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  1. RHEL
  2. RHEL-7135

[s390x] virtio-gpu blob option not functional

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    • qemu-kvm-8.2.0-1.el9
    • None
    • Moderate
    • rhel-sst-virtualization-hwe
    • ssg_virtualization
    • 16
    • 20
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    • Bug Fix
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      .`blob` resources now work correctly for `virtio-gpu` on IBM Z

      Previously, the `virtio-gpu` device was incompatible with `blob` memory resources on IBM Z systems. As a consequence, if you configured a virtual machine (VM) with `virtio-gpu` on an IBM Z host to use `blob` resources, the VM did not have any graphical output.

      With this update, `virtio` devices have an optional `blob` attribute. Setting `blob` to `on` enables the use of `blob` resources in the device. This prevents the described problem in `virtio-gpu` devices, and can also accelerate the display path by reducing or eliminating copying of pixel data between the guest and host. Note that `blob` resource support requires QEMU version 6.1 or later.
      Show
      .`blob` resources now work correctly for `virtio-gpu` on IBM Z Previously, the `virtio-gpu` device was incompatible with `blob` memory resources on IBM Z systems. As a consequence, if you configured a virtual machine (VM) with `virtio-gpu` on an IBM Z host to use `blob` resources, the VM did not have any graphical output. With this update, `virtio` devices have an optional `blob` attribute. Setting `blob` to `on` enables the use of `blob` resources in the device. This prevents the described problem in `virtio-gpu` devices, and can also accelerate the display path by reducing or eliminating copying of pixel data between the guest and host. Note that `blob` resource support requires QEMU version 6.1 or later.
    • Done
    • s390x
    • Linux
    • 8.2.0
    • None

      Description of problem:
      Follow up on verified https://bugzilla.redhat.com/show_bug.cgi?id=2032406

      Using blob option for virtio-gpu doesn't work (no graphical output).

      Version-Release number of selected component (if applicable):
      Host kernel 5.14.0-350.el9.s390x
      Guest kernel kernel-5.14.0-348.el9.s390x
      libvirt-9.5.0-5.el9.s390x
      qemu-kvm-8.0.0-10.el9.s390x

      How reproducible:
      100%

      Steps to Reproduce:
      1. setenforce 0 (workaround for missing selinux label)
      2. confirm /dev/udmabuf is available
      3. start vm with graphics and memory backing, e.g. from libvirt
      ...
      <memoryBacking>
      <source type='memfd'/>
      </memoryBacking>
      ...
      <video>
      <model type='virtio' heads='1' primary='yes' blob='on'/>
      <alias name='video0'/>
      <address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0002'/>
      </video>
      ...
      4. Connect vnc client

      Actual results:
      No graphical output

      Expected results:
      Same as without blob=on, it works

      Additional info:
      It works when I don't use blob=on

              thuth@redhat.com Thomas Huth
              smitterl@redhat.com Sebastian Mitterle
              Sebastian Mitterle Sebastian Mitterle
              Jiří Herrmann Jiří Herrmann
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                Created:
                Updated:
                Resolved: