On Fri, 2022-02-11 at 15:37 -0800, Dave Hansen wrote: > On 1/30/22 13:18, Rick Edgecombe wrote: > > 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. > > Either way, it would be nice to have some changelog material to that > effect. The only special shadow stack thing the kernel does is WRUSS, which per the SDM only needs the CR4 bit set to work (unlike WRSS). So I think the lazy restore is ok.
