On Fri, 2 Sep 2011 12:39:19 +0100 David Vrabel <david.vrabel@xxxxxxxxxx> wrote: > Xen backend drivers (e.g., blkback and netback) would sometimes fail > to map grant pages into the vmalloc address space allocated with > alloc_vm_area(). The GNTTABOP_map_grant_ref would fail because Xen > could not find the page (in the L2 table) containing the PTEs it > needed to update. > > (XEN) mm.c:3846:d0 Could not find L1 PTE for address fbb42000 > > netback and blkback were making the hypercall from a kernel thread > where task->active_mm != &init_mm and alloc_vm_area() was only > updating the page tables for init_mm. The usual method of deferring > the update to the page tables of other processes (i.e., after taking a > fault) doesn't work as a fault cannot occur during the hypercall. > > This would work on some systems depending on what else was using > vmalloc. > > Fix this by reverting ef691947d8a3d479e67652312783aedcf629320a > (vmalloc: remove vmalloc_sync_all() from alloc_vm_area()) and add a > comment to explain why it's needed. oookay, I queued this for 3.1 and tagged it for a 3.0.x backport. I *think* that's the outcome of this discussion, for the short-term? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>