Re: [PATCH 3/4] arm64: KVM: let other tasks run when hitting WFE

Will Deacon
2013-07-19T14:26:07Z

On Fri, Jul 19, 2013 at 02:53:54PM +0100, Marc Zyngier wrote:
> So far, when a guest executes WFE (like when waiting for a spinlock
> to become unlocked), we don't do a thing and let it run uninterrupted.
>
> Another option is to trap a blocking WFE and offer the opportunity
> to the scheduler to switch to another task, potentially giving the
> vcpu holding the spinlock a chance to run sooner.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

[...]

> +static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> - kvm_vcpu_block(vcpu);
> + if (kvm_vcpu_get_hsr(vcpu) & 1)
> + cond_resched();

The hardcoded `1' doesn't make it obvious that we're treating wfi and wfe
differently. Could you use a #define for that bit in hsr.iss please?

Will