Re: [Xen-devel] [PATCH 31/57] ARM: new VGIC: Add IRQ sync/flush framework

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/05/2018 04:03 PM, Andre Przywara wrote:
> Implement the framework for syncing IRQs between our emulation and the
> list registers, which represent the guest's view of IRQs.
> This is done in kvm_vgic_flush_hwstate and kvm_vgic_sync_hwstate, which
You probably want to update the names here.

> gets called on guest entry and exit.
> The code talking to the actual GICv2/v3 hardware is added in the
> following patches.
>
> This is based on Linux commit 0919e84c0fc1, written by Marc Zyngier.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
[...]

> +/**
> + * vgic_sync_from_lrs() - Update VGIC state from hardware after a guest's run.
> + * @vcpu: the VCPU for which to transfer from the LRs to the IRQ list.
> + *
> + * Sync back the hardware VGIC state after the guest has run, into our
> + * VGIC emulation structures, It reads the LRs and updates the respective
> + * struct vgic_irq, taking level/edge into account.
> + * This is the high level function which takes care of the conditions,
> + * also bails out early if there were no interrupts queued.
> + * Was: kvm_vgic_sync_hwstate()
> + */
> +void vgic_sync_from_lrs(struct vcpu *vcpu)
> +{
> +    /* An empty ap_list_head implies used_lrs == 0 */
> +    if ( list_empty(&vcpu->arch.vgic.ap_list_head) )
> +        return;
> +
> +    vgic_fold_lr_state(vcpu);
OOI, why did you drop the "if (vgic_cpu->used_lrs)" here? It looks like 
to me you want to avoid calling that function when no LRs are been used.
> +
> +    vgic_prune_ap_list(vcpu);
> +}
Cheers,

--
Julien Grall

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