|From:||Jeremy Fitzhardinge <firstname.lastname@example.org>|
|To:||Ingo Molnar <email@example.com>|
|Subject:||[PATCH 00 of 12] xen: add save/restore/migrate for Xen domains|
|Date:||Fri, 23 May 2008 14:41:07 +0100|
|Cc:||LKML <firstname.lastname@example.org>, xen-devel <email@example.com>, Thomas Gleixner <firstname.lastname@example.org>, "Rafael J. Wysocki" <email@example.com>|
Hi Ingo, This series adds save/restore/migrate for Xen domains. This is almost entirely contained within the Xen-specific code. The only exception is the WARN_ON I remove in hres_timers_resume, which is spurious in the case of a Xen suspend/resume, since we don't offline all the CPUs. This also adds another user of the freezer, since it turns out to solve a somewhat tricky problem. The problem is that Xen pagetables are expressed in terms of machine frame numbers - ie, the page numbers of the underlying host machine. When the domain is saved, all the mfns everywhere are canonicalized into guest-relative pfns in the save image. The tricky part is that when preemption is enabled, it's possible the suspend will preempt a pagetable manipulation, which will leave a machine frame number sitting in a register or on the stack which will not be canonicalized. The freezer solves this because it makes sure that every thread is quiesced at a well known point, which is not during a pagetable update. So by freezing everything and then stopping all the processors in stop_machine, we can make sure the system is in a saveable state. The freezer is only required when preemption is enabled, since stop_machine will quiesce all processors (and therefore threads) at suitable points anyway. J
Copyright © 2008, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds