On 06/13/2018 09:42 PM, Laine Stump wrote:
On 06/13/2018 07:16 AM, John Ferlan wrote:
On 06/13/2018 04:15 AM, Ján Tomko wrote:
Add a check during qemuDomainAttachDeviceConfig whether the new/incoming <hostdev ...> device would have an existing <address> already and if so fail the attach. This can happen if two hostdev's are added supplying the same address or if the new hostdev address could possibly be a duplicate of an existing SCSI <disk>.
Signed-off-by: John Ferlan <jferlan@redhat.com> --- src/qemu/qemu_driver.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index f0fb806fcd..ae8e0e898a 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -8015,6 +8015,12 @@ qemuDomainAttachDeviceConfig(virDomainDefPtr vmdef, _("device is already in the domain configuration")); return -1; } + if (dev->data.hostdev->info->type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE && + virDomainDefHasDeviceAddress(vmdef, dev->data.hostdev->info)) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("a device with the same address already exists ")); + return -1; + } This check feels out of place here. We should be checking for that in
On Tue, Jun 12, 2018 at 10:32:06AM -0400, John Ferlan wrote: postParse. Do we have the same problem on domain startup?
I've avoided new post parse checks due to the domain disappearing phenomena.
The difference with this is that any existing domain with this error would have failed to start qemu in previous versions, so it surely would have been fixed. And assignment of addresses to PCI devices that are "coldplugged" (ie those that are added individually with AttachDevice, but that are only added to the persistent config, *not* to the running guest, ie "CONFIG") is handled by a manually added call to virDomainDefPostParse() that is called directly from qemuDomainAttachDeviceConfig:
qemuDomainAttachDeviceConfig virDomainDefPostParse qemuDomainDefAssignAddresses (aka assignAddressCallback) qemuDomainAssignAddresses
Is there a reason why SCSI addresses aren't assigned by the same function. If we did that then at least everyone would have the same set of problems :-P)
Not 100% sure of any reason other than perhaps the "relationship" between SCSI hostdev and SCSI disk. The generated address for a <disk> is based on the def->dst (see virDiskNameToIndex). A dst of "sda" would equate to controller=0 and unit=0. A <hostdev> will "find" a spot, but defaults to c=0 & u=0 (virDomainHostdevAssignAddress). There is some collision detection (virDomainDriveAddressIsUsedBy{Disk|Hostdev} and virDomainDefCheckDuplicateDriveAddresses), but the timing of when those checks can be called and when the above check is made is the issue. During parse virDomainHostdevAssignAddress is called if an address is not provided. That calls virDomainControllerSCSINextUnit to ensure no duplicate address is generated by checking both existing SCSI disk and hostdev's. If an address is provided, the virDomainHostdevDefPostParse can only check existing SCSI disks since virDomainHostdevInsert called during qemuDomainAttachDeviceConfig would have put that address on the hostdev list and calling virDomainSCSIDriveAddressIsUsed during post parse instead of just virDomainDriveAddressIsUsedByDisk would result in a conflict with itself. So prior to inserting into the list calling virDomainDefHasDeviceAddress (just like VIR_DOMAIN_DEVICE_RNG does in the same method) ensures the about to be added hostdev doesn't conflict with any existing hostdev because the parse code didn't make that check and checking for that conflict in post parse would cause And yes, if a duplicate was successfully inserted without the check, then startup would have a failure since the validate path would call virDomainDefCheckDuplicateDriveAddresses. If the "decision" is that we can allow the start to fail when someone provides duplicate addresses, then that's fine I can drop this patch. Although perhaps a comment in qemuDomainAttachDeviceConfig would help the next person (or even myself, because I'm sure to forget and see this again).
On the other hand, for hotplugged PCI devices ("LIVE"), both assigning addresses to devices with no supplied address, and checking for duplicate addresses is handled by qemuDomainEnsurePCIAddress (which calls virDomainPCIAddressEnsureAddr. No, I did not name either of them) - that is called directly from qemuDomainAttach${Blah}Device in qemu_hotplug.c.
So in both cases, nothing associated with *PCI* device addresses is done during the *Device* post parse callback, although in the case of CONFIG, addresses are assigned/checked by a "POST-postparse" manual call to the *Domain* PostParse callback.
Sigh. I was hoping to arrive at some nugget of good information that would point to the best solution. Instead I've just pointed out how convoluted everything is, and given myself more ideas of other possible bugs. Maybe if I look at it again in the morning with a fresh brain...
Address generation and checking just feels like one of those bolted onto the side type things when it was realized that we had to do something. PCI took one approach and SCSI a different approach. John
But no, I don't believe the same problem exists there. How would you suggest reproducing that?
If one virsh edit's their domain adding two hostdev's with the same <address>, then virDomainDefValidateInternal catches that with the call to virDomainDefCheckDuplicateDriveAddresses. With this patch if one calls attach-device --config with a duplicated <address>, then this check will catch that.
This is similar to VIR_DOMAIN_DEVICE_RNG processing in the same code.
John
Jano
if (virDomainHostdevInsert(vmdef, hostdev)) return -1; dev->data.hostdev = NULL; -- 2.14.4
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