On Wed, May 09, 2018 at 09:50:26AM +0100, Marc Zyngier wrote:
> On 08/05/18 17:44, Dave Martin wrote:
> > This patch adds SVE context saving to the hyp FPSIMD context switch
> > path. This means that it is no longer necessary to save the host
> > SVE state in advance of entering the guest, when in use.
> >
> > In order to avoid adding pointless complexity to the code, VHE is
> > assumed if SVE is in use. VHE is an architectural prerequisite for
> > SVE, so there is no good reason to turn CONFIG_ARM64_VHE off in
> > kernels that support both SVE and KVM.
> >
> > Historically, software models exist that can expose the
> > architecturally invalid configuration of SVE without VHE, so if
> > this situation is detected this patch warns and refuses to create a
> > VM. Doing this check at VM creation time avoids race issues
> > between KVM and SVE initialisation.
>
> I don't think the commit log now reflects the code, since we bail out at
> init time and disable KVM altogether.
Will fix to say that we simply disable KVM completely at kvm_init() time
in this case.
[...]
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
[...]
> > @@ -337,8 +341,22 @@ void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,
> >
> > isb();
> >
> > - if (vcpu->arch.host_fpsimd_state) {
> > - __fpsimd_save_state(vcpu->arch.host_fpsimd_state);
> > + if (host_fpsimd) {
> > + /*
> > + * In the SVE case, VHE is assumed: it is enforced by
> > + * Kconfig and kvm_arch_init_vm().
>
> Nit: this is now kvm_arch_init().
Will fix.
[...]
> Otherwise:
>
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Thanks
---Dave
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