qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH for 2.5 1/1] e1000: fix hang of win2k12 shutdown


From: Denis V. Lunev
Subject: Re: [Qemu-devel] [PATCH for 2.5 1/1] e1000: fix hang of win2k12 shutdown with flood ping
Date: Fri, 27 Nov 2015 09:50:34 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0

On 11/27/2015 09:48 AM, Denis V. Lunev wrote:
e1000 driver in Win2k12 is really well rotten. It 100% hangs on shutdown
of UP VM under flood ping. The guest checks card state and reinjects
itself interrupt in a loop. This is fatal for UP machine.

There is no good way to fix this misbehavior but to kludge it. The
emulation has interrupt throttling register aka ITR which limits
interrupt rate and allows the guest to proceed this phase.
There is no problem with this kludge for Linux guests - it adjust the
value of it itself.

On the other hand according to the initial research in
     commit e9845f0985f088dd01790f4821026df0afba5795
     Author: Vincenzo Maffione <address@hidden>
     Date:   Fri Aug 2 18:30:52 2013 +0200

     e1000: add interrupt mitigation support

     ...

     Interrupt mitigation boosts performance when the guest suffers from
     an high interrupt rate (i.e. receiving short UDP packets at high packet
     rate). For some numerical results see the following link
     http://info.iet.unipi.it/~luigi/papers/20130520-rizzo-vm.pdf

this should also boost performance a bit.

See https://bugzilla.redhat.com/show_bug.cgi?id=874406 for additional
details.

Signed-off-by: Denis V. Lunev <address@hidden>
CC: Vincenzo Maffione <address@hidden>
CC: Stefan Hajnoczi <address@hidden>
---
  hw/net/e1000.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index c877e06..0af528f 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -447,6 +447,9 @@ static void e1000_reset(void *opaque)
          e1000_link_down(d);
      }
+ /* Throttle interrupts to allow poor Win 2012 to shutdown */
+    d->mac_reg[ITR] = 250;
+
      /* Some guests expect pre-initialized RAH/RAL (AddrValid flag + MACaddr) 
*/
      d->mac_reg[RA] = 0;
      d->mac_reg[RA + 1] = E1000_RAH_AV;
Intel manual says about ITR that " A initial suggested range is 651-5580 (28Bh - 15CCh)."
Should we use something other than 250? :)

http://www.intel.com/content/www/us/en/embedded/products/networking/pci-pci-x-family-gbe-controllers-software-dev-manual.html

Den



reply via email to

[Prev in Thread] Current Thread [Next in Thread]