Re: [PATCH v3 44/59] KVM: arm/arm64: GICv4: Handle MOVI applied to a VLPI

Marc Zyngier
2017-08-30T14:08:01Z

On 28/08/17 19:18, Christoffer Dall wrote:
> On Mon, Jul 31, 2017 at 06:26:22PM +0100, Marc Zyngier wrote:
>> When the guest issues a MOVI, we need to tell the physical ITS
>> that we're now targetting a new vcpu. This is done by extracting
>> the current mapping, updating the target, and reapplying the
>> mapping. The core ITS code should do the right thing.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>> virt/kvm/arm/vgic/vgic-its.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index 79bac93d3e7d..aaad577ce328 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -706,6 +706,19 @@ static int vgic_its_cmd_handle_movi(struct kvm *kvm, struct vgic_its *its,
>> ite->irq->target_vcpu = vcpu;
>> spin_unlock(&ite->irq->irq_lock);
>>
>> + if (ite->irq->hw) {
>> + struct its_vlpi_map map;
>> + int ret;
>> +
>> + ret = its_get_vlpi(ite->irq->host_irq, &map);
>> + if (ret)
>> + return ret;
>> +
>> + map.vpe_idx = vcpu->vcpu_id;
>> +
>> + return its_map_vlpi(ite->irq->host_irq, &map);
>
> Since you're not holding the irq_lock across these two calls, would it
> be possible that the forwarding was removed through some other call path
> here, and could you end up passing an invalid host_irq to its_map_vlpi?
I believe we should be OK here, as we hold the ITS mutex during any
command processing, and both the forward/unforward paths take that same
mutex.

On a slightly different note, it looks like the MOVI code could benefit
from using vgic_its_resolve_lpi(), which has been introduce earlier in
this series.

Thanks,

M.
--
Jazz is not dead. It just smells funny...