On Tue, Jun 5, 2018 at 3:07 PM, Ross Zwisler
<ross.zwis...@linux.intel.com> wrote:
> On Tue, Jun 05, 2018 at 09:37:25PM +0300, Michael S. Tsirkin wrote:
>> On Tue, Jun 05, 2018 at 11:15:00AM -0700, Dan Williams wrote:
>> > On Tue, Jun 5, 2018 at 9:42 AM, Ross Zwisler
>> > <ross.zwis...@linux.intel.com> wrote:
>> > > 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.zwis...@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.
>> >
>> > Straw-man: Could we do something similar with what we are doing in ndctl?
>> >
>> > enum ndctl_persistence_domain {
>> > PERSISTENCE_NONE = 0,
>> > PERSISTENCE_MEM_CTRL = 10,
>> > PERSISTENCE_CPU_CACHE = 20,
>> > PERSISTENCE_UNKNOWN = INT_MAX,
>> > };
>> >
>> > ...and have the command line take a number where "10" and "20" are
>> > supported today, but allows us to adapt to new persistence domains in
>> > the future.
>>
>> I'm fine with that except can we have symbolic names instead of numbers
>> on command line?
>>
>> --
>> MST
>
> Okay, we can move to the symbolic names. Do you want them to be that long, or
> would:
>
> nvdimm-cap-cpu
> nvdimm-cap-mem-ctrl
> nvdimm-cap-mirroring
Wait, why is mirroring part of this?
I was thinking this option would be:
--persistence-domain={cpu,mem-ctrl}
...and try not to let ACPI specifics leak into the qemu command line
interface. For example PowerPC qemu could have a persistence domain
communicated via Open Firmware or some other mechanism.
>
> or something be better?
