On Wed, 11 Jun 2014 16:50:35 +1000 Alexey Kardashevskiy <a...@ozlabs.ru> wrote:
> On 06/11/2014 12:41 AM, Cornelia Huck wrote: > > On Tue, 10 Jun 2014 09:39:51 -0400 > > Luiz Capitulino <lcapitul...@redhat.com> wrote: > > > >> On Wed, 4 Jun 2014 18:08:47 +1000 > >> Alexey Kardashevskiy <a...@ozlabs.ru> wrote: > >> > >>> This introduces an NMI (non maskable interrupt) callback per CPU class > >>> which QMP's "nmi" command may use to issue NMI on a CPU. > >>> > >>> This adds support for it in qmp_inject_nmi(). Since no architecture > >>> supports it at the moment, there is no change in behaviour. > >>> > >>> This changes inject-nmi command description for HMP and QMP. > >>> > >>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> > >>> --- > >>> Changes: > >>> v3: > >>> * actual nmi() enablement moved from last patch to first patch > >>> * changed description for QMP command too > >>> --- > >>> cpus.c | 11 ++++++++++- > >>> hmp-commands.hx | 6 ++---- > >>> include/qom/cpu.h | 1 + > >>> qapi-schema.json | 4 +--- > >>> qmp-commands.hx | 3 +-- > >>> 5 files changed, 15 insertions(+), 10 deletions(-) > >>> > >>> diff --git a/qapi-schema.json b/qapi-schema.json > >>> index 7bc33ea..dcf6642 100644 > >>> --- a/qapi-schema.json > >>> +++ b/qapi-schema.json > >>> @@ -1748,13 +1748,11 @@ > >>> ## > >>> # @inject-nmi: > >>> # > >>> -# Injects an Non-Maskable Interrupt into all guest's VCPUs. > >>> +# Injects an Non-Maskable Interrupt into the given guest's VCPU. > >> > >> QMP doesn't have the concept of "current monitored CPU" you talk in the > >> intro email. In QMP you have to specify the CPU. You have to choices: > >> > >> - Add a new command that takes a CPU parameter (seems the best to me, as > >> people were asking for a different command anyways) > >> > >> - Add an optional parameter to inject-nmi. When the CPU parameter is > >> not specified, the command sends the NMI to all CPUs > > > > The s390 restart interrupt is a per-vcpu interrupt, which we really > > don't want to inject on _all_ vcpus. OTOH, we want to inject that > > interrupt on any vcpu - we don't care which one it is. So I'd really > > like an "inject nmi on default cpu" option. > > > Interesting thing. I was pushing "nmi" for ppc which did nmi only on the > current cpu but according to our architect Ben, I should inject NMI on all > CPUs because although XMON (inkernel debugger) tries to stop other CPUs, it > may fail to do that because of some interrupt deadlock. And - this is > important for us - this is what pHyp (native IBM hypervisor) does. > > Now I wonder how you are getting away with injecting NMI on one CPU only > and what will happen if we inject NMI on all? The Linux restart handler does stop the other cpus before doing any other work - see restart_int_handler in arch/s390/kernel/entry64.S and do_restart in arch/s390/kernel/ipl.c for the gory details ;) Other operating systems need to have something similar in place, as the restart interrupt is always directed to a single cpu (for example, z/VM has SYSTEM RESTART, which is always directed either to the default cpu or to a specified cpu).
