On Mon, 2011-02-21 at 16:40 +0000, Alan Stern wrote: > On Mon, 21 Feb 2011, Ian Campbell wrote: > > > On Sun, 2011-02-20 at 07:49 +0000, Pavel Machek wrote: > > > On Sat 2011-02-19 15:12:35, Shriram Rajagopalan wrote: > > > > The current implementation of xen guest save/restore/checkpoint functionality > > > > uses PM_SUSPEND and PM_RESUME events. This is not optimal when taking > > > > checkpoints of a virtual machine (where the suspend hypercall returns > > > > non-zero, requiring the devices and xenbus to just pickup from where they left > > > > off instead of a complete teardown/reconnect to backend). > > > > > > > > The following set of patches modify this implementation to use Hibernate style > > > > control flow (freeze/restore for save/restore and freeze/thaw for checkpoint, > > > > which is merely a cancelled save akin to failed swsusp() ). > > > > > > > > These patches are against Ian Campbell's PVHVM tree at > > > > git://xenbits.xen.org/people/ianc/linux-2.6.git for-stefano/pvhvm > > > > > > > > at commit 8a8d1bc753c4e2dda5f2890292d60c67d6ebb573 > > > > kernel version: 2.6.38-rc4 > > > > > > Series looks ok to me... > > > > Thanks Pavel, may we take that as an Acked-by? > > > > For my part the Xen side is: > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx> > > There's one part of this which could be troublesome. The new code > generates FREEZE, THAW, and RESTORE events even in kernels where > CONFIG_HIBERNATION isn't set. In such kernels, drivers are not > obliged to handle these events correctly. The dependencies on CONFIG_HIBERNATION which I can see appear to be more often at the bus level (e.g. in drivers/acpi drivers/pci/pci-driver.c etc) is that right? For a PV guest only the Xen PV drivers really matter. But for a PVHVM guest you are right since there are the emulated "PC" devices though which could be problematic. There's nothing especially thrilling in that set of devices although I don't think that invalidates your point. > Shouldn't the CONFIG_XEN_SAVE_RESTORE option select CONFIG_HIBERNATION? > In which case the #ifdef lines in pm_op() wouldn't need to be changed. I think selecting user-visible symbols is generally frowned upon. But apart from that I was concerned that tying the Xen functionality into the hibernation option was a bit odd/artificial. Perhaps it's the only solution though. Ian. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
