On 01/18/2019 07:33 AM, Andrea Bolognani wrote:
> On Thu, 2019-01-17 at 12:52 -0500, Cole Robinson wrote:
> [...]
>> @@ -1108,6 +1110,8 @@ struct virQEMUCapsStringFlags virQEMUCapsObjectTypes[] = {
>> { "vfio-ap", QEMU_CAPS_DEVICE_VFIO_AP },
>> { "zpci", QEMU_CAPS_DEVICE_ZPCI },
>> { "memory-backend-memfd", QEMU_CAPS_OBJECT_MEMORY_MEMFD },
>> + {"virtio-blk-pci-transitional", QEMU_CAPS_DEVICE_VIRTIO_BLK_TRANSITIONAL},
>> + {"virtio-blk-pci-non-transitional", QEMU_CAPS_DEVICE_VIRTIO_BLK_NON_TRANSITIONAL},
>
> There should be whitespace before and after curly braces, for
> consistency with existing entries.
>
Indeed, I'll fix that in all the patches
> [...]
>
>> +++ b/src/qemu/qemu_capabilities.h
>> @@ -504,6 +504,8 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
>> /* 325 */
>> QEMU_CAPS_OBJECT_MEMORY_FILE_PMEM, /* -object memory-backend-file,pmem= */
>> QEMU_CAPS_DEVICE_NVDIMM_UNARMED, /* -device nvdimm,unarmed= */
>> + QEMU_CAPS_DEVICE_VIRTIO_BLK_TRANSITIONAL, /* -device virtio-blk-pci-transitional */
>> + QEMU_CAPS_DEVICE_VIRTIO_BLK_NON_TRANSITIONAL, /* -device virtio-blk-pci-non-transitional */
>
> A bit more verbose, but I think we should go for
>
> QEMU_CAPS_DEVICE_VIRTIO_BLK_PCI_{,NON_}TRANSITIONAL
>
> since there are several non-PCI variants of VirtIO devices.
>
Sure sounds good
> It'd also be nice if adding the capabilities and wiring up the
> command line generation bits happened in separate patches.
>
> [...]
>
OK
>> +static int
>> +qemuBuildVirtioTransitional(virBufferPtr buf,
>> + const char *baseName,
>> + virQEMUCapsPtr qemuCaps,
>> + virDomainDeviceAddressType type,
>> + int model,
>> + virDomainDeviceType devtype)
>> +{
>> + int tmodel_cap, ntmodel_cap;
>> + bool has_tmodel, has_ntmodel;
>> +
>> + if (qemuBuildVirtioDevStr(buf, baseName, type) < 0)
>> + return -1;
>> +
>> + switch (devtype) {
>> + case VIR_DOMAIN_DEVICE_DISK:
>> + has_tmodel = model == VIR_DOMAIN_DISK_MODEL_VIRTIO_TRANSITIONAL;
>> + has_ntmodel = model == VIR_DOMAIN_DISK_MODEL_VIRTIO_NON_TRANSITIONAL;
>> + tmodel_cap = QEMU_CAPS_DEVICE_VIRTIO_BLK_TRANSITIONAL;
>> + ntmodel_cap = QEMU_CAPS_DEVICE_VIRTIO_BLK_NON_TRANSITIONAL;
>> + break;
>
> I like this approach much better than the one used in the RFC,
> eg. passing two booleans to the function. Nice!
>
> What I don't like is that you're building this fairly thin wrapper
> around qemuBuildVirtioDevStr() when IMHO you should rather be
> agumenting the original function - mostly because the new name is
> not nearly as good :) Do you think you could make that happen?
>
Hmm, seems weird to make call sites that will never support the
transitional naming (virtio-keyboard/mouse/tablet/gpu) have to call into
this function, passing DEVICE_TYPE etc. I can split the transitional
bits into their own function and not have it wrap BuildVirtioDevStr but
be a follow on, so for example:
if (qemuBuildVirtioDevStr(...) < 0)
goto error;
if (qemuBuildVirtioTransitionalStr(...) < )
goto error;
Does that work?
> [...]
>> + if (type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI &&
>> + (has_tmodel || has_ntmodel)) {
>> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> + _("virtio transitional models are not supported "
>> + "for address type=%s"),
>
> s/transitional/(non-)transitional/
>
> [...]
>> + 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'll respond separately
> [...]
>> @@ -723,6 +723,8 @@ qemuDomainDeviceCalculatePCIConnectFlags(virDomainDeviceDefPtr dev,
>> case VIR_DOMAIN_DEVICE_DISK:
>> switch ((virDomainDiskBus) dev->data.disk->bus) {
>> case VIR_DOMAIN_DISK_BUS_VIRTIO:
>> + if (dev->data.disk->model == VIR_DOMAIN_DISK_MODEL_VIRTIO_TRANSITIONAL)
>> + return pciFlags;
>
> Perhaps a short comment about how transitional VirtIO devices can
> only be plugged into conventional PCI slots would be appropriate
> here, for the benefit of those looking at the code years from now :)
>
This same pattern is duplicated in the rest of the series, seems weird
to comment one site, but commenting all of them is overkill. I guess
commenting one site is the middle ground unless you have a better idea
of where to put the comment
Thanks for the review
- Cole
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