> On Apr 11, 2017, at 4:10 PM, Boris Ostrovsky <boris.ostrov...@oracle.com> > wrote: > > > >>> >>> I think the right thing is indeed to revert 72a9b186292 (and >>> therefore da72ff5bfcb02). Any objections? >> >> For the end result: depends. Is there a real error or not? >> KarimAllah wrote that his concerns are of a theoretical nature as >> xen_strict_xenbus_quirk() would mask the problem. OTOH he tells us >> a 4.9 kernel wouldn't even boot on Xen < 4.0. What is correct here? > > > Judged by 'BUG_ON(!xen_feature(XENFEAT_hvm_callback_vector))' in > xen_hvm_guest_init() this can't boot on 3.4.
Correct. Here is the brief summary of the current situation: Before the offending commit (72a9b186292): 1) INTx does not work because of the reset_watches path. 2) The reset_watches path is only taken if you have Xen > 4.0 3) The Linux Kernel by default will use vector inject if the hypervisor support. So even INTx does not work no body running the kernel with Xen > 4.0 would notice. Unless he explicitly disabled this feature either in the kernel or in Xen (and this can only be disabled by modifying the code, not user-supported way to do it). After the offending commit (+ partial revert): 1) INTx is no longer support for HVM (only for PV guests). 2) Any HVM guest The kernel will not boot on Xen < 4.0 which does not have vector injection support. Since the only other mode supported is INTx which. So based on this summary, I think before commit (72a9b186292) we were in much better position from a user point of view. > > >> >> For just reverting the two commits: yes, as there would be conflicts >> with already applied patches, especially the pv isolation patches by >> Vitaly and pvh v1 removal. >> >> So in case we need a revert I'd ask KarimAllah to send a fixup patch >> restoring the state before 72a9b186292 while respecting the new >> structure to be found on the for-linus-4.12 branch of xen/tip. > > Stable trees (4.9 and 4.10) need a pure revert. 4.11 indeed requires some > extra work (and 4.12 is even more involved). If we agreed on going forward with the revert, I will take care of sending the patches to revert for various trees. > > -boris > Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
