Re: [libvirt] [PATCH v2 1/9] hostdev: Add virHostdevOnlyReattachPCIDevice()

  w/r/t: your [0/7] from initial series...   As much as you don't want to keep living Groundhog Day - resolution of bugs like this are job security :-)...

w/r/t Suggestions for deamon restart issues... Seems like we need a way to save/restore the hostdev_mgr active/inactive lists using XML/JSON similar to how domains, storage, etc. handle it. Guess I just assumed that was already there ;-) since /var/run/libvirt/hostdevmgr exists. It seems that network stuff can be restored - virHostdevNetConfigRestore.   Do you really think this series should be "held up" waiting to create some sort of status tracking?

On 01/25/2016 11:20 AM, Andrea Bolognani wrote: > This function replaces virHostdevReattachPCIDevice() and, unlike it, > does not perform list manipulation, leaving it to the calling function. >  > This means virHostdevReAttachPCIDevices() had to be updated to cope > with the updated requirements. > --- >  src/util/virhostdev.c | 136 +++++++++++++++++++++++++++++++++----------------- >  1 file changed, 90 insertions(+), 46 deletions(-)   Since I reviewed them all... I think the comment changes from 7/9 should just be inlined here and patch 4 instead of a separate patch

> diff --git a/src/util/virhostdev.c b/src/util/virhostdev.c > index f31ad41..66629b4 100644 > --- a/src/util/virhostdev.c > +++ b/src/util/virhostdev.c > @@ -526,6 +526,74 @@ virHostdevNetConfigRestore(virDomainHostdevDefPtr hostdev, >      return ret; >  } >   > +/** > + * virHostdevOnlyReattachPCIDevice:   Why not just reuse the function name you deleted? IOW: Is there a reason for "Only"? (not that I'm one that can complain about naming functions, but this just seems strange).

> + * @mgr: hostdev manager > + * @pci: PCI device to be reattached   Interesting ... In 2 instances, this will be a pointer to the "copy" element, while in the third instance this will be the "actual" on inactive list element.  For a copy element, we'd *have* to search inactive; however, for an 'actual' we don't "need" to.

> + * @skipUnmanaged: whether to skip unmanaged devices > + * > + * Reattach a PCI device to the host. > + * > + * This function only performs the base reattach steps that are required > + * regardless of whether the device is being detached from a domain or > + * had been simply detached from the host earlier. > + * > + * @pci must have already been marked as inactive, and the PCI related > + * parts of @mgr (inactivePCIHostdevs, activePCIHostdevs) must have been > + * locked beforehand using virObjectLock(). > + * > + * Returns: 0 on success, <0 on failure > + */ > +static int > +virHostdevOnlyReattachPCIDevice(virHostdevManagerPtr mgr, > +                                virPCIDevicePtr pci, > +                                bool skipUnmanaged) > +{ > +    virPCIDevicePtr actual; > +    int ret = -1; > + > +    /* Retrieve the actual device from the inactive list */ > +    if (!(actual = virPCIDeviceListFind(mgr->inactivePCIHostdevs, pci))) { > +        VIR_DEBUG("PCI device %s is not marked as inactive", > +                  virPCIDeviceGetName(pci));   This is tricky - the only time we care about the return status (now) is when skipUnmanaged == false, a/k/a the path where we pass the onlist element..   In my first pass through the changes I thought - oh no if we return -1, then this would be a path that could get that generic libvirt failed for some reason message; however, closer inspection noted that we guaranteed it was on the inactive list before calling here.

> +        goto out; > +    } > + > +    /* Skip unmanaged devices if asked to do so */ > +    if (!virPCIDeviceGetManaged(actual) && skipUnmanaged) {   <sigh>, unrelated and existing - virPCIDeviceGetManaged probably should return bool instead of unsigned int

> +        VIR_DEBUG("Not reattaching unmanaged PCI device %s", > +                  virPCIDeviceGetName(actual)); > +        ret = 0; > +        goto out; > +    } > + > +    /* Wait for device cleanup if it is qemu/kvm */ > +    if (virPCIDeviceGetStubDriver(actual) == VIR_PCI_STUB_DRIVER_KVM) { > +        int retries = 100; > +        while (virPCIDeviceWaitForCleanup(actual, "kvm_assigned_device") > +               && retries) { > +            usleep(100*1000); > +            retries--; > +        } > +    }   Existing, but if retries == 0, then cleanup never succeeded; however, perhaps one can assume that the subsequent call would fall over and play dead? Not that it really gets checked...

> + > +    VIR_DEBUG("Reattaching PCI device %s", virPCIDeviceGetName(actual)); > +    if (virPCIDeviceReattach(actual, mgr->activePCIHostdevs, > +                             mgr->inactivePCIHostdevs) < 0) { > +        virErrorPtr err = virGetLastError(); > +        VIR_ERROR(_("Failed to reattach PCI device %s: %s"), > +                  virPCIDeviceGetName(actual), > +                  err ? err->message : _("unknown error")); > +        virResetError(err); > +        goto out; > +    } > + > +    ret = 0; > + > + out: > +    return ret; > +} > + >  int >  virHostdevPreparePCIDevices(virHostdevManagerPtr hostdev_mgr, >                              const char *drv_name, > @@ -753,45 +821,6 @@ virHostdevPreparePCIDevices(virHostdevManagerPtr hostdev_mgr, >      return ret; >  } >   > -/* > - * Pre-condition: inactivePCIHostdevs & activePCIHostdevs > - * are locked > - */ > -static void > -virHostdevReattachPCIDevice(virPCIDevicePtr dev, virHostdevManagerPtr mgr) > -{ > -    /* If the device is not managed and was attached to guest > -     * successfully, it must have been inactive. > -     */ > -    if (!virPCIDeviceGetManaged(dev)) { > -        VIR_DEBUG("Adding unmanaged PCI device %s to inactive list", > -                  virPCIDeviceGetName(dev)); > -        if (virPCIDeviceListAdd(mgr->inactivePCIHostdevs, dev) < 0) > -            virPCIDeviceFree(dev); > -        return; > -    } > - > -    /* Wait for device cleanup if it is qemu/kvm */ > -    if (virPCIDeviceGetStubDriver(dev) == VIR_PCI_STUB_DRIVER_KVM) { > -        int retries = 100; > -        while (virPCIDeviceWaitForCleanup(dev, "kvm_assigned_device") > -               && retries) { > -            usleep(100*1000); > -            retries--; > -        } > -    } > - > -    VIR_DEBUG("Reattaching PCI device %s", virPCIDeviceGetName(dev)); > -    if (virPCIDeviceReattach(dev, mgr->activePCIHostdevs, > -                             mgr->inactivePCIHostdevs) < 0) { > -        virErrorPtr err = virGetLastError(); > -        VIR_ERROR(_("Failed to re-attach PCI device: %s"), > -                  err ? err->message : _("unknown error")); > -        virResetError(err); > -    } > -    virPCIDeviceFree(dev); > -} > - >  /* @oldStateDir: >   * For upgrade purpose: see virHostdevNetConfigRestore >   */ > @@ -803,7 +832,7 @@ virHostdevReAttachPCIDevices(virHostdevManagerPtr hostdev_mgr, >                               int nhostdevs, >                               const char *oldStateDir) >  { > -    virPCIDeviceListPtr pcidevs; > +    virPCIDeviceListPtr pcidevs = NULL; >      size_t i; >   >      if (!nhostdevs) > @@ -848,11 +877,25 @@ virHostdevReAttachPCIDevices(virHostdevManagerPtr hostdev_mgr, >                      continue; >                  } >          } > +        i++; > +    }   Curious why the decision for a second loop - if activeDev matches, then it almost seems a shame to loop again. Why not (within if (activeDev):        actual = virPCIDeviceListSteal(hostdev_mgr->activePCIHostdevs,                                     activeDev);      /* !actual should never happen, but better safe than sorry */      if (actual &&          virPCIDeviceListAdd(hostdev_mgr->inactivePCIHostdevs,                              actual) < 0)              virPCIDeviceFree(actual);              /* You could also... */              virPCIDeviceListDel(pcidevs, dev);      }

NOTE: Whether there is one or two loops, the second loop would need to call virPCIDeviceFree(actual) since we'd leak it otherwise.

You'll also note I didn't keep the goto cleanup. Previously the code would completely go through the pcidevs Loop 4 regardless of whether virHostdevReattachPCIDevice code had failures. The new code has the subtle difference of jumping to cleanup if a failure is found. That could leave things in an awkward state especially since virHostdevReAttachPCIDevices is a void.   Since failure for DeviceListAdd is because 1. device is already there (which I would *hope* isn't the case) or 2. memory allocation failure (in which case not much else successful will probably happen anyway), then perhaps continuing on rather than jumping to cleanup isn't a bad idea... We could be returning some memory that someone may find useful.   My concerns about jumping to cleanup are that this API is called in error recovery paths as well as part of the ominous comment "For upgrade purpose:..." (comment before function header). So it seems the "existing logic" is try to clean up as many as possible. By potentially erroring out too soon could lead to more problems.   So the question becomes what havoc is introduced if we cannot add to the inactive list but decide to continue as before... It seems we'll end up "failing" in virHostdevOnlyReattachPCIDevice since it's not in the inactiveList, but our Loop 4 logic doesn't care. Of course we could delete 'dev' from 'pcidevs' too before then...   Hopefully this makes sense... It's been an 'edit in process'...

> + > +    /* Step 2: move all devices from the active list to the inactive list */ > +    for (i = 0; i < virPCIDeviceListCount(pcidevs); i++) { > +        virPCIDevicePtr dev = virPCIDeviceListGet(pcidevs, i); > +        virPCIDevicePtr actual; >   >          VIR_DEBUG("Removing PCI device %s from active list", >                    virPCIDeviceGetName(dev)); > -        virPCIDeviceListDel(hostdev_mgr->activePCIHostdevs, dev);   This was a curious placement for *ListDel... If !activeDev, then calling *ListDel also won't find 'dev' on activelist...

> -        i++; > +        if (!(actual = virPCIDeviceListSteal(hostdev_mgr->activePCIHostdevs, > +                                             dev))) > +            goto cleanup;   If the choice is to use two loops (and perhaps keep the cleanups)...   1. If this Steal fails, then something is seriously wrong, but we don't even give it a VIR_DEBUG message.   2. If this Steal fails, then going to cleanup is again a subtle difference with the prior logic that said, well I couldn't do anything with this, but I'm going to keep processing.   3. If we keep processing, then something on 'pcidevs' won't be in 'inactivePCIHostdevs', causing virHostdevOnlyReattachPCIDevice to fail. But that does not matter since we ignore the return value in Loop 4.   4. If we do Steal and if the subsequent Add fails, then we leak 'actual', so prior to the goto cleanup call virPCIDeviceFree(actual); (or instead if the goto cleanup;'s are removed).