On Mon, 1 Aug 2016 15:47:58 +0200 "Jan Beulich" <jbeul...@suse.com> wrote:
> (re-adding xen-devel) > > >>> On 01.08.16 at 15:02, <ptesa...@suse.com> wrote: > > On Mon, 1 Aug 2016 13:55:01 +0200 > > "Jan Beulich" <jbeul...@suse.com> wrote: > > > >> >>> On 13.07.16 at 14:53, <david.vra...@citrix.com> wrote: > >> > On 13/07/16 13:20, Petr Tesarik wrote: > >> >> If a crash kernel is loaded, do not crash the running domain. This is > >> >> needed if the kernel is loaded with crash_kexec_post_notifiers, because > >> >> panic notifiers are run before __crash_kexec() in that case, and this > >> >> Xen hook prevents its being called later. > >> > > >> > Prioritising the in-kernel kexec image over the hypervisor one seems > >> > sensible behaviour to me. > >> > >> For HVM guests certainly; does loading of an in-kernel crash kernel > >> properly fail for PV guests (and namely PV Dom0), or does such a > >> setup work nowadays? > > > > This is a good question, but I don't think it is relevant to this > > patch. It does not change anything unless the kernel is booted with > > crash_kexec_post_notifiers. > > > > I fully understand that Dom0 kernels want to load the panic kernel in > > the hypervisor and crash the complete machine, rather than just Dom0, > > but if you want that behaviour, simply pass the "crashkernel=" > > parameter only to the Xen hypervisor and not to the Dom0 kernel. > > > > Did I miss something? > > For one there are still many people who, for varying reasons, add > "crashkernel=" also to Dom0's command line. Is there a valid use case for it? FWIW the legacy Xen implementation (as found in SLES) simply ignores the 'crashkernel=' kernel parameter. The code is not even compiled in. > And then trying to invoke a locally loaded crash kernel which won't > work is bad Without actually knowing whether a PV kernel can kexec another PV kernel, this discussion is somewhat moot... But let me repeat: if PV kexec works, then it has always had priority over the hypercall. If it doesn't work, then it has always been broken. For the latter case, I agree that the kernel should not even allow to load the kexec image, but that's unrelated to my patch. Has anyone here tried booting up a PV domain and performing kexec(2)? I can't test it with my SLES12 installation, because the kexec(8) user-space utility is patched in SLES to load the hypervisor kexec image with a hypercall if Xen is detected. Petr T _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
