Bug 1359862

Upstream fixed this by commit:

commit 5ed7afa9de4e8d2b7e83fee334a0c3f2bddc6a48
Author: Stefan Berger <stefanb.com>
Date:   Tue Nov 17 19:44:13 2015 -0500

    tpm: adapt sysfs cancel path for new TPM driver
    
    This patch addresses BZ 1244895.
    
    Adapt the sysfs TPM command cancel path for the TPM driver that
    does not use a miscdevice anymore since Linux 4.0. Support old
    and new paths and check their availability.
    
    Add a mockup for the test cases to avoid the testing for
    availability of the cancel path.

$ git describe 5ed7afa9de4e8d2b7e83fee334a0c3f2bddc6a48
v1.2.21-67-g5ed7afa

1. On RHEL7, guest can't start successfully with tpm device, qemu version is qemu-kvm-rhev-2.6.0-17.el7.x86_64
# virsh start rhel7.2
error: Failed to start domain rhel7.2
error: unsupported configuration: The QEMU executable /usr/libexec/qemu-kvm does not support TPM backend type passthrough


2. On fedora, guest can start successfully with tpm device
1) The versions I used on fedora is:
# /usr/bin/qemu-system-x86_64 --version
QEMU emulator version 2.4.1 (qemu-2.4.1-5.fc23), Copyright (c) 2003-2008 Fabrice Bellard

# libvirtd --version
libvirtd (libvirt) 1.3.2

2) Guest can start successfully and qemu cml is:
-tpmdev passthrough,id=tpm-tpm0,path=/dev/fdset/2,cancel-path=/dev/fdset/3
-add-fd set=2,fd=29
-add-fd set=3,fd=30
-device tpm-tis,tpmdev=tpm-tpm0,id=tpm0



More info about guest xml and qemu command line:
1) The guest xml libvirt uses is:
    <tpm model='tpm-tis'>
      <backend type='passthrough'>
        <device path='/dev/tpm0'/>
      </backend>
      <alias name='tpm0'/>
    </tpm>

2) The complete qemu command line is as below in case I miss something above:
 /usr/bin/qemu-system-x86_64 -name rhel7 -S -machine pc-i440fx-2.4,accel=kvm,usb=off -cpu Opteron_G2,+popcnt,+monitor,+ht,+vme,-svm -m size=512000k,slots=16,maxmem=1524736k -realtime mlock=off -smp 4,sockets=4,cores=1,threads=1 -numa node,nodeid=0,cpus=0-3,mem=500 -uuid 7cae86d2-88a2-4c94-95ee-5fdf08e07370 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/usr/local/var/lib/libvirt/qemu/domain-rhel7/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=discard -no-hpet -no-shutdown -global PIIX4_PM.disable_s3=0 -global PIIX4_PM.disable_s4=0 -boot strict=on -device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x9.0x7 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive file=/90121/fjin/rhel7.2.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -netdev tap,fd=26,id=hostnet0,vhost=on,vhostfd=28 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:f1:2c:ed,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/usr/local/var/lib/libvirt/qemu/channel/target/domain-rhel7/org.qemu.guest_agent.0,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -chardev spicevmc,id=charchannel1,name=vdagent -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=com.redhat.spice.0 -tpmdev passthrough,id=tpm-tpm0,path=/dev/fdset/2,cancel-path=/dev/fdset/3 -add-fd set=2,fd=29 -add-fd set=3,fd=30 -device tpm-tis,tpmdev=tpm-tpm0,id=tpm0 -vnc 127.0.0.1:0 -device qxl-vga,id=video0,ram_size=67108864,vram_size=16777216,vgamem_mb=16,bus=pci.0,addr=0x2 -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8 -device pvpanic,ioport=1285 -msg timestamp=on

Reproduce this bug with libvirt-1.2.17-13.el7.x86_64, kernel-3.10.0-493.el7.x86_64 and upstream qemu(v2.7.0-217-g7263da7)

Steps:
1. Prepare a guest with tpm device:
# virsh dumpxml rhel7.3-0817
...
    <tpm model='tpm-tis'>
      <backend type='passthrough'>
        <device path='/dev/tpm0'/>
      </backend>
    </tpm>

2. Start guest
# virsh start rhel7.3-0817
error: Failed to start domain rhel7.3-0817
error: Could not open TPM device's cancel path /sys/class/misc/tpm0/device/cancel: No such file or directory

Verify this bug with libvirt-2.0.0-8.el7.x86_64 and upstream qemu(v2.7.0-217-g7263da7) 

And also test on two different kernel versions: 
For kerne-3.10.0-493.el7.x86_64, the tpm device cancel path is: /sys/class/tpm/tpm0/device/cancel
For kernel-3.10.0-229.el7.x86_64, the tpm device cancel path is:/sys/class/misc/tpm0/device/cancel

Steps:
1.Prepare a guest with tpm device:

# virsh dumpxml rhel7.3-0817

    <tpm model='tpm-tis'>
      <backend type='passthrough'>
        <device path='/dev/tpm0'/>
      </backend>
      <alias name='tpm0'/>
    </tpm>

2. Start guest

# virsh start rhel7.3-0817

3. Check qemu command line:

...-tpmdev passthrough,id=tpm-tpm0,path=/dev/fdset/3,cancel-path=/dev/fdset/4 -add-fd set=3,fd=30 -add-fd set=4,fd=32 -device tpm-tis,tpmdev=tpm-tpm0,id=tpm0...

4. Check the opened file descriptors:

For kerne-3.10.0-493.el7.x86_64:
# lsof /sys/class/tpm/tpm0/device/cancel
lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/1000/gvfs
      Output information may be incomplete.
COMMAND     PID USER   FD   TYPE DEVICE SIZE/OFF  NODE NAME
qemu-syst 15117 qemu   11w   REG   0,16     4096 10212 /sys/class/tpm/../../devices/pnp0/00:09/tpm/tpm0/../../../00:09/cancel
qemu-syst 15117 qemu   24w   REG   0,16     4096 10212 /sys/class/tpm/../../devices/pnp0/00:09/tpm/tpm0/../../../00:09/cancel


# lsof /dev/tpm0
lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/1000/gvfs
      Output information may be incomplete.
COMMAND     PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
qemu-syst 15117 qemu   10u   CHR 10,224      0t0 1143 /dev/tpm0
qemu-syst 15117 qemu   23u   CHR 10,224      0t0 1143 /dev/tpm0


For kernel-3.10.0-229.el7.x86_64:
# lsof /sys/class/misc/tpm0/device/cancel
COMMAND     PID USER   FD   TYPE DEVICE SIZE/OFF  NODE NAME
qemu-syst 31727 qemu   10w   REG   0,16     4096 10111 /sys/class/misc/../../devices/pnp0/00:0d/misc/tpm0/../../../00:0d/cancel
qemu-syst 31727 qemu   23w   REG   0,16     4096 10111 /sys/class/misc/../../devices/pnp0/00:0d/misc/tpm0/../../../00:0d/cancel

\ # lsof /dev/tpm0
COMMAND     PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
qemu-syst 31727 qemu    9u   CHR 10,224      0t0 1144 /dev/tpm0
qemu-syst 31727 qemu   22u   CHR 10,224      0t0 1144 /dev/tpm0

Test with builds qemu-kvm-1.5.3-125.el7.x86_64 and libvirt-2.0.0-9.el7.x86_64.

# virsh start mig1
error: Failed to start domain mig1
error: unsupported configuration: The QEMU executable /usr/libexec/qemu-kvm does not support TPM backend type passthrough

So it seems that qemu-kvm also doesn't support TPM passthrough device.

hi, Evan,

As you can see from the above comments 9 to 11, libvirt component implement this feature support in RHEL7.3, but qemu do not implement this feature in current RHEL7.3, qemu implement it in upstream now.


I have 2 concerns need to confirm with you:
1. from the comment 4 to 7, it seems we should test and verify this bug with qemu-kvm in RHEL OS, not with qemu-kvm-rhev in RHEL OS, right?

2. Can we move this libvirt bug to RHEL7.4 and add Testonly keyword? since qemu-kvm do not support this feature in RHEL7.3 now. Since this bug is from the Customer Portal, we'd like to double condirm with you if it is ok to deal this bug per current support status of libvirt and qemu.
And can we file one corresponding qemu bug to RHEL7.4 for better tracking?

Move this bug to RHEL7.4 with Testonly keyword for better tracking, since qemu do not implement this feature in downstream in RHEL7.3.

TPM is not supported in RHEL7.4 by either qemu-kvm-rhev or qemu-kvm. So move this bug to RHEL7.5

Thank you!
Here is the qemu-kvm-rhev rfe: https://bugzilla.redhat.com/show_bug.cgi?id=1327947

And here is the kcs documenting current support status:
https://access.redhat.com/solutions/2623641