[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/balloon: set ballooned out pages as invalid in p2m
On Tue, Jul 01, 2014 at 03:00:16PM +0100, David Vrabel wrote: > On 01/07/14 14:58, Konrad Rzeszutek Wilk wrote: > > On Tue, Jul 01, 2014 at 02:37:48PM +0100, David Vrabel wrote: > >> Since cd9151e26d31048b2b5e00fd02e110e07d2200c9 (xen/balloon: set a > >> mapping for ballooned out pages), a ballooned out page had its entry > >> in the p2m set to the MFN of one of the scratch pages. This means > >> that the p2m will contain many entries pointing to the same MFN. > >> > >> During a domain save, these many-to-one entries are not identified as > >> such and the scratch page is saved multiple times. On restore the > >> ballooned pages are populated with new frames and the domain may use > >> up its allocation before all pages can be restored. > >> > >> Set ballooned out pages as INVALID_P2M_ENTRY in the p2m (as they were > >> before), preventing them from being saved and re-populated on restore. > >> > > > > Won't that invalide the primal purpose of the scratch page code? > > > > That is cd9151e26d31048b2b5e00fd02e110e07d2200c9 > > > > xen/balloon: set a mapping for ballooned out pages > > " Allocate a page per cpu and map all the ballooned out pages to the > > corresponding mfn. Set the p2m accordingly. This way reading from a > > ballooned out page won't cause a kernel crash (see > > http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html). > > " > > ? > > No, because we still have a virtual mapping for the ballooned out page. If you could add that comment in that would reflect that - IMHO it would be good. > > David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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