There are couple of examples where this knob would be useful:

https://bugs.launchpad.net/qemu/+bug/1846451

(look for those cmd line passthrough hacks), and one pretty recent
request:

https://listman.redhat.com/archives/libvir-list/2022-June/232611.html

The last patch uses info from Kraxel's patch (which he posted after our
private discussion):

https://lists.gnu.org/archive/html/qemu-devel/2022-07/msg01733.html

Michal Prívozník (5):
  tests: Update hostdev-usb-* hostdev-pci-* xml2xml and xml2argv tests
  conf: Introduce @guestReset to hostdev's <source/>
  qemu_capabilities: Track usb-host.guest-resets-all capability
  qemu_validate: Validate that QEMU's capable of guestReset
  qemu: Generate cmd line for guestReset

 docs/formatdomain.rst                         | 15 +++++++-
 src/conf/domain_conf.c                        | 18 +++++++++
 src/conf/domain_conf.h                        | 13 +++++++
 src/conf/schemas/domaincommon.rng             |  9 +++++
 src/qemu/qemu_capabilities.c                  |  2 +
 src/qemu/qemu_capabilities.h                  |  1 +
 src/qemu/qemu_command.c                       | 21 ++++++++++
 src/qemu/qemu_validate.c                      |  8 ++++
 .../qemucapabilitiesdata/caps_3.1.0.ppc64.xml |  1 +
 .../caps_3.1.0.x86_64.xml                     |  1 +
 .../caps_4.0.0.aarch64.xml                    |  1 +
 .../qemucapabilitiesdata/caps_4.0.0.ppc64.xml |  1 +
 .../caps_4.0.0.riscv32.xml                    |  1 +
 .../caps_4.0.0.riscv64.xml                    |  1 +
 .../qemucapabilitiesdata/caps_4.0.0.s390x.xml |  1 +
 .../caps_4.0.0.x86_64.xml                     |  1 +
 .../caps_4.1.0.x86_64.xml                     |  1 +
 .../caps_4.2.0.aarch64.xml                    |  1 +
 .../qemucapabilitiesdata/caps_4.2.0.ppc64.xml |  1 +
 .../qemucapabilitiesdata/caps_4.2.0.s390x.xml |  1 +
 .../caps_4.2.0.x86_64.xml                     |  1 +
 .../caps_5.0.0.aarch64.xml                    |  1 +
 .../qemucapabilitiesdata/caps_5.0.0.ppc64.xml |  1 +
 .../caps_5.0.0.riscv64.xml                    |  1 +
 .../caps_5.0.0.x86_64.xml                     |  1 +
 .../caps_5.1.0.x86_64.xml                     |  1 +
 .../caps_5.2.0.aarch64.xml                    |  1 +
 .../qemucapabilitiesdata/caps_5.2.0.ppc64.xml |  1 +
 .../caps_5.2.0.riscv64.xml                    |  1 +
 .../caps_5.2.0.x86_64.xml                     |  1 +
 .../caps_6.0.0.aarch64.xml                    |  1 +
 .../caps_6.0.0.x86_64.xml                     |  1 +
 .../caps_6.1.0.x86_64.xml                     |  1 +
 .../caps_6.2.0.aarch64.xml                    |  1 +
 .../caps_6.2.0.x86_64.xml                     |  1 +
 .../caps_7.0.0.aarch64.xml                    |  1 +
 .../qemucapabilitiesdata/caps_7.0.0.ppc64.xml |  1 +
 .../caps_7.0.0.x86_64.xml                     |  1 +
 .../caps_7.1.0.x86_64.xml                     |  1 +
 .../hostdev-pci-address-device.args           | 34 -----------------
 ...tdev-pci-address-device.x86_64-latest.args | 38 +++++++++++++++++++
 .../hostdev-pci-address-device.xml            |  2 +-
 .../qemuxml2argvdata/hostdev-pci-address.args | 33 ----------------
 .../hostdev-pci-address.x86_64-latest.args    | 37 ++++++++++++++++++
 .../qemuxml2argvdata/hostdev-pci-address.xml  |  2 +-
 .../hostdev-usb-address-device-boot.args      | 34 -----------------
 ...usb-address-device-boot.x86_64-latest.args | 38 +++++++++++++++++++
 .../hostdev-usb-address-device-boot.xml       |  2 +-
 .../hostdev-usb-address-device.args           | 34 -----------------
 ...tdev-usb-address-device.x86_64-latest.args | 38 +++++++++++++++++++
 .../hostdev-usb-address-device.xml            |  2 +-
 .../qemuxml2argvdata/hostdev-usb-address.args | 33 ----------------
 .../hostdev-usb-address.x86_64-latest.args    | 37 ++++++++++++++++++
 .../qemuxml2argvdata/hostdev-usb-address.xml  |  4 +-
 tests/qemuxml2argvtest.c                      | 10 ++---
 ... => hostdev-pci-address.x86_64-latest.xml} |  7 +++-
 ... => hostdev-usb-address.x86_64-latest.xml} |  9 +++--
 tests/qemuxml2xmltest.c                       |  4 +-
 58 files changed, 329 insertions(+), 187 deletions(-)
 delete mode 100644 tests/qemuxml2argvdata/hostdev-pci-address-device.args
 create mode 100644 tests/qemuxml2argvdata/hostdev-pci-address-device.x86_64-latest.args
 delete mode 100644 tests/qemuxml2argvdata/hostdev-pci-address.args
 create mode 100644 tests/qemuxml2argvdata/hostdev-pci-address.x86_64-latest.args
 delete mode 100644 tests/qemuxml2argvdata/hostdev-usb-address-device-boot.args
 create mode 100644 tests/qemuxml2argvdata/hostdev-usb-address-device-boot.x86_64-latest.args
 delete mode 100644 tests/qemuxml2argvdata/hostdev-usb-address-device.args
 create mode 100644 tests/qemuxml2argvdata/hostdev-usb-address-device.x86_64-latest.args
 delete mode 100644 tests/qemuxml2argvdata/hostdev-usb-address.args
 create mode 100644 tests/qemuxml2argvdata/hostdev-usb-address.x86_64-latest.args
 rename tests/qemuxml2xmloutdata/{hostdev-pci-address.xml => hostdev-pci-address.x86_64-latest.xml} (86%)
 rename tests/qemuxml2xmloutdata/{hostdev-usb-address.xml => hostdev-usb-address.x86_64-latest.xml} (83%)

-- 
2.35.1