On Fri, Feb 11, 2022, at 3:37 PM, Dave Hansen wrote:

On 1/30/22 13:18, Rick Edgecombe wrote:

quoted

Add the user shadow stack MSRs to the xsave helpers, so they can be used
to implement the functionality.

Do these MSRs ever affect kernel-mode operation?

If so, we might need to switch them more aggressively at context-switch
time like PKRU.

If not, they can continue to be context-switched with the PASID state
which does not affect kernel-mode operation.

PASID?  PASID is all kinds of weird.  I assume you mean switching it with all the normal state.

Either way, it would be nice to have some changelog material to that effect.