[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] yanked share, round 2
Hi Anthony -- Can you explain why this is ideal? I prefer that sharers and mappers have their own skin the game--that way, Xen doesn't have to manage a pool and nobody has to worry about the pool being depleted. -----Original Message----- From: Anthony Liguori [mailto:aliguori@xxxxxxxxxx] Sent: Friday, January 13, 2006 11:23 AM To: King, Steven R Cc: xen-devel@xxxxxxxxxxxxxxxxxxx Subject: Re: [Xen-devel] yanked share, round 2 An ideal solution to this problem would be to keep a separate pool of shared memory that neither domain owned. That removes any concerns about ownership. Regards, Anthony Liguori King, Steven R wrote: > Hi folks, > A previous thread discussed complications around DomU's sharing memory > pages with each other: > http://lists.xensource.com/archives/html/xen-devel/2005-12/msg00499.ht > ml > > To summarize, DomU's get into trouble, e.g. unable to shutdown, unless > the remote DomU's play nice. Since DomU's do not trust each other, > that is problematic. I'd like to discuss how to clean away this > dependency. > > Here's one idea. The goal is to robustly decouple the sharing and > remote domains. > > Grant tables add a new GTF_safe flag, settable by the sharing DomU. > In order to map a GTF_safe page, a remote domain must provide a page > of its own, which I'll call an "under page". > Xen holds the under-page on behalf of the remote DomU and maps the > shared page into the remote DomU's machine. > At any time, the sharing DomU can unshare the page, crash, etc, which > ends ALL foreign access to that page, not just new mappings. > For each remote domain that still maps the unshared page, Xen maps the > remote's under-page in place of the unshared page. > The remote domain can unmap at any time and recover its under-page. > > The purpose of the under-page is to plug the memory hole in the remote > DomU created by a surprise unsharing. A nervous remote DomU could > check that a share is GTF_safe before proceeding to map the page. > > Good, bad or ugly? > -steve > > > > >----------------------------------------------------------------------- >- > >_______________________________________________ >Xen-devel mailing list >Xen-devel@xxxxxxxxxxxxxxxxxxx >http://lists.xensource.com/xen-devel > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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