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

[Wei Liu <wl@xxxxxxx>]

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@xxxxxxxxxxxxx>
> ---
>  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.

Wei.

>              {
>                  local_irq_restore(irq_flags);
>                  return -ENXIO;
> diff --git a/xen/arch/x86/guest/hyperv/util.c 
> b/xen/arch/x86/guest/hyperv/util.c
> index bec61c2afd87..2c5f421b7bd9 100644
> --- a/xen/arch/x86/guest/hyperv/util.c
> +++ b/xen/arch/x86/guest/hyperv/util.c
> @@ -33,7 +33,7 @@ int cpumask_to_vpset(struct hv_vpset *vpset,
>  {
>      int nr = 1;
>      unsigned int cpu, vcpu_bank, vcpu_offset;
> -    unsigned int max_banks = ms_hyperv.max_vp_index / 64;
> +    unsigned int max_banks = hv_max_vp_index / 64;
>  
>      /* Up to 64 banks can be represented by valid_bank_mask */
>      if ( max_banks > 64 )
> -- 
> 2.20.1
>