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Date: Tue, 5 Jun 2018 10:42:05 -0600
From: Ross Zwisler <ross.zwisler@linux.intel.com>
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Subject: Re: [Qemu-devel] [qemu PATCH v4 3/4] nvdimm,
 acpi: support NFIT platform capabilities
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>, Igor Mammedov <imammedo@redhat.com>, qemu-devel@nongnu.org, Haozhong Zhang <haozhong.zhang@intel.com>, Stefan Hajnoczi <stefanha@redhat.com>, Eduardo Habkost <ehabkost@redhat.com>, linux-nvdimm <linux-nvdimm@lists.01.org>, "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>

On Tue, Jun 05, 2018 at 06:25:27PM +0300, Michael S. Tsirkin wrote:
> On Mon, May 21, 2018 at 10:32:02AM -0600, Ross Zwisler wrote:
> > Add a machine command line option to allow the user to control the Platform
> > Capabilities Structure in the virtualized NFIT.  This Platform Capabilities
> > Structure was added in ACPI 6.2 Errata A.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> 
> I tried playing with it and encoding the capabilities is
> quite awkward.
> 
> Can we add bits for specific capabilities instead of nvdimm-cap?
> 
> How about:
> 
> "cpu-flush-on-power-loss-cap"
> "memory-flush-on-power-loss-cap"
> "byte-addressable-mirroring-cap"

Hmmm...I don't like that as much because:

a) It's very verbose.  Looking at my current qemu command line few other
   options require that many characters, and you'd commonly be defining more
   than one of these for a given VM.

b) It means that the QEMU will need to be updated if/when new flags are added,
   because we'll have to have new options for each flag.  The current
   implementation is more future-proof because you can specify any flags
   value you want.

However, if you feel strongly about this, I'll make the change.