On Fri, Jan 13, 2017 at 01:17:27PM +0000, Stefan Hajnoczi wrote: > On Fri, Jan 13, 2017 at 07:56:51PM +0800, Haozhong Zhang wrote: > > The missing of 'nvdimm' in the machine type option '-M' means NVDIMM > > is disabled. QEMU should refuse to plug any NVDIMM device in this case > > and report the misconfiguration. > > > > Reported-by: Stefan Hajnoczi <stefa...@redhat.com> > > Signed-off-by: Haozhong Zhang <haozhong.zh...@intel.com> > > Message-Id: 20170112110928.GF4621@stefanha-x1.localdomain > > Message-Id: 20170111093630.2088-1-stefa...@redhat.com > > --- > > hw/i386/pc.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > > index 25e8586..3907609 100644 > > --- a/hw/i386/pc.c > > +++ b/hw/i386/pc.c > > @@ -1715,6 +1715,11 @@ static void pc_dimm_plug(HotplugHandler *hotplug_dev, > > } > > > > if (object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM)) { > > + if (!pcms->acpi_nvdimm_state.is_enabled) { > > + error_setg(&local_err, > > + "nvdimm is not enabled: missing 'nvdimm' in '-M'"); > > + goto out; > > + } > > A warning is definitely useful to notify users of a possible > configuration error. > > I wonder what happens when you plug an NVDIMM into a motherboard where > the firmware lacks support. Does it: > * Refuse to boot? > * Treat the DIMM as regular RAM? > * Boot but the DIMM will not be used by firmware and kernel? > > QEMU should act the same way as real hardware.
If real hardware behavior is not useful in any way (e.g. first and third options above), is there a good reason for QEMU to not implement an additional safety mechanism preventing NVDIMM from being connected to a machine that doesn't support it? -- Eduardo