[PATCH v3 1/7] KVM: arm64: Discard any SVE state when entering KVM guests

[Marc Zyngier]

On Tue, 20 Sep 2022 21:21:33 +0100,
Mark Brown <broonie at kernel.org> wrote:
> 
> [1  <text/plain; us-ascii (quoted-printable)>]
> On Tue, Sep 20, 2022 at 05:44:01PM +0100, Marc Zyngier wrote:
> > Mark Brown <broonie at kernel.org> wrote:
> 
> > >  void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
> > >  {
> > >  	BUG_ON(!current->mm);
> > > -	BUG_ON(test_thread_flag(TIF_SVE));
> > > +
> > > +	fpsimd_kvm_prepare();
> > 
> > Why is this *before* the check against system_supports_fpsimd()? I
> > don't think the architecture allows SVE without FP, for obvious
> > reasons...
> 
> Good point, though now that I think about it I can't think of a
> requirement for FP when implementing SME (there's certainly not
> one for SVE).

Even if the architecture was allowing this madness, KVM doesn't allow
SVE if FP is not available, just like the rest of the kernel.

> There's no use for that hook now though.

Care to clarify?

	M.

-- 
Without deviation from the norm, progress is not possible.