On Wed, Apr 08, 2020 at 05:54:35PM +0200, Vitaly Kuznetsov wrote:
> Olaf Hering <olaf@xxxxxxxxx> writes:
>
> > A few kernel features depend on ms_hyperv.misc_features, but unlike its
> > siblings ->features and ->hints, the value was never reported during boot.
> >
> > Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> > ---
> > arch/x86/kernel/cpu/mshyperv.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index caa032ce3fe3..53706fb56433 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -227,8 +227,8 @@ static void __init ms_hyperv_init_platform(void)
> > ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
> > ms_hyperv.hints = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
> >
> > - pr_info("Hyper-V: features 0x%x, hints 0x%x\n",
> > - ms_hyperv.features, ms_hyperv.hints);
> > + pr_info("Hyper-V: features 0x%x, hints 0x%x, misc 0x%x\n",
> > + ms_hyperv.features, ms_hyperv.hints, ms_hyperv.misc_features);
>
> Several spare thoughts:
>
> I'm always struggling to remember what is what here as these names don't
> correspond to TLFS, could we maybe come up with better naming, e.g.
>
> "Features.EAX", "Features.EDX", "Recommendations.EAX",...
>
> On the other hand, there is more, e.g. nested virtualization
> features. How is it useful for all users to see this in dmesg every
> time? If we need it for development purposes, we can always run 'cpuid'
> so maybe let's drop this altogether or print only with pr_debug?
>
> (Honestly: no strong opinion here, deferring to Microsoft folks).
I think making them closer to TLFS is a good idea.
Leaving them always printed is not a big concern to me. Sometimes you
don't get to run `cpuid` if the kernel crashes early.
Olaf's patch is fine as-is. I'm happy to take this patch (if not already
taken by x86 maintainers) given it makes at least one developer's life
easier.
Wei.
>
> >
> > ms_hyperv.max_vp_index = cpuid_eax(HYPERV_CPUID_IMPLEMENT_LIMITS);
> > ms_hyperv.max_lp_index = cpuid_ebx(HYPERV_CPUID_IMPLEMENT_LIMITS);
> >
>
> --
> Vitaly
>
