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

[Jason Wang <jasowang@redhat.com>]

On 2018年06月30日 14:13, Jan Kiszka wrote:
> On 2018-04-05 19:41, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> 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 <jan.kiszka@siemens.com>
>> ---
>>
>> 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?

Thanks