Re: [RFC PATCH v3 1/2] x86: cpu/bugs: add AMD ERAPS support; hardware flushes RSB

[Sean Christopherson]

On Mon, Dec 02, 2024, Dave Hansen wrote:
> On 12/2/24 10:09, Amit Shah wrote:
> > I can still include the summary of the discussion in this patch - I
> > just feel it isn't necessary with the rework.
> 
> It's necessary.
> 
> There's a new hardware feature. You want it to replace a software
> sequence in certain situations. You have to make an actual, coherent
> argument argument as to why the hardware feature is a suitable replacement.
> 
> For instance (and I'm pretty sure we've gone over this more than once),
> the changelog here still makes the claim that a "context switch" and a
> "mov-to-CR3" are the same thing.

+1000.  I want a crisp, precise description of the actual hardware behavior, so
that KVM can do the right thing when virtualizing ERAPS.