Re: [PATCH] x86/hyperv: stash and use the configured max VP index

["Roger Pau Monné" <roger.pau@citrix.com>]

On Wed, Apr 29, 2020 at 11:47:18AM +0000, Wei Liu wrote:
> On Wed, Apr 29, 2020 at 11:41:44AM +0100, Wei Liu wrote:
> > The value returned from CPUID is the maximum number for virtual
> > processors supported by Hyper-V. It could be larger than the maximum
> > number of virtual processors configured.
> > 
> > Stash the configured number into a variable and use it in calculations.
> > 
> > Signed-off-by: Wei Liu <liuwe@microsoft.com>
> > ---
> >  xen/arch/x86/guest/hyperv/hyperv.c  | 4 ++++
> >  xen/arch/x86/guest/hyperv/private.h | 1 +
> >  xen/arch/x86/guest/hyperv/tlb.c     | 2 +-
> >  xen/arch/x86/guest/hyperv/util.c    | 2 +-
> >  4 files changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/xen/arch/x86/guest/hyperv/hyperv.c b/xen/arch/x86/guest/hyperv/hyperv.c
> > index 91a6782cd986..84221b751453 100644
> > --- a/xen/arch/x86/guest/hyperv/hyperv.c
> > +++ b/xen/arch/x86/guest/hyperv/hyperv.c
> > @@ -33,6 +33,7 @@ DEFINE_PER_CPU_READ_MOSTLY(void *, hv_input_page);
> >  DEFINE_PER_CPU_READ_MOSTLY(void *, hv_vp_assist);
> >  DEFINE_PER_CPU_READ_MOSTLY(unsigned int, hv_vp_index);
> >  
> > +unsigned int __read_mostly hv_max_vp_index;
> >  static bool __read_mostly hcall_page_ready;
> >  
> >  static uint64_t generate_guest_id(void)
> > @@ -143,6 +144,9 @@ static int setup_hypercall_pcpu_arg(void)
> >      rdmsrl(HV_X64_MSR_VP_INDEX, vp_index_msr);
> >      this_cpu(hv_vp_index) = vp_index_msr;
> >  
> > +    if ( vp_index_msr > hv_max_vp_index )
> > +        hv_max_vp_index = vp_index_msr;
> > +
> >      return 0;
> >  }
> >  
> > diff --git a/xen/arch/x86/guest/hyperv/private.h b/xen/arch/x86/guest/hyperv/private.h
> > index 354fc7f685a7..fea3e291e944 100644
> > --- a/xen/arch/x86/guest/hyperv/private.h
> > +++ b/xen/arch/x86/guest/hyperv/private.h
> > @@ -28,6 +28,7 @@
> >  DECLARE_PER_CPU(void *, hv_input_page);
> >  DECLARE_PER_CPU(void *, hv_vp_assist);
> >  DECLARE_PER_CPU(unsigned int, hv_vp_index);
> > +extern unsigned int hv_max_vp_index;
> >  
> >  static inline unsigned int hv_vp_index(unsigned int cpu)
> >  {
> > diff --git a/xen/arch/x86/guest/hyperv/tlb.c b/xen/arch/x86/guest/hyperv/tlb.c
> > index 1d723d6ee679..0a44071481bd 100644
> > --- a/xen/arch/x86/guest/hyperv/tlb.c
> > +++ b/xen/arch/x86/guest/hyperv/tlb.c
> > @@ -166,7 +166,7 @@ int hyperv_flush_tlb(const cpumask_t *mask, const void *va,
> >          {
> >              unsigned int vpid = hv_vp_index(cpu);
> >  
> > -            if ( vpid >= ms_hyperv.max_vp_index )
> > +            if ( vpid >= hv_max_vp_index )
> 
> I think the >= should be changed to > here.

I agree. With this fixed:

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks!