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Re: [Qemu-devel] [PATCH] hw/i386: check if nvdimm is enabled before plug
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH] hw/i386: check if nvdimm is enabled before plugging |
Date: |
Fri, 13 Jan 2017 16:02:43 -0200 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
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 <address@hidden>
> > Signed-off-by: Haozhong Zhang <address@hidden>
> > Message-Id: address@hidden
> > Message-Id: address@hidden
> > ---
> > 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
Re: [Qemu-devel] [PATCH] hw/i386: check if nvdimm is enabled before plugging, Stefan Hajnoczi, 2017/01/23