patches 6-7).
> > 5. Define "pasid" in mm_struct (patch 8).
> > 5. Clear PASID state for new mm and forked and cloned thread (patch 9-10).
> > 6. Allocate and free PASID for a process (patch 11).
> > 7. Fix up the PASID MSR in #GP handler when one thread in a process
> >    executes ENQCMD for the first time (patches 12).
> 
> If this is per mm, should not switch_mm() update the MSR ? I'm not
> seeing that, nor do I see it explained why not.

PASID value is per mm and all threads in a process have the same PASID
value in the MSR. However, the MSR is per thread and is context switched
by XSAVES/XRSTROS in patches 6-7.

Thanks.

-Fenghua