Re: [PATCH 25/35] x86/cet/shstk: Add user-mode shadow stack support

Dave Hansen
2022-02-12T00:11:10Z

On 2/11/22 16:07, Andy Lutomirski wrote:
> On Fri, Feb 11, 2022, at 3:37 PM, 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.
> PASID? PASID is all kinds of weird. I assume you mean switching it
> with all the normal state.

I was grouping PASID along with the CET MSRs because they're the only
supervisor state. But, yeah, it's all XRSTOR'd at the same spot right
now, user or kernel.