[PATCH v4 0/6] hw/arm/virt: kvm: allow gicv3 by default if v2 cannot work

[Eric Auger]

At the moment if the end-user does not specify the gic-version along
with KVM acceleration, v2 is set by default. However most of the
systems now have GICv3 and sometimes they do not support GICv2
compatibility. In that case we now end up with the following error:

"qemu-system-aarch64: Initialization of device kvm-arm-gic failed:
error creating in-kernel VGIC: No such device
Perhaps the host CPU does not support GICv2?"

since "1904f9b5f1  hw/intc/arm_gic_kvm: Don't assume kernel can
provide a GICv2" which already allowed to output an explicit error
message.

This patch keeps the default v2 selection in all cases except
in the KVM accelerated mode when v2 cannot work:
- either because the host does not support v2 in-kernel emulation or
- because more than 8 vcpus were requested.

Those cases did not work anyway so we do not break any compatibility.
Now we get v3 selected in such a case.

Best Regards

Eric

This series can be found at:
https://github.com/eauger/qemu/tree/v4.2.0-gic-version-v4

History:

v3 -> v4:
- do not probe the host GIC version if kernel-irqchip=off
- In KVM mode / userspace irqchip we immediatly output an error
  in case the end-user explicitly selected v3. Also we warn the
  end-user about the weird usage of host in that case (only
  userspace GICv2 is supported).
- Removed R-b on last 2 patches

v2 -> v3:
- replaced defines by VirtGICType enum type
- fixed some style issue
- collected Richard and Dres's R-b
  except on "hw/arm/virt: Introduce VirtGICType enum type" just
  to make sure this matches their expectation.

RFC -> v1:
- 1904f9b5f1  hw/intc/arm_gic_kvm: Don't assume kernel can
provide a GICv2" now has landed upstream
- Fix gic-version description
- Introduce finalize_gic_version and use switch/cases
- take into account smp value


Eric Auger (6):
  hw/arm/virt: Document 'max' value in gic-version property description
  hw/arm/virt: Introduce VirtGICType enum type
  hw/arm/virt: Introduce finalize_gic_version()
  target/arm/kvm: Let kvm_arm_vgic_probe() return a bitmap
  hw/arm/virt: kvm: Restructure finalize_gic_version()
  hw/arm/virt: kvm: allow gicv3 by default if v2 cannot work

 include/hw/arm/virt.h |  12 +++-
 target/arm/kvm_arm.h  |   3 +
 hw/arm/virt.c         | 146 +++++++++++++++++++++++++++++++++---------
 target/arm/kvm.c      |  14 ++--
 4 files changed, 135 insertions(+), 40 deletions(-)

-- 
2.20.1