Re: [PATCH v1 4/4] KVM: arm64: Initialize trap register values in hyp in pKVM

[Oliver Upton <oliver.upton@linux.dev>]

On Tue, Oct 15, 2024 at 09:19:03AM +0100, Fuad Tabba wrote:
> Hi Oliver,
> 
> On Tue, 15 Oct 2024 at 08:57, Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > On Mon, Oct 14, 2024 at 11:24:12AM +0100, Fuad Tabba wrote:
> > > Handle the initialization of trap registers at the hypervisor in
> > > pKVM, even for non-protected guests. The host is not trusted with
> > > the values of the trap registers, regardless of the VM type.
> > > Therefore, when switching between the host and the guests, only
> > > flush the required bits of the trap registers from the host's
> > > view that are required for hyp-host communication.
> >
> > It'd be a bit more precise to just mention that the host is allowed to
> > configure TWI and TWE still for opportunistic scheduling, as neither
> > affects the protection of VMs or the hypervisor.
> 
> Sure, will do.
> 
> >
> > >       pvm_init_trap_regs(vcpu);
> > >       pvm_init_traps_aa64pfr0(vcpu);
> > >       pvm_init_traps_aa64pfr1(vcpu);
> >
> > aside: it'd be great to reorganize all of these traps in terms of the
> > affected trap register and not the feature register.
> >
> > But that can happen later.
> 
> I do have patches for that, but I thought I'll start with these first
> since they pave the way to those.

Entirely reasonable, as you're fixing a legitimate issue here.

-- 
Thanks,
Oliver