From mboxrd@z Thu Jan  1 00:00:00 1970
From: Charles Duffy <Charles_Duffy@messageone.com>
Subject: e1000 PXE breakage bisected down in kvm-userspace
Date: Mon, 04 Aug 2008 16:02:17 -0500
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Per subject. "git bisect run" script (and libvirt xml helper) attached.

> 87b5acf6125d205119e3194c02ed6e71715517dc is first bad commit
> commit 87b5acf6125d205119e3194c02ed6e71715517dc
> Author: Anthony Liguori <aliguori@us.ibm.com>
> Date:   Wed May 7 13:09:40 2008 -0500
> 
>     kvm: qemu: stop dropping so many RX packets in tap
>     
>     Normally, tap always reads packets and simply lets the client drop them if it
>     cannot receive them.  For virtio-net, this results in massive packet loss and
>     about an 80% performance loss in TCP throughput.
>     
>     This patch modifies qemu_send_packet() to only deliver a packet to a VLAN
>     client if it doesn't have a fd_can_read method or the fd_can_read method
>     indicates that it can receive packets.  We also return a status of whether
>     any clients were able to receive the packet.
>     
>     If no clients were able to receive a packet, we buffer the packet until a
>     client indicates that it can receive packets again.
>     
>     This patch also modifies the tap code to only read from the tap fd if at least
>     one client on the VLAN is able to receive a packet.
>     
>     Finally, this patch changes the tap code to drain all possible packets from
>     the tap device when the tap fd is readable.
>     
>     Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
>     Signed-off-by: Avi Kivity <avi@qumranet.com>
> 
> :040000 040000 648a4d52612e0ce68167f279d30bd3f4ec0f22f4 85352e7b252abb1247af2f024eab10a3e8ec0084 M	qemu

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Content-Type: text/plain;
 name="kvm-e1000-test"
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Content-Disposition: inline;
 filename="kvm-e1000-test"

#!/bin/bash

LIBVIRT_VM_NAME=com.m1dev.syseng.cduffy.boottest
LIBVIRT_VM_XML=/local/src/kvm-e1000-test.xml
VM_CONSOLE_LOG=/local/src/kvm-e1000-test.out
SRC_TREE_USER=/local/src/kvm-userspace
SRC_TREE_KERN=/local/src/kvm

set -e

function try_patch() {
	local PATCH="$1"
	if patch -f -p0 --dry-run < "$PATCH" ; then
		patch -p0 < "$PATCH"
	fi
	return 0
}

function cleanup() {
	virsh destroy ${LIBVIRT_VM_NAME} || true
	rm -f ${VM_CONSOLE_LOG}
}

function test_failure() {
	exit 125
}
trap test_failure 0

cd ${SRC_TREE_USER}
git reset --hard
try_patch ../kvm-userspace.centos5_compat.kvm-69.patch
try_patch ../kvm-userspace.centos5_compat.kvm-70.patch
./configure \
	--prefix=/opt/kvm.git \
	--kerneldir=/usr/src/kernels/2.6.18-92.1.6.el5-x86_64 \
	--disable-gfx-check \
	--disable-sdl
make WANT_MODULE= KERNELDIR=${SRC_TREE_KERN} clean
make WANT_MODULE= KERNELDIR=${SRC_TREE_KERN}
make WANT_MODULE= KERNELDIR=${SRC_TREE_KERN} install
git reset --hard

cleanup
virsh create "${LIBVIRT_VM_XML}"
sleep 5
if [ ! -e "${VM_CONSOLE_LOG}" ] ; then
	echo 'ERR: No virtual console detected' >&2
	exit 125
fi

echo 'Waiting for kernel splash notice' >&2
trap - 0
trap cleanup 0
COUNTDOWN=60
while [ "$COUNTDOWN" -gt 0 ] ; do
	echo -n '.' >&2
	COUNTDOWN="$(($COUNTDOWN - 1))"
	sleep 1
	if grep -e 'Linux version' ${VM_CONSOLE_LOG} ; then
		echo 'OK: net boot succeeded' >&2
		exit 0
	fi
done
echo 'BAD: no net boot detected' >&2
exit 1

--------------010300010104020702020607
Content-Type: text/xml;
 name="kvm-e1000-test.xml"
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Content-Disposition: inline;
 filename="kvm-e1000-test.xml"

<domain type='kvm'>
  <name>com.m1dev.syseng.cduffy.boottest</name>
  <uuid>70d09285-f451-426d-8ab0-4c4810616ce6</uuid>
  <memory>768432</memory>
  <currentMemory>768432</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='i686' machine='pc'>hvm</type>
    <boot dev='network'/>
  </os>
  <features>
    <acpi/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/opt/kvm.git/bin/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
      <source file='/local/VM/com.m1dev.syseng.cduffy.boottest.raw'/>
      <target dev='sda' bus='scsi'/>
    </disk>
    <interface type='network'>
      <mac address='00:16:3e:fe:cb:31'/>
      <source network='com.m1dev.syseng.cduffy'/>
      <model type='e1000'/>
    </interface>
    <console type='file'>
      <source path='/local/src/kvm-e1000-test.out'/>
      <target port='0'/>
    </console>
  </devices>
</domain>

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