On 2/26/19 5:17 AM, David Gibson wrote:
> On Fri, Feb 22, 2019 at 02:13:22PM +0100, Cédric Le Goater wrote:
>> Instead of switching off the sources, set their state to PENDING to
>> possibly catch a hotplug event occuring while the VM is stopped. At
>> resume, check the previous state and if an interrupt was queued,
>> generate a trigger.
>
> First, I think it would be better to fold this fix into the patch
> introducing the state change handlers.>
> Second, IIUC this would handle any instance of an irq being triggered
> while the VM is stopped.
yes.
> Hotplug interrupts is one obvious case of that, but I'm not sure its
> the only one.
Do we really need to support device hotplug when the VM is stopped ?
Is that a libvirt requirement ?
> VFIO devices could interrupt while the VM is stopped, I think.
If the guest has configured and mapped the IRQs, I would say yes.
> Maybe even emulated devices
> depending on how their synchronization with the cpu run state works.
The console is one example.
> There might be other cases. Does that sound right to you?
yes.
Supporting interrupts while a VM is stopped seems like a weird
test scenario to me. Should we or should we not ?
Thanks,
C.
>> Signed-off-by: Cédric Le Goater <c...@kaod.org>
>> ---
>> hw/intc/spapr_xive_kvm.c | 22 +++++++++++++++++++---
>> 1 file changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
>> index 99a829fb3f60..64d160babb26 100644
>> --- a/hw/intc/spapr_xive_kvm.c
>> +++ b/hw/intc/spapr_xive_kvm.c
>> @@ -500,8 +500,16 @@ static void kvmppc_xive_change_state_handler(void
>> *opaque, int running,
>> if (running) {
>> for (i = 0; i < xsrc->nr_irqs; i++) {
>> uint8_t pq = xive_source_esb_get(xsrc, i);
>> - if (xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_00 + (pq << 8)) !=
>> 0x1) {
>> - error_report("XIVE: IRQ %d has an invalid state", i);
>> + uint8_t old_pq;
>> +
>> + old_pq = xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_00 + (pq << 8));
>> +
>> + /*
>> + * If an interrupt was queued (hotplug event) while VM was
>> + * stopped, generate a trigger.
>> + */
>> + if (pq == XIVE_ESB_RESET && old_pq == XIVE_ESB_QUEUED) {
>> + xive_esb_trigger(xsrc, i);
>> }
>> }
>>
>> @@ -515,7 +523,15 @@ static void kvmppc_xive_change_state_handler(void
>> *opaque, int running,
>> * migration is in progress.
>> */
>> for (i = 0; i < xsrc->nr_irqs; i++) {
>> - uint8_t pq = xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_01);
>> + uint8_t pq = xive_esb_read(xsrc, i, XIVE_ESB_GET);
>> +
>> + /*
>> + * PQ is set to PENDING to possibly catch a hotplug event
>> + * occuring while the VM is stopped.
>> + */
>> + if (pq != XIVE_ESB_OFF) {
>> + pq = xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_10);
>> + }
>> xive_source_esb_set(xsrc, i, pq);
>> }
>>
>
