[libvirt] [PATCH v2 03/14] qemu_hotplug: pull qemuDomainUpdateDeviceList out of qemuDomainDetachDeviceLive

[Peter Krempa]

On Mon, Mar 25, 2019 at 13:24:25 -0400, Laine Stump wrote:
> qemuDomainDetachDeviceLive() is called from two places in
> qemu_driver.c, and qemuDomainUpdateDeviceList() is called from the
> end of qemuDomainDetachDeviceLive(), which is now in qemu_hotplug.c
> 
> This patch replaces the single call to qemuDomainUpdateDeviceList()
> with two calls to it immediately after return from
> qemuDomainDetachDeviceLive(). This is only done if the return from
> that function is exactly 0, in order to exactly preserve previous
> behavior.
> 
> Removing that one call from qemuDomainDetachDeviceList() will permit
> us to call it from the test driver hotplug test, replacing the
> separate calls to qemuDomainDetachDeviceDiskLive(),
> qemuDomainDetachChrDevice(), qemuDomainDetachShmemDevice() and
> qemuDomainDetachWatchdog(). We want to do this so that part of the
> common functionality of those three functions (and the rest of the
> device-specific Detach functions) can be pulled up into
> qemuDomainDetachDeviceLive() without breaking the test. (This is done
> in the next patch).
> 
> NB: Almost certainly this is "not the best place" to call
> qemuDomainUpdateDeviceList() (actually, it is provably the *wrong*
> place), since it's purpose is to retrieve an "up to date" list of
> aliases for all devices from qemu, and if the guest OS hasn't yet
> processed the detach request, the now-being-removed device may still
> be on that list. It would arguably be better to instead call
> qemuDomainUpdateDevicesList() later during the response to the
> DEVICE_DELETED event for the device. But removing the call from the
> current point in the detach could have some unforeseen ill effect due
> to changed timing, so the change to move it into
> qemuDomainRemove*Device() will be done in a separate patch (in order
> to make it easily revertible in case it causes a regression).

Actually it probably would cause a regression. It's called only when the
device is removed. That function will require some overhauling.

> 
> Signed-off-by: Laine Stump <laine at laine.org>
> ---
> 
> Change from V1:
> 
> * Added the big explanation above about why I'm not completely
>   changing behavior by waiting unt after DEVICE_DELETED to call
>   qemuDomainUpdateDeviceList()
> 
> * Only call qemuDomainUpdateDeviceList() if the Detach function
>   returned *exactly* 0, since there are cases where it could return >
>   0, and the previous behavior was to not call it in those cases.

ACK
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