Re: [PATCH v3 2/3] intel_idle: Sync up the SPEC_CTRL MSR value to x86_spec_ctrl_current

[Waiman Long]

On 6/22/23 05:40, Peter Zijlstra wrote:
> On Wed, Jun 21, 2023 at 10:46:33PM -0700, Josh Poimboeuf wrote:
> > On Wed, Jun 21, 2023 at 08:36:02PM -0400, Waiman Long wrote:
> > > When intel_idle_ibrs() is called, it modifies the SPEC_CTRL MSR to
> > > 0 in order disable IBRS. However, the new MSR value isn't reflected
> > > in x86_spec_ctrl_current which is at odd with the other code that
> > > keep track of its state in that percpu variable. Fix that by updating
> > > x86_spec_ctrl_current percpu value to always match the content of the
> > > SPEC_CTRL MSR.
> > Is this fixing an actual bug or is there some other reason for doing
> > this?
> No actual bug, he did this for his debugfs file -- which is no longer
> part of the series. With that on, you can observe the
> x86_spec_ctrl_current value while idle.

Right. That is the main reason as I want the SPEC_CTRL MSRs value to be 
observable by some external mean:-)

Regards,
Longman