Re: [PATCH] hw/arm/virt: KVM: Enable PAuth when supported by the host

[Andrew Jones]

On Mon, Jan 03, 2022 at 06:05:41PM +0000, Marc Zyngier wrote:
> Andrew Jones <drjones@redhat.com> wrote:
> > 
> > Thanks for considering a documentation update. In this case, though, I
> > think we should delete the "TCG VCPU Features" pauth paragraph, rather
> > than add a new "KVM VCPU Features" pauth paragraph. We don't need to
> > document each CPU feature. We just document complex ones, like sve*,
> > KVM specific ones (kvm-*), and TCG specific ones (now only pauth-impdef).
> 
> Sure, works for me. Do we need to keep a trace of the available
> options?

For arm we need to extend target/arm/helper.c:arm_cpu_list() to output
the possible flags like x86 does. On x86 doing this

  qemu-system-x86_64 -cpu help

not only gives us a list of cpu types, but also a list of flags we can
provide to the cpus (although not all flags will work on all cpus...)
On arm doing this

  qemu-system-aarch64 -cpu help

only gives us a list of cpu types.


> I'm not sure how a user is supposed to find out about those
> (I always end-up grepping through the code base, and something tells
> me I'm doing it wrong...). The QMP stuff flies way over my head.
>

Indeed, currently grepping is less awkward than probing with QMP.
With an extension to target/arm/helper.c:arm_cpu_list() we can
avoid grepping too. I've just added this to my TODO [again]. It
was there once already, but fell off the bottom...

Thanks,
drew