On Thu, Nov 12, 2020 at 04:16:30PM +0100, Vitaly Kuznetsov wrote:
[...]
> > /*
> > * Virtual processor will never share a physical core with another virtual
> > * processor, except for virtual processors that are reported as sibling
> > SMT
> > diff --git a/arch/x86/include/asm/mshyperv.h
> > b/arch/x86/include/asm/mshyperv.h
> > index ffc289992d1b..ac2b0d110f03 100644
> > --- a/arch/x86/include/asm/mshyperv.h
> > +++ b/arch/x86/include/asm/mshyperv.h
> > @@ -237,6 +237,8 @@ int hyperv_fill_flush_guest_mapping_list(
> > struct hv_guest_mapping_flush_list *flush,
> > u64 start_gfn, u64 end_gfn);
> >
> > +extern bool hv_root_partition;
>
> Eventually this is not going to be an x86 only thing I believe?
I hope so. :-)
>
> > +
> > #ifdef CONFIG_X86_64
> > void hv_apic_init(void);
> > void __init hv_init_spinlocks(void);
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index 05ef1f4550cb..f7633e1e4c82 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -237,6 +237,22 @@ static void __init ms_hyperv_init_platform(void)
> > pr_debug("Hyper-V: max %u virtual processors, %u logical processors\n",
> > ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
> >
> > + /*
> > + * Check CPU management privilege.
> > + *
> > + * To mirror what Windows does we should extract CPU management
> > + * features and use the ReservedIdentityBit to detect if Linux is the
> > + * root partition. But that requires negotiating CPU management
> > + * interface (a process to be finalized).
> > + *
> > + * For now, use the privilege flag as the indicator for running as
> > + * root.
> > + */
> > + if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_CPU_MANAGEMENT) {
>
> We may want to cache cpuid_ebx(HYPERV_CPUID_FEATURES) somewhere but we
> already had a discussion regading naming for these caches and decided to
> wait until TLFS for ARM is out so we don't need to rename again.
Exactly.
Wei.
