On Sat, Oct 12, 2019 at 09:31:25AM +0800, Xiaoyao Li wrote:
> On 10/12/2019 9:21 AM, Eduardo Habkost wrote:
> > On Sat, Oct 12, 2019 at 09:15:56AM +0800, Xiaoyao Li wrote:
> > > On 10/12/2019 2:21 AM, Eduardo Habkost wrote:
> > > > On Fri, Oct 11, 2019 at 10:53:49PM +0800, Xiaoyao Li wrote:
> > > > > Add new version of Snowridge CPU model that removes MPX feature.
> > > > >
> > > > > MPX support is being phased out by Intel. GCC has dropped it, Linux
> > > > > kernel
> > > > > and kvm are also going to do that in the future.
> > > > >
> > > > > Signed-off-by: Xiaoyao Li <xiaoyao...@intel.com>
> > > > > ---
> > > > > Changes in v2:
> > > > > - Use CPU model versioning mechanism instead of machine-type
> > > > > compat
> > > > > ---
> > > > > target/i386/cpu.c | 13 +++++++++++++
> > > > > 1 file changed, 13 insertions(+)
> > > > >
> > > > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > > > > index 44f1bbdcac76..27b0a17b46a8 100644
> > > > > --- a/target/i386/cpu.c
> > > > > +++ b/target/i386/cpu.c
> > > > > @@ -2793,6 +2793,19 @@ static X86CPUDefinition builtin_x86_defs[] = {
> > > > > CPUID_6_EAX_ARAT,
> > > > > .xlevel = 0x80000008,
> > > > > .model_id = "Intel Atom Processor (SnowRidge)",
> > > > > + .versions = (X86CPUVersionDefinition[]) {
> > > > > + { .version = 1 },
> > > > > + {
> > > > > + .version = 2,
> > > > > + .alias = "Snowridge-noMPX",
> > > >
> > > > The intention is to stop creating new funny names for CPU model
> > > > variations, now, and stick to -v1, -v2, -v3, etc.
> > > >
> > > > The .alias field is optional, and was added only for
> > > > compatibility with the existing -noTSX and -IBRS CPU models.
> > >
> > > Got it.
> > >
> > > > > + .props = (PropValue[]) {
> > > > > + { "mpx", "off" },
> > > > > + { "model-id", "Intel Atom Processor (Snowridge,
> > > > > no MPX)" },
> > > >
> > > > Do you think it's important to report a different model-id?
> > > > I would keep it the same and only add mpx=off.
> > >
> > > I just want to let user know easily the differences between Snowridge-v1
> > > and
> > > Snowridge-v2. Unfortunately, it seems ugly.
> > >
> > > When testing with Cascadelake-Server, it puzzles every time that which one
> > > should I choose between Cascadelake-Server-v1 and Cascadelake-Server-v2.
> > > From the output of "-cpu ?", I don't know the differences between them.
> > > Everytime I have to go to the source code to see the difference.
> > >
> > > Maybe there is a way to see/report the differences between different
> > > versions of the same CPU model that I just don't know?
> >
> > Good point. I forgot that model-id is also the model description
> > in "-cpu ?".
> >
> > Well, it doesn't hurt to have a different model-id in v2 that's
> > more informative. Feel free to keep the model-id line in v3.
>
> OK. I will send out the v3 patch keeping the model-id while removing the
> alias.
>
> BTW, do you have better idea to tell the differences among versions of the
> same CPU model?
We could add a new field for a human-readable description of the
CPU model version, and print that field on "-cpu help" if set.
We could also try to generate a description automatically (e.g.
automatically describe SnowRidge-v2 as "SnowRidge-v1 plus mpx"
based on .props). I'm not sure if it would be worth the effort,
though.
--
Eduardo
