* Sameeh Jubran (sam...@daynix.com) wrote:
> The bug was caused by the "receive overrun" (bit #6 of the ICR register)
> interrupt
> which would be triggered post migration in a heavy traffic environment. Even
> though the
> "receive overrun" bit (#6) is masked out by the IMS register (refer to the
> log below)
> the driver still receives an interrupt as the "receive overrun" bit (#6)
> causes the
> "Other" - bit #24 of the ICR register - bit to be set as documented below.
> The driver
> handles the interrupt and clears the "Other" bit (#24) but doesn't clear the
> "receive overrun" bit (#6) which leads to an infinite loop. Apparently the
> Windows
> driver expects that the "receive overrun" bit and other ones - documented
> below - to be
> cleared when the "Other" bit (#24) is cleared.
>
> So to sum that up:
> 1. Bit #6 of the ICR register is set by heavy traffic
> 2. As a results of setting bit #6, bit #24 is set
> 3. The driver receives an interrupt for bit 24 (it doesn't receieve an
> interrupt for bit #6 as it is masked out by IMS)
> 4. The driver handles and clears the interrupt of bit #24
> 5. Bit #6 is still set.
> 6. 2 happens all over again
>
> The Interrupt Cause Read - ICR register:
>
> The ICR has the "Other" bit - bit #24 - that is set when one or more of the
> following
> ICR register's bits are set:
>
> LSC - bit #2, RXO - bit #6, MDAC - bit #9, SRPD - bit #16, ACK - bit #17, MNG
> - bit #18
>
> Log sample of the storm:
>
> 27563@1494850819.411877:e1000e_irq_pending_interrupts ICR PENDING: 0x1000000
> (ICR: 0x815000c2, IMS: 0x1a00004)
> 27563@1494850819.411900:e1000e_irq_pending_interrupts ICR PENDING: 0x0 (ICR:
> 0x815000c2, IMS: 0xa00004)
> 27563@1494850819.411915:e1000e_irq_pending_interrupts ICR PENDING: 0x0 (ICR:
> 0x815000c2, IMS: 0xa00004)
> 27563@1494850819.412380:e1000e_irq_pending_interrupts ICR PENDING: 0x0 (ICR:
> 0x815000c2, IMS: 0xa00004)
> 27563@1494850819.412395:e1000e_irq_pending_interrupts ICR PENDING: 0x0 (ICR:
> 0x815000c2, IMS: 0xa00004)
> 27563@1494850819.412436:e1000e_irq_pending_interrupts ICR PENDING: 0x0 (ICR:
> 0x815000c2, IMS: 0xa00004)
> 27563@1494850819.412441:e1000e_irq_pending_interrupts ICR PENDING: 0x0 (ICR:
> 0x815000c2, IMS: 0xa00004)
> 27563@1494850819.412998:e1000e_irq_pending_interrupts ICR PENDING: 0x1000000
> (ICR: 0x815000c2, IMS: 0x1a00004)
>
> This commit solves:
> https://bugzilla.redhat.com/show_bug.cgi?id=1447935
> https://bugzilla.redhat.com/show_bug.cgi?id=1449490
>
> Signed-off-by: Sameeh Jubran <sjub...@redhat.com>
Thanks, I tested this with our downstream and it does
fix the reproducer for 1447935 for me, so:
Tested-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Dave
> ---
> hw/net/e1000e_core.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
> index 28c5be1..8174b53 100644
> --- a/hw/net/e1000e_core.c
> +++ b/hw/net/e1000e_core.c
> @@ -2454,14 +2454,17 @@ e1000e_set_ics(E1000ECore *core, int index, uint32_t
> val)
> static void
> e1000e_set_icr(E1000ECore *core, int index, uint32_t val)
> {
> + uint32_t icr = 0;
> if ((core->mac[ICR] & E1000_ICR_ASSERTED) &&
> (core->mac[CTRL_EXT] & E1000_CTRL_EXT_IAME)) {
> trace_e1000e_irq_icr_process_iame();
> e1000e_clear_ims_bits(core, core->mac[IAM]);
> }
>
> - trace_e1000e_irq_icr_write(val, core->mac[ICR], core->mac[ICR] & ~val);
> - core->mac[ICR] &= ~val;
> + icr = core->mac[ICR] & ~val;
> + icr = (val & E1000_ICR_OTHER) ? (icr & ~E1000_ICR_OTHER_CAUSES) : icr;
> + trace_e1000e_irq_icr_write(val, core->mac[ICR], icr);
> + core->mac[ICR] = icr;
> e1000e_update_interrupt_state(core);
> }
>
> --
> 2.8.1.185.gdc0db2c
>
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
