Re: [Qemu-devel] [PATCH v2] e1000e: Prevent MSI/MSI-X storms

[Jan Kiszka]

On 2018-07-02 05:40, Jason Wang wrote:
> 
> 
> On 2018年06月30日 14:13, Jan Kiszka wrote:
>> On 2018-04-05 19:41, Jan Kiszka wrote:
>>> From: Jan Kiszka <address@hidden>
>>>
>>> Only signal MSI/MSI-X events on rising edges. So far we re-triggered the
>>> interrupt sources even if the guest did no consumed the pending one,
>>> easily causing interrupt storms.
>>>
>>> Issue was observable with Linux 4.16 e1000e driver when MSI-X was used.
>>> Vector 2 was causing interrupt storms after the driver activated the
>>> device.
>>>
>>> Signed-off-by: Jan Kiszka <address@hidden>
>>> ---
>>>
>>> Changes in v2:
>>>   - also update msi_causes_pending after EIAC changes (required because
>>>     there is no e1000e_update_interrupt_state after that
>>>
>>>   hw/net/e1000e_core.c | 11 +++++++++++
>>>   hw/net/e1000e_core.h |  2 ++
>>>   2 files changed, 13 insertions(+)
>>>
>>> diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
>>> index c93c4661ed..d6ddd59986 100644
>>> --- a/hw/net/e1000e_core.c
>>> +++ b/hw/net/e1000e_core.c
>>> @@ -2027,6 +2027,7 @@ e1000e_msix_notify_one(E1000ECore *core,
>>> uint32_t cause, uint32_t int_cfg)
>>>       }
>>>         core->mac[ICR] &= ~effective_eiac;
>>> +    core->msi_causes_pending &= ~effective_eiac;
>>>         if (!(core->mac[CTRL_EXT] & E1000_CTRL_EXT_IAME)) {
>>>           core->mac[IMS] &= ~effective_eiac;
>>> @@ -2123,6 +2124,13 @@ e1000e_send_msi(E1000ECore *core, bool msix)
>>>   {
>>>       uint32_t causes = core->mac[ICR] & core->mac[IMS] &
>>> ~E1000_ICR_ASSERTED;
>>>   +    core->msi_causes_pending &= causes;
>>> +    causes ^= core->msi_causes_pending;
>>> +    if (causes == 0) {
>>> +        return;
>>> +    }
>>> +    core->msi_causes_pending |= causes;
>>> +
>>>       if (msix) {
>>>           e1000e_msix_notify(core, causes);
>>>       } else {
>>> @@ -2160,6 +2168,9 @@ e1000e_update_interrupt_state(E1000ECore *core)
>>>       core->mac[ICS] = core->mac[ICR];
>>>         interrupts_pending = (core->mac[IMS] & core->mac[ICR]) ? true
>>> : false;
>>> +    if (!interrupts_pending) {
>>> +        core->msi_causes_pending = 0;
>>> +    }
>>>         trace_e1000e_irq_pending_interrupts(core->mac[ICR] &
>>> core->mac[IMS],
>>>                                           core->mac[ICR],
>>> core->mac[IMS]);
>>> diff --git a/hw/net/e1000e_core.h b/hw/net/e1000e_core.h
>>> index 7d8ff41890..63a15510cc 100644
>>> --- a/hw/net/e1000e_core.h
>>> +++ b/hw/net/e1000e_core.h
>>> @@ -109,6 +109,8 @@ struct E1000Core {
>>>       NICState *owner_nic;
>>>       PCIDevice *owner;
>>>       void (*owner_start_recv)(PCIDevice *d);
>>> +
>>> +    uint32_t msi_causes_pending;
>>>   };
>>>     void
>>>
>> Ping again, this one is still open.
>>
>> Jan
> 
> Sorry for the late.
> 
> Just one thing to confirm, I think the reason that we don't need to
> migrate msi_cause_pending is that it can only lead at most one more
> signal of MSI on destination?

Right, a cleared msi_causes_pending on the destination may lead to one
spurious interrupt injects per vector. That should be tolerable.

Jan

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