Re: [RFC PATCH 06/16] target/arm/kvm-rme: Initialize vCPU

[Jean-Philippe Brucker]

On Fri, Jan 27, 2023 at 12:37:12PM -1000, Richard Henderson wrote:
> On 1/27/23 05:07, Jean-Philippe Brucker wrote:
> > +static int kvm_arm_rme_get_core_regs(CPUState *cs)
> > +{
> > +    int i, ret;
> > +    struct kvm_one_reg reg;
> > +    ARMCPU *cpu = ARM_CPU(cs);
> > +    CPUARMState *env = &cpu->env;
> > +
> > +    for (i = 0; i < 8; i++) {
> > +        reg.id = AARCH64_CORE_REG(regs.regs[i]);
> > +        reg.addr = (uintptr_t) &env->xregs[i];
> > +        ret = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
> > +        if (ret) {
> > +            return ret;
> > +        }
> > +    }
> > +
> > +    return 0;
> > +}
> 
> Wow, this is quite the restriction.
> 
> I get that this is just enough to seed the guest for boot, and take SMC
> traps, but I'm concerned that we can't do much with the machine underneath,
> when it comes to other things like "info registers" or gdbstub will be
> silently unusable.  I would prefer if we can somehow make this loudly
> unusable.

For "info registers", which currently displays zero values for all regs,
we can instead return an error message in aarch64_cpu_dump_state().

For gdbstub, I suspect we should disable it entirely since it seems
fundamentally incompatible with confidential VMs, but I need to spend more
time on this.

Thanks,
Jean