Re: [PATCH 00/29] x86: Kernel IBT

[Andrew Cooper]

On 19/02/2022 09:58, Peter Zijlstra wrote:
> On Sat, Feb 19, 2022 at 01:29:45AM +0000, Edgecombe, Rick P wrote:
>> On Fri, 2022-02-18 at 17:49 +0100, Peter Zijlstra wrote:
>>> This is an (almost!) complete Kernel IBT implementation. It's been
>>> self-hosting
>>> for a few days now. That is, it runs on IBT enabled hardware
>>> (Tigerlake) and is
>>> capable of building the next kernel.
>>>
>>> It is also almost clean on allmodconfig using GCC-11.2.
>>>
>>> The biggest TODO item at this point is Clang, I've not yet looked at
>>> that.
>> Do you need to turn this off before kexec?
> Probably... :-) I've never looked at that code though; so I'm not
> exactly sure where to put things.
>
> I'm assuming kexec does a hot-unplug of all but the boot-cpu which then
> leaves only a single CPU with state in machine_kexec() ? Does the below
> look reasonable?

If you skip writing to S_CET on hardware that doesn't have it, probably.

~Andrew