Re: [Qemu-devel] [PATCH 0/2] e1000: Introducing an upper bound of interrupts

[Denis V. Lunev]

On 03/17/2016 10:37 AM, Sameeh Jubran wrote:
> This patch series introduces an upper bound for the number of interrupts
> per second. This feature is supported by the real hardware, however up
> until now it wasn't implemented in e1000. This feature is very
> significant, it can prevent an interrupt storm by giving the driver
> a bounded inter-interrupt interval to handle interrupts.
>
> This patch was made after observing an interrupt storm in Windows 10
> when disabling e1000.
>
> How reproducible:
>
> Steps to reproduce:
> 1. Start Win 10 guest with e1000 device.
> 2. Go to device manager and try to disable and enable the device.
> 3. After several enable/disable to the device the guest hangs when
> the device is being disabled.
>
> Actual results:
> Guest hang after click OK button.
>
> Expected results:
> Device is disabled.
>
> After applying the patch the guest no longer hangs, and an Iperf test
> ran successfully.
>
> Sameeh Jubran (2):
>    e1000: Fixing interrupts pace.
>    Revert "e1000: fix hang of win2k12 shutdown with flood ping"
>
>   hw/net/e1000.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
In general I support the idea to have the minimal limit
and drop original patch.

Though I'd better keep the same delay as it was. The limit
for physical card is good for physical card. They have
limitations which are not available in virtualization
world.

AFAIR I have used 250 as the number from the article
of the original author of ITR support as the best value.

Den