Re: e1000 PXE breakage bisected down in kvm-userspace

[Anthony Liguori <anthony@codemonkey.ws>]

Charles Duffy wrote:
> Per subject. "git bisect run" script (and libvirt xml helper) attached.

Does the problem go away if you make the e1000_can_receive() function 
always return 1?

Regards,

Anthony Liguori

>> 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