From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41799) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cS6Bl-000253-6a for qemu-devel@nongnu.org; Fri, 13 Jan 2017 13:03:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cS6Bb-00031j-8a for qemu-devel@nongnu.org; Fri, 13 Jan 2017 13:02:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55916) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cS6Ba-000313-Vq for qemu-devel@nongnu.org; Fri, 13 Jan 2017 13:02:47 -0500 Date: Fri, 13 Jan 2017 16:02:43 -0200 From: Eduardo Habkost Message-ID: <20170113180243.GA3565@thinpad.lan.raisama.net> References: <20170113115651.17607-1-haozhong.zhang@intel.com> <20170113131727.GA10706@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170113131727.GA10706@stefanha-x1.localdomain> Subject: Re: [Qemu-devel] [PATCH] hw/i386: check if nvdimm is enabled before plugging List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Haozhong Zhang , qemu-devel@nongnu.org, Paolo Bonzini , Richard Henderson , "Michael S . Tsirkin" , imammedo@redhat.com, Xiao Guangrong 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 > > Signed-off-by: Haozhong Zhang > > Message-Id: 20170112110928.GF4621@stefanha-x1.localdomain > > Message-Id: 20170111093630.2088-1-stefanha@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