From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>
> Wei Liu <wei.liu@xxxxxxxxxx> writes:
>
> > Hi all
> >
> > During my work to make Linux boot as root partition on MSHV, I found out
> > that a privilege mask was not collected in ms_hyperv_info.
> >
> > Looking at the code, the field names of ms_hyperv_info are not
> > consistent with the names defined in TLFS. That makes it difficult to
> > choose a name for the field that stores the privilege mask.
> >
> > I've got a local patch to make the existing fields closer to TLFS. The
> > suffix "_a" means the value comes from EAX.
> >
> > Given that this structure is also used on ARM, so having x86 suffix is
> > probably not the best idea. Do people care?
> >
> > diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> > index c57799684170..913af5e93cce 100644
> > --- a/include/asm-generic/mshyperv.h
> > +++ b/include/asm-generic/mshyperv.h
> > @@ -26,9 +26,9 @@
> > #include <asm/hyperv-tlfs.h>
> >
> > struct ms_hyperv_info {
> > - u32 features;
> > - u32 misc_features;
> > - u32 hints;
> > + u32 features_a;
> > + u32 features_d;
> > + u32 recommendations;
> > u32 nested_features;
> > u32 max_vp_index;
> > u32 max_lp_index;
> >
> > Any comment on this? I'm normally bad at naming things so any suggestion
> > is welcomed.
>
> My take: let's avoid ambiguous '_a', '_d' and use full register names,
> it's only three letters after all. Let's also avoid suffix-less names as
> eventually we'll need to add non-eax parts. That is:
>
> u32 features_eax;
> u32 features_edx;
> u32 recommendations_eax;
> u32 nested_features_eax;
> ...
>
> I would also feel comfortable with these names sortened,
>
> u32 feat_eax;
> u32 feat_edx;
> u32 recomm_eax;
> u32 nested_feat_eax;
> ...
>
This is in the asm-generic portion of mshyperv.h, so it is shared
across the x86 and ARM64 architectures. So I don't think we
want x86 register names. On ARM64, the eax/ebx/ecx/edx
portions are retrieved all together in a single 128-bit register
read. I abstracted this into four 32-bit parts labeled
"a", "b", "c", and "d" with the obvious mapping to
eax/ebx/ecx/edx on the x86 side, but without using those names.
We don't have a TLFS for ARM64 (should be coming soon). Might
be worth seeing what naming, if any, will be used there.
Michael
