On 01/18/2019 07:33 AM, Andrea Bolognani wrote:
> On Thu, 2019-01-17 at 12:52 -0500, Cole Robinson wrote:
>> + if (has_tmodel) {
>> + if (virQEMUCapsGet(qemuCaps, tmodel_cap))
>> + virBufferAddLit(buf, "-transitional");
>> +
>> + /* No error for if -transitional is not supported: our address
>> + * allocation will force the device into plain PCI bus, which
>> + * is functionally identical to standard 'virtio-XXX' behavior
>> + */
>> + } else if (has_ntmodel) {
>> + if (virQEMUCapsGet(qemuCaps, ntmodel_cap)) {
>> + virBufferAddLit(buf, "-non-transitional");
>> + } else if (virQEMUCapsGet(qemuCaps,
>> + QEMU_CAPS_VIRTIO_PCI_DISABLE_LEGACY)) {
>> + virBufferAddLit(buf, ",disable-legacy=on");
>> + } else {
>> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>> + _("virtio non-transitional model not supported "
>> + "for this qemu"));
>> + return -1;
>> + }
>> + }
>
> Would it make sense to be more explicit here? Current versions of
> QEMU default to disable-modern=off,disable-legacy=off for virtio-pci
> devices plugged into conventional PCI slots, but unless I'm mistaken
> that was not always the case, so it would perhaps be preferrable to
> not rely on that behavior and always explicitly set both disable-*
> options when the new devices are not available; if the options
> themselves are not available, then we should error out.
>
I don't know enough to say, CCing ehabkost and danpb for more eyes
- Cole
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