Re: [PATCH v4 3/9] KVM: Clear assigned guest IRQ on release

[Avi Kivity <avi@redhat.com>]

On 11/08/2010 01:21 PM, Jan Kiszka wrote:
> When we deassign a guest IRQ, clear the potentially asserted guest line.
> There might be no chance for the guest to do this, specifically if we
> switch from INTx to MSI mode.
>
> Signed-off-by: Jan Kiszka<jan.kiszka@siemens.com>
> ---
>   virt/kvm/assigned-dev.c |    3 +++
>   1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
> index 7c98928..ecc4419 100644
> --- a/virt/kvm/assigned-dev.c
> +++ b/virt/kvm/assigned-dev.c
> @@ -141,6 +141,9 @@ static void deassign_guest_irq(struct kvm *kvm,
>   	kvm_unregister_irq_ack_notifier(kvm,&assigned_dev->ack_notifier);
>   	assigned_dev->ack_notifier.gsi = -1;
>
> +	kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
> +		    assigned_dev->guest_irq, 0);
> +
>   	if (assigned_dev->irq_source_id != -1)
>   		kvm_free_irq_source_id(kvm, assigned_dev->irq_source_id);
>   	assigned_dev->irq_source_id = -1;

I guess this can't hurt.  Did you see it happen in practice?

Note: all this kvm_set_irq(..., [01]) is incorrect as it doesn't account 
for polarity.  Currently the qemu-emulated chipset uses level high pci 
interrupts, but that's not a given from kvm's point of view.

I think vfio fixes this by only routing msi interrupts via the kernel, 
and routing level interrupts through userspace, which can adjust 
polarity.  Alex/Michael?

-- 
error compiling committee.c: too many arguments to function