yahoo-eng-team team mailing list archive

[Masanori Kuroha <2116995@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

Overview:
If vmcoreinfo feature is enabled and the Guest(VM) OS includes the kernel module qemu_fw_cfg, enabling SEV will cause kernel panic.

Details:
Currently, vmcoreinfo is enabled by default[1].

In addition, the module qemu_fw_cfg is included in the RHEL-based image (confirmed environment is Rocky Linux) as a builtin.
```
$ modinfo qemu_fw_cfg
name:           qemu_fw_cfg
filename:       (builtin)
license:        GPL
file:           drivers/firmware/qemu_fw_cfg
description:    QEMU fw_cfg sysfs support
author:         Gabriel L. Somlo <somlo@xxxxxxx>
```

At this time, kernel panic occurred when we created a VM with SEV enabled.
Guess: Conflict between SEV, which limits DMA, and qemu_fw_cfg, which is supposed to use DMA.
Incidentally, when we set vmcoreinfo feature to disable, we succeeded in starting the SEV-enabled VM in the same environment.

References:
[1] https://github.com/openstack/nova/commit/740e6f09bf5a3e5ab3c6dd6d412dd1fe33f81d9f

Environment:
Image: Rocky Linux 9.5
OpenStack: Dalmatial release (2024.2)

** Affects: nova
     Importance: Undecided
         Status: New

** Description changed:

  Overview:
  If vmcoreinfo feature is enabled and the Guest(VM) OS includes the kernel module qemu_fw_cfg, enabling SEV will cause kernel panic.
  
  Details:
  Currently, vmcoreinfo is enabled by default[1].
  
  In addition, the module qemu_fw_cfg is included in the RHEL-based image (confirmed environment is Rocky Linux) as a builtin.
  ```
  $ modinfo qemu_fw_cfg
  name:           qemu_fw_cfg
  filename:       (builtin)
  license:        GPL
  file:           drivers/firmware/qemu_fw_cfg
  description:    QEMU fw_cfg sysfs support
  author:         Gabriel L. Somlo <somlo@xxxxxxx>
  ```
  
- At this time, kernel panic occurred when I started a VM with SEV enabled.
+ At this time, kernel panic occurred when we created a VM with SEV enabled.
  Guess: Conflict between SEV, which limits DMA, and qemu_fw_cfg, which is supposed to use DMA.
- Incidentally, when we set vmcoreinfo to disable, I succeeded in starting the SEV-enabled VM in the same environment.
+ Incidentally, when we set vmcoreinfo feature to disable, we succeeded in starting the SEV-enabled VM in the same environment.
  
  References:
  [1] https://github.com/openstack/nova/commit/740e6f09bf5a3e5ab3c6dd6d412dd1fe33f81d9f
  
  Environment:
  Image: Rocky Linux 9.5
  OpenStack: Dalmatial release (2024.2)

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https://bugs.launchpad.net/bugs/2116995

Title:
  Unable to enable SEV on RHEL image

Status in OpenStack Compute (nova):
  New

Bug description:
  Overview:
  If vmcoreinfo feature is enabled and the Guest(VM) OS includes the kernel module qemu_fw_cfg, enabling SEV will cause kernel panic.

  Details:
  Currently, vmcoreinfo is enabled by default[1].

  In addition, the module qemu_fw_cfg is included in the RHEL-based image (confirmed environment is Rocky Linux) as a builtin.
  ```
  $ modinfo qemu_fw_cfg
  name:           qemu_fw_cfg
  filename:       (builtin)
  license:        GPL
  file:           drivers/firmware/qemu_fw_cfg
  description:    QEMU fw_cfg sysfs support
  author:         Gabriel L. Somlo <somlo@xxxxxxx>
  ```

  At this time, kernel panic occurred when we created a VM with SEV enabled.
  Guess: Conflict between SEV, which limits DMA, and qemu_fw_cfg, which is supposed to use DMA.
  Incidentally, when we set vmcoreinfo feature to disable, we succeeded in starting the SEV-enabled VM in the same environment.

  References:
  [1] https://github.com/openstack/nova/commit/740e6f09bf5a3e5ab3c6dd6d412dd1fe33f81d9f

  Environment:
  Image: Rocky Linux 9.5
  OpenStack: Dalmatial release (2024.2)

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