On 09.03.2020 09:48, Paul Durrant wrote: >> -----Original Message----- >> From: Jan Beulich <jbeul...@suse.com> >> Sent: 06 March 2020 17:17 >> To: Paul Durrant <xadimg...@gmail.com> >> Cc: sstabell...@kernel.org; jul...@xen.org; volodymyr_babc...@epam.com; >> w...@xen.org; >> konrad.w...@oracle.com; andrew.coop...@citrix.com; ian.jack...@eu.citrix.com; >> george.dun...@citrix.com; xen-devel@lists.xenproject.org; 'David Woodhouse' >> <dw...@infradead.org> >> Subject: Re: [PATCH 2/2] domain: use PGC_extra domheap page for shared_info >> >> On 06.03.2020 17:27, Paul Durrant wrote: >>>> -----Original Message----- >>>> From: Jan Beulich <jbeul...@suse.com> >>>> Sent: 06 March 2020 13:46 >>>> To: Paul Durrant <xadimg...@gmail.com> >>>> Cc: sstabell...@kernel.org; jul...@xen.org; volodymyr_babc...@epam.com; >>>> w...@xen.org; >>>> konrad.w...@oracle.com; andrew.coop...@citrix.com; >>>> ian.jack...@eu.citrix.com; >>>> george.dun...@citrix.com; xen-devel@lists.xenproject.org; 'David >>>> Woodhouse' <dw...@infradead.org> >>>> Subject: Re: [PATCH 2/2] domain: use PGC_extra domheap page for shared_info >>>> >>>> On 06.03.2020 14:41, Paul Durrant wrote: >>>>>> -----Original Message----- >>>>>> From: Jan Beulich <jbeul...@suse.com> >>>>>> Sent: 06 March 2020 13:36 >>>>>> To: Paul Durrant <xadimg...@gmail.com> >>>>>> Cc: sstabell...@kernel.org; jul...@xen.org; volodymyr_babc...@epam.com; >>>>>> w...@xen.org; >>>>>> konrad.w...@oracle.com; andrew.coop...@citrix.com; >>>>>> ian.jack...@eu.citrix.com; >>>>>> george.dun...@citrix.com; xen-devel@lists.xenproject.org; 'David >>>>>> Woodhouse' <dw...@infradead.org> >>>>>> Subject: Re: [PATCH 2/2] domain: use PGC_extra domheap page for >>>>>> shared_info >>>>>> >>>>>> On 06.03.2020 14:26, Paul Durrant wrote: >>>>>>>> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of >>>>>>>> Jan Beulich >>>>>>>> Sent: 06 March 2020 13:24 >>>>>>>> >>>>>>>> On 06.03.2020 14:13, Paul Durrant wrote: >>>>>>>>> My aim is to make the separation abundantly obvious by getting rid >>>>>>>>> of shared xenheap pages (for non-system domains at least) but I >>>>>>>>> can't do that before converting shared_info and grant shared/status >>>>>>>>> frames to domheap. >>>>>>>> >>>>>>>> Following David's various replies - instead of going this route of >>>>>>>> replacing the sharing of xenheap pages by different logic, the >>>>>>>> same ought to be achievable by making the backing allocations come >>>>>>>> from the correct pool? >>>>>>>> >>>>>>> >>>>>>> I still prefer the simplification of not having to clean up the >>>>>>> shared xenheap page list in domain_kill() so IMO it is still worth >>>>>>> it for that alone. >>>>>> >>>>>> I don't see anything very special with the cleaning up in >>>>>> domain_kill() / domain_relinquish_resources(). What I'd view as >>>>>> more desirable in this regard is the general fact of needing >>>>>> two lists. But you realize there's a downside to this as well? >>>>>> dump_pageframe_info() will reliably show _all_ Xen heap pages >>>>>> associated with a domain, but it will only ever show up to 10 >>>>>> pages on ->page_list for a domain that's not already being >>>>>> cleaned up. >>>>> >>>>> That's not much of a downside though I don't think. The xenheap >>>>> (or PGC_extra domheap pages) are 'special' and so info about >>>>> them ought to be available via an alternate dump function anyway >>>>> (and if not already, it can be added). >>>> >>>> Whatever you'd add, the logic would need to either traverse the >>>> entire ->page_list (can take very long) or have/use out of band >>>> information where such pages may have a record (fragile). >>>> >>> >>> But the shared xenheap pages in question are only shared info, or >>> grant table, so their information can be dumped separately. >>> I guess it makes more sense to add another patch into the series >>> to do explicit dump of shared_info and then exclude 'special' >>> pages from dump_pageframe_info(). >> >> Bu that's why I said "fragile" - new uses of such pages wouldn't >> automatically be picked up, whereas them all landing on xenpage_list >> made their dumping a reliable thing. >> > > But how useful is dumping xenheap pages this way? There's nothing > that actually says what they are for so I can't see why it is > particularly useful.
That's no different from the domheap page list dumping. The main point of it - aiui - is to have a hook on finding where possible leaks sit. For xenheap pages, actually, one can (currently) infer what they are used for from their position on the list, I think. > Having something that says 'This is the shared_info page' and > 'These are the grant shared frames' seems much more desirable... > and any new ones added would almost certainly merit similar dump > functions. Possibly, yet that's different (partly extended, partly orthogonal) functionality. Doing such may indeed be useful. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
