[PATCH v2] qemu: Fix domxml-to-native command failure

[Michal Prívozník]

On 4/14/23 07:34, Zhenzhong Duan wrote:
> virsh command domxml-to-native failed with below error but start
> command succeed for same domain xml.
> 
> "internal error: invalid PCI passthrough type 'default'"
> 
> If host PCI device's driver attribute isn't defined in domain xml,
> qemu driver will choose a proper value based on host environment
> before starting qemu process. But this is missed in domxml-to-native
> command, add the same logic so domxml-to-native could pass and replace
> the relevant code in qemuHostdevPreparePCIDevicesCheckSupport() with
> an error report.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan at intel.com>
> ---
> v2: replace setting with an error report, suggested by Michal
> 
>  src/qemu/qemu_domain.c  | 11 +++++++++++
>  src/qemu/qemu_hostdev.c |  8 ++++----
>  2 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 63b13b6875c9..517c90f93f0a 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -11274,6 +11274,17 @@ qemuDomainPrepareHostdev(virDomainHostdevDef *hostdev,
>              }
>          }
>      }
> +    if (hostdev->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS &&
> +        hostdev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI) {
> +        bool supportsPassthroughVFIO = qemuHostdevHostSupportsPassthroughVFIO();
> +        virDomainHostdevSubsysPCIBackendType *backend = &hostdev->source.subsys.u.pci.backend;
> +
> +        if (*backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_DEFAULT &&
> +            supportsPassthroughVFIO &&
> +            virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE_VFIO_PCI)) {
> +            *backend = VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO;
> +        }
> +    }
>  
>      return 0;
>  }
> diff --git a/src/qemu/qemu_hostdev.c b/src/qemu/qemu_hostdev.c
> index 45cd1066f0a5..305a323a0769 100644
> --- a/src/qemu/qemu_hostdev.c
> +++ b/src/qemu/qemu_hostdev.c
> @@ -175,15 +175,15 @@ qemuHostdevPreparePCIDevicesCheckSupport(virDomainHostdevDef **hostdevs,
>          case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_DEFAULT:
>              if (supportsPassthroughVFIO &&
>                  virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VFIO_PCI)) {
> -                *backend = VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO;
> +                virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                               _("qemuDomainPrepareHostdev() should have set backend "
> +                                 "to VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO"));

Ha! I've found one path where the backend is not set:
qemuDomainAttachHostPCIDevice(). So we need a bit more code movement.
But after that, this branch is effectively a dead code.

In fact, if we move things a bit a lot of code will become dead. So let
me respin with more patches.

Michal