Woller, Thomas
2008-Jan-15 19:22 UTC
[Xen-devel] [PATCH][P2M] add printk to NP PAE logic in p2m
Adding a P2M_ERROR message when startup of a PAE HVM guest, on a PAE hypervisor exceeds the ~4Gig memory size limitation. Please apply to unstable (no need to add to 3.2-testing, or to 3.1.3). Signed-off-by: Tom Woller <thomas.woller@amd.com> --Tom thomas.woller@amd.com +1-512-602-0059 AMD Corporation - Operating Systems Research Center Austin, Texas _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2008-Jan-15 19:31 UTC
Re: [Xen-devel] [PATCH][P2M] add printk to NP PAE logic in p2m
If we add that printk() then it''s on a path triggerable by an HVM guest (via the populate_physmap hypercall, for example) and there is a potential DoS attack. The need to modify the Xen command line to enable NPT on PAE hypervisor should really be caveat enough anyway. -- Keir On 15/1/08 19:22, "Woller, Thomas" <thomas.woller@amd.com> wrote:> Adding a P2M_ERROR message when startup of a PAE HVM guest, on a PAE > hypervisor exceeds the ~4Gig memory size limitation. > > Please apply to unstable (no need to add to 3.2-testing, or to 3.1.3). > > Signed-off-by: Tom Woller <thomas.woller@amd.com> > > --Tom > > thomas.woller@amd.com +1-512-602-0059 > AMD Corporation - Operating Systems Research Center > Austin, Texas > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Stephen C. Tweedie
2008-Jan-16 15:36 UTC
Re: [Xen-devel] [PATCH][P2M] add printk to NP PAE logic in p2m
Hi, On Tue, 2008-01-15 at 19:31 +0000, Keir Fraser wrote:> If we add that printk() then it''s on a path triggerable by an HVM guest (via > the populate_physmap hypercall, for example) and there is a potential DoS > attack. The need to modify the Xen command line to enable NPT on PAE > hypervisor should really be caveat enough anyway.Hardly, there''s no reason at all for a user to assume that enabling NPT in that situation will cause guest address spaces to be truncated. Ideally we''d have a text message delivered back to the user on all domain creations when this truncation happens. A log message is probably the minimum reasonable notification; truncating silently is a pretty poor option. There are plenty of solutions --- simply do the printk once per domain, for example, or rate-limit it, or don''t do it when the physmap is populated but have a separate test at domain build time. But truncating silently seems to be one of the worst alternatives. Cheers, Stephen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Stephen C. Tweedie
2008-Jan-16 16:52 UTC
Re: [Xen-devel] [PATCH][P2M] add printk to NP PAE logic in p2m
Hi, On Tue, 2008-01-15 at 19:31 +0000, Keir Fraser wrote:> If we add that printk() then it''s on a path triggerable by an HVM guest (via > the populate_physmap hypercall, for example) and there is a potential DoS > attack. The need to modify the Xen command line to enable NPT on PAE > hypervisor should really be caveat enough anyway.Hardly, there''s no reason at all for a user to assume that enabling NPT in that situation will cause guest address spaces to be truncated. Ideally we''d have a text message delivered back to the user on all domain creations when this truncation happens. A log message is probably the minimum reasonable notification; truncating silently is a pretty poor option. There are plenty of solutions --- simply do the printk once per domain, for example, or rate-limit it, or don''t do it when the physmap is populated but have a separate test at domain build time. But truncating silently seems to be one of the worst alternatives. Cheers, Stephen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
hi I have read something about netchannel2 somewhere ,say xen-summit or somewhere else, and i am interested in the netchannel2,but with some confusion ,and has netchannel2 been integrated and supported by xen or not ? and could anyone give me a detailed explanation about the mechanism and implementation of netchannel2 and its status Thanks in advance _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
>hi > I have read something about netchannel2 somewhere ,say xen-summit or >somewhere else, and i am interested in the netchannel2,but with some >confusion ,and has netchannel2 been integrated and supported >by xen or not ?no yet.> and could anyone give me a detailed explanation about the >mechanism and implementation of netchannel2 and its statuswhat''s your confusion? -Xin _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
hi thank you for your reply, and I have read something about netchannel2,and then ,nowadays , i read the summit ppt which refer to the integration of the netchannel2, but, to be frank, i forget the main idea of netchannel2 ,only remembering that it is interesting and about something to improve the network performance or something about smartNIC,which i am not clear about either,and i could not find the paper or doc about them , and could you give me some explanation about it ,or give me some paper about it or some guide about netchannel2''s motivation and main idea or something Thanks in advance Li, Xin B 写道:>> hi >> I have read something about netchannel2 somewhere ,say xen-summit or >> somewhere else, and i am interested in the netchannel2,but with some >> confusion ,and has netchannel2 been integrated and supported >> by xen or not ? >> > > no yet. > > >> and could anyone give me a detailed explanation about the >> mechanism and implementation of netchannel2 and its status >> > > what''s your confusion? > -Xin > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel