Re: [PATCH 3/3] x86/msr: Add an MSR write callback

[Peter Zijlstra]

On Wed, Jun 10, 2020 at 01:00:37PM +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@xxxxxxx>
> 
> Add a callback which gets executed after a MSR is written from
> userspace. This is needed because in the case of AMD's MSR_AMD64_LS_CFG
> MSR which gets cached in the kernel, the cached value needs to be
> updated after the write, otherwise latter doesn't stick.

We cache a whole bunch of MSRs in kernel. Why is this one special?

If you write using the stupid msr device, you get to keep all pieces.