On Mon, Mar 25, 2013 at 04:15:15PM +0100, Igor Mammedov wrote:
> On Mon, 25 Mar 2013 10:39:36 +0100
> Andreas Färber <afaer...@suse.de> wrote:
>
> > Am 28.02.2013 03:12, schrieb H. Peter Anvin:
> > > From: "H. Peter Anvin" <h...@zytor.com>
> > >
> > > Add models for 486SX, and pre-CPUID versions of the 486 (DX & SX).
> > > Change the model number for the standard 486DX to a model which
> > > actually had CPUID.
> > >
> > > Note: these models are fairly vestigial, for example most of the FPU
> > > operations still work; only F*ST[CS]W have been modified to appear as
> > > through there is no FPU.
> > >
> > > This also changes the classic 486 model number to 8 (DX4) which
> > > matches the feature set presented.
> > >
> > > Signed-off-by: H. Peter Anvin <h...@zytor.com>
[...]
> > > + },
> > > + {
> > > .name = "486",
> > > .level = 1,
> > > .vendor = CPUID_VENDOR_INTEL,
> > > .family = 4,
> > > - .model = 0,
> > > + .model = 8,
> >
> > Such changes have been rejected in the past (e.g., n270 Atom).
> > I personally wouldn't object to 486 changes, but I guess it should
> > rather be handled via Igor's CPU static properties that I have in my
> > review queue: The .model value would be set to 8 but the PC machine
> > would be changed alongside to set model = 0 for pc-1.4 and earlier.
> It doesn't relates to property refactoring nor to slim CPU sub-classes
> conversion either. So it could go in independently.
>
> But is this change safe from migration POV?
Migration is exactly the reason we can't include this as-is, and where
having static properties would be useful. We need to keep model=0 on the
pc-1.3 and older machine-types, and set model=8 only on pc-1.4 and
newer.
With static properties we can simply set it using the compat_props
table; without static properties, we need a compatibility function or
global variable to enable the model=0 behavior.
>
> >
> > > .stepping = 0,
> > > .features = I486_FEATURES,
> > > .xlevel = 0,
> > > },
--
Eduardo
