On Tue, Sep 15, 2020 at 01:14:16PM +0200, Vitaly Kuznetsov wrote:
> Wei Liu <wei.liu@xxxxxxxxxx> writes:
>
> > Microsoft Hypervisor requires the root partition to make a few
> > hypercalls to setup application processors before they can be used.
> >
> > Signed-off-by: Lillian Grassin-Drake <ligrassi@xxxxxxxxxxxxx>
> > Signed-off-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx>
> > Co-Developed-by: Lillian Grassin-Drake <ligrassi@xxxxxxxxxxxxx>
> > Co-Developed-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx>
> > Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
> > ---
> > CPU hotplug and unplug is not yet supported in this setup, so those
> > paths remain untouched.
> > ---
> > arch/x86/kernel/cpu/mshyperv.c | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index 1bf57d310f78..7522cae02759 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -203,6 +203,31 @@ static void __init hv_smp_prepare_boot_cpu(void)
> > hv_init_spinlocks();
> > #endif
> > }
> > +
> > +static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
> > +{
> > +#if defined(CONFIG_X86_64)
>
> I think it makes little sense to try to make Linux work as Hyper-V root
> partition when !CONFIG_X86_64. If we still care about Hyper-V enablement
> for !CONFIG_X86_64 we can probably introduce something like
> CONFIG_HYPERV_ROOT and enable it automatically, e.g.
>
> config HYPERV_ROOT
> def_bool HYPERV && X86_64
>
> and use it instead.
>
We have a patch for such a config option in the /dev/mshv patch set. But
that's not yet included here so I will keep this as-is.
> > + int i;
> > + int vp_index = 1;
> > + int ret;
> > +
> > + native_smp_prepare_cpus(max_cpus);
> > +
> > + for_each_present_cpu(i) {
> > + if (i == 0)
> > + continue;
> > + ret = hv_call_add_logical_proc(numa_cpu_node(i), i, cpu_physical_id(i));
> > + BUG_ON(ret);
> > + }
> > +
> > + for_each_present_cpu(i) {
> > + if (i == 0)
> > + continue;
> > + ret = hv_call_create_vp(numa_cpu_node(i), hv_current_partition_id, vp_index++, i);
>
> So vp_index variable is needed here to make sure there are no gaps? (or
> we could've just used 'i')?
Not sure. I didn't write the original code in this function. The last
argument (i) is the logical processor index.
I don't see a reason why vp_index and lp_index can't be the same. I will
try dropping vp_index. If that works then great; if not, I will keep the
code as-is.
Sunil, if you have more insight, please chime in.
Wei.
>
> > + BUG_ON(ret);
> > + }
> > +#endif
> > +}
> > #endif
> >
> > static void __init ms_hyperv_init_platform(void)
> > @@ -359,6 +384,8 @@ static void __init ms_hyperv_init_platform(void)
> >
> > # ifdef CONFIG_SMP
> > smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
> > + if (hv_root_partition)
> > + smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
> > # endif
> >
> > /*
>
> --
> Vitaly
>
