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

[Michael S. Tsirkin]

On Thu, Mar 17, 2016 at 09:37:56AM +0200, 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.


Interesting. There's actually a kvm hack to work-around
this in older guests. We always assumed this is a guest bug,
but it might be worth testing whether the below patch is
still required after fixing qemu.

commit 184564efae4d775225c8fe3b762a56956fb1f827
Author: Zhang Haoyu <address@hidden>
Date:   Thu Sep 11 16:47:04 2014 +0800

    kvm: ioapic: conditionally delay irq delivery duringeoi broadcast
    
    Currently, we call ioapic_service() immediately when we find the irq is 
still




> 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(-)
> 
> -- 
> 2.5.0
>