We can trigger NMI from HMP or QMP.
QEMU maps the NMI to the s390x per-CPU 'RESTART' interrupt.
Linux guests usually setup this interrupt to trigger kdump
or crash. Such crashdump can be triggered in QEMU by HMP
"nmi" or QMP "inject-nmi" commands.
Using QMP, since we can not select a particular CPU, the first
CPU is used (CPU#0). See the documentation from commit 795dc6e4
("watchdog: Add new Virtual Watchdog action INJECT-NMI"):
@inject-nmi: a non-maskable interrupt is injected into the
first VCPU (all VCPUS on x86) (since 2.4)
While we can select a particular CPU on HMP, the guest behavior
is expected to be the same if using CPU #N or CPU #0. Since
always using CPU#0 simplifies API maintainance, update s390_nmi()
to deliver NMI to the first CPU.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
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