[Bug 1882241] Re: file transfer over cifs to 64bit guest corrupts large files

[timsoft <1882241@bugs.launchpad.net>]

thanks for the suggestion. I tried using netcat (nc) to transfer a large file from host to guest, and also from fileserver to guest with the problematic i82551 emulated network adapter on the host and the files transfered reliably. (correct md5sum 3 out of 3 attempts)
I also tried md5sum of the same file mounted on the guest fs as before and it still corrupts the data.
this seems to imply there is something in the cifs implementation which reacts adversly with this particular combination of virtual network hardware, the fact it works with the vmxnet3 emulated card, would support that conclusion.

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https://bugs.launchpad.net/bugs/1882241

Title:
  file transfer over cifs to 64bit guest corrupts large files

Status in QEMU:
  New

Bug description:
  qemu 4.0 compiled fom source.
  vm called by
  qemu-system-x86_64 -cpu qemu64 -smp 4 -m 4G -drive file=/data/images/slack14.2_64bit_test.qcow2,format=qcow2 -cdrom /mnt/smb1/slackware/iso/slackware64-14.2-install-dvd.iso -boot c -net nic,macaddr=02:00:00:11:11:17,model=i82551 -net bridge,br=br0 -enable-kvm -k en-gb -display vnc=:3 -monitor telnet:localhost:7103,server,nowait,nodelay

  copying large files eg 2.4gb or reading them on a cifs mount in the guest causes corruption every time. For smaller files 40-60mb corruption is more than 50% of the time. tested by md5sum on cifs server, or on host machine vs. on guest vm.
  corruption is seen only with 64bit guest using cifs with i82551 emulated network device
  ie. 32bit guest using cifs with i82551 emulated network device gives no corruption.

  changing the emulated device to vmxnet3 removes the data corruption
  (see below)

  qemu-system-x86_64 -cpu qemu64 -smp 4 -m 4G -drive
  file=/data/images/slack14.2_64bit_test.qcow2,format=qcow2 -cdrom
  /mnt/smb1/slackware/iso/slackware64-14.2-install-dvd.iso -boot c -net
  nic,macaddr=02:00:00:11:11:17,model=vmxnet3 -net bridge,br=br0
  -enable-kvm -k en-gb -display vnc=:3 -monitor
  telnet:localhost:7103,server,nowait,nodelay

  this corruption is repeatable. ie. I created new vm, call using top example, installed 64bit linux, mounted cifs share and copied 2.4gb file to /tmp then run md5sum "filecopied"
  the md5sum is different every time. copy same file to the host, or to a 32bit guest with the same virtual network device and bridge and md5sums are correct. The host pysical network adapter is
  lspci|grep Ether
  1e:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 11)

  physically connected via gigabit ethernet to cifs server (via gigabit
  switch)

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