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e1000e: Fix possible interrupt loss when using MSI

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Commit "e1000e: Prevent MSI/MSI-X storms" introduced msi_causes_pending
to prevent interrupt storms problem. It was tested with MSI-X.

In case of MSI, the guest can rely solely on interrupts to clear ICR.
Upon clearing all pending interrupts, msi_causes_pending gets cleared.
However, when e1000e_itr_should_postpone() in e1000e_send_msi() returns
true, MSI never gets fired by e1000e_intrmgr_on_throttling_timer()
because msi_causes_pending is still set. This results in interrupt loss.

To prevent this, we need to clear msi_causes_pending when MSI is going
to get fired by the throttling timer. The guest can then receive
interrupts eventually.

Signed-off-by: Ake Koomsin <ake@igel.co.jp>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Ake Koomsin 2022-07-20 20:13:03 +09:00 committed by Jason Wang
parent 5288bee45f
commit dd0ef12866
1 changed files with 2 additions and 0 deletions
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2
hw/net/e1000e_core.c
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@ -159,6 +159,8 @@ e1000e_intrmgr_on_throttling_timer(void *opaque)
if (msi_enabled(timer->core->owner)) {
trace_e1000e_irq_msi_notify_postponed();
/* Clear msi_causes_pending to fire MSI eventually */
timer->core->msi_causes_pending = 0;
e1000e_set_interrupt_cause(timer->core, 0);
} else {
trace_e1000e_irq_legacy_notify_postponed();