> On Mar 12, 2019, at 10:23 AM, David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 12.03.19 18:14, Matthew Wilcox wrote: >> 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: > > Just to clarify on that point, XEN balloon does not use balloon > compaction as far as I know (only virtio-balloon and as far as I know > now also vmware balloon). Both of them don't map any such pages to user > space, so it never was and isn't a problem. I still need to submit the next version of the patches, but yes, we are not about to map them to userspace (dah).
