[PATCH v2 5/9] qemu: Deny all but VFIO PCI backends in hostdev prepare phase

[Michal Prívozník]

On 4/24/23 13:11, Martin Kletzander wrote:
> On Mon, Apr 24, 2023 at 12:41:44PM +0200, Michal Privoznik wrote:
>> We used to support KVM and VFIO style of PCI assignment. The
>> former was dropped in v5.7.0-rc1~103 and thus we only support
>> VFIO. All other backends lead to an error (see
>> qemuBuildPCIHostdevDevProps(), or qemuBuildPCIHostdevDevStr() as
>> it used to be called in the era of aforementioned commit).
>>
>> Might as well report the error in prepare phase and save hassle
>> of proceeding with device preparation (e.g. in case of hotplug
>> overriding the device's driver, setting seclabels, etc.).
>>
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>> src/qemu/qemu_domain.c | 7 +++----
>> 1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
>> index 58cd3dd710..72f36c807b 100644
>> --- a/src/qemu/qemu_domain.c
>> +++ b/src/qemu/qemu_domain.c
>> @@ -11326,12 +11326,11 @@
>> qemuDomainPrepareHostdevPCI(virDomainHostdevDef *hostdev,
>>         break;
>>
>>     case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_KVM:
>> -        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>> -                       _("host doesn't support legacy PCI
>> passthrough"));
>> -        return false;
>> -
>>     case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_XEN:
>>     case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_TYPE_LAST:
>> +        virReportError(VIR_ERR_INTERNAL_ERROR,
>> +                       _("invalid PCI passthrough type '%1$s'"),
>> +                      
>> virDomainHostdevSubsysPCIBackendTypeToString(*backend));
> 
> This is a bit misleading as it is not "invalid", it's just unsupported,
> and on top of that you're changing it to internal error and I think it
> should still be CONFIG_UNSUPPORTED, at least for KVM and XEN.  _LAST
> (and possibly default:) is still an internal error of course.

Fair enough. How about this then?

    case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_KVM:
        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                       _("host doesn't support legacy PCI passthrough"));
        return false;

    case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_XEN:
        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                       _("QEMU does not support device assignment mode '%1$s'"),
                       virDomainHostdevSubsysPCIBackendTypeToString(*backend));
        return false;

    default:
    case VIR_DOMAIN_HOSTDEV_PCI_BACKEND_TYPE_LAST:
        virReportEnumRangeError(virDomainHostdevSubsysPCIBackendType, *backend);
        break;
    }

I have this as a fixup patch on the top of this one (well, this is how
it looks after the patch), locally.

Michal