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

[Michal Prívozník]

On 4/13/23 08:07, Zhenzhong Duan wrote:
> virsh command domxml-to-native failed with below error but start
> command suceed 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.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan at intel.com>
> ---
>  src/qemu/qemu_domain.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> 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;
> +        }
> +    }
>  

The same happens in qemuHostdevPreparePCIDevicesCheckSupport(). Should
we remove the code from there and leave just checks there? I mean, if
choosing the backend is moved here, as you suggests, then
qemuHostdevPreparePCIDevicesCheckSupport() shouldn't ever see a hostdev
with VIR_DOMAIN_HOSTDEV_PCI_BACKEND_DEFAULT. Except when the host
doesn't support VFIO. So maybe just drop the code that sets backend an
replace it with a virReportError();

Michal