Re: Finish removing MPX from arch/x86?

[Jim Mattson]

On Tue, Oct 4, 2022 at 10:45 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>
> We zapped the userspace MPX ABIs and most of its supporting code in here:
>
>         45fc24e89b7c ("x86/mpx: remove MPX from arch/x86")
>
> But, the XSAVE enabling and KVM code were left in place.  This let folks
> at least keep running guests with MPX.
>
> It's been a couple of years and I don't think I've had a single person
> opine about the loss of MPX.  Intel also followed through and there's no
> MPX to be found on newer CPUs like my "Tiger Lake" 11th Gen Intel(R)
> Core(TM) i7-1165G7.
>
> Is it time to zap MPX from arch/x86/kvm/?

Until Google Cloud retires all of our MPX-capable hardware, we will
require MPX support in KVM.

Removing that support would leave VMs with MPX enabled in XCR0 with
nowhere to go.