[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] xen: Can't insert balloon page into VM userspace (WAS Re: [linux-linus bisection] complete test-arm64-arm64-xl-xsm)
On Tue, Mar 12, 2019 at 05:05:39PM +0000, Julien Grall wrote: > On 3/12/19 3:59 PM, Julien Grall wrote: > > It looks like all the arm test for linus [1] and next [2] tree > > are now failing. x86 seems to be mostly ok. > > > > The bisector fingered the following commit: > > > > commit 0ee930e6cafa048c1925893d0ca89918b2814f2c > > Author: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Date: Tue Mar 5 15:46:06 2019 -0800 > > > > mm/memory.c: prevent mapping typed pages to userspace > > Pages which use page_type must never be mapped to userspace as it would > > destroy their page type. Add an explicit check for this instead of > > assuming that kernel drivers always get this right. Oh good, it found a real problem. > It turns out the problem is because the balloon driver will call > __SetPageOffline() on allocated page. Therefore the page has a type and > vm_insert_pages will deny the insertion. > > My knowledge is quite limited in this area. So I am not sure how we can > solve the problem. > > I would appreciate if someone could provide input of to fix the mapping. I don't know the balloon driver, so I don't know why it was doing this, but what it was doing was Wrong and has been since 2014 with: commit d6d86c0a7f8ddc5b38cf089222cb1d9540762dc2 Author: Konstantin Khlebnikov <k.khlebnikov@xxxxxxxxxxx> Date: Thu Oct 9 15:29:27 2014 -0700 mm/balloon_compaction: redesign ballooned pages management If ballooned pages are supposed to be mapped into userspace, you can't mark them as ballooned pages using the mapcount field. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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