Re: [Xen-devel] [RFC v1 11/15] vmx: Add a global wake-up vector for VT-d Posted-Interrupts

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Wu, Feng
> Sent: Wednesday, March 25, 2015 8:32 PM
> 
> This patch adds a global vector which is used to wake up
> the blocked vCPU when an interrupt is being posted to it.
> 
> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> Suggested-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
> ---
>  xen/arch/x86/hvm/vmx/vmx.c        | 33
> +++++++++++++++++++++++++++++++++
>  xen/include/asm-x86/hvm/hvm.h     |  1 +
>  xen/include/asm-x86/hvm/vmx/vmx.h |  3 +++
>  xen/include/xen/sched.h           |  2 ++
>  4 files changed, 39 insertions(+)
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index ff5544d..b2b4c26 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -89,6 +89,7 @@ DEFINE_PER_CPU(struct list_head,
> blocked_vcpu_on_cpu);
>  DEFINE_PER_CPU(spinlock_t, blocked_vcpu_on_cpu_lock);
> 
>  uint8_t __read_mostly posted_intr_vector;
> +uint8_t __read_mostly pi_wakeup_vector;
> 
>  static int vmx_domain_initialise(struct domain *d)
>  {
> @@ -131,6 +132,8 @@ static int vmx_vcpu_initialise(struct vcpu *v)
>      if ( v->vcpu_id == 0 )
>          v->arch.user_regs.eax = 1;
> 
> +    INIT_LIST_HEAD(&v->blocked_vcpu_list);
> +
>      return 0;
>  }
> 
> @@ -1834,11 +1837,19 @@ const struct hvm_function_table * __init
> start_vmx(void)
>      }
> 
>      if ( cpu_has_vmx_posted_intr_processing )
> +    {
>          alloc_direct_apic_vector(&posted_intr_vector,
> event_check_interrupt);
> +
> +        if ( iommu_intpost )
> +            alloc_direct_apic_vector(&pi_wakeup_vector,
> pi_wakeup_interrupt);
> +        else
> +            vmx_function_table.pi_desc_update = NULL;
> +    }

just style issue. Above conditional logic looks not intuitive to me.
usually we have:
        if ( iommu_intpost )
                vmx_function_table.pi_desc_update = func;
        else
                vmx_function_table.pi_desc_update = NULL;

suppose you will register callback in later patch. then better to
move the NULL one there too. Putting it here doesn't meet the
normal if...else implications. :-)

>      else
>      {
>          vmx_function_table.deliver_posted_intr = NULL;
>          vmx_function_table.sync_pir_to_irr = NULL;
> +        vmx_function_table.pi_desc_update = NULL;
>      }
> 
>      if ( cpu_has_vmx_ept
> @@ -3255,6 +3266,28 @@ void vmx_vmenter_helper(const struct
> cpu_user_regs *regs)
>  }
> 
>  /*
> + * Handle VT-d posted-interrupt when VCPU is blocked.
> + */
> +void pi_wakeup_interrupt(struct cpu_user_regs *regs)
> +{
> +    struct vcpu *v;
> +    int cpu = smp_processor_id();
> +
> +    spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, cpu));
> +    list_for_each_entry(v, &per_cpu(blocked_vcpu_on_cpu, cpu),
> +                    blocked_vcpu_list) {
> +        struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
> +
> +        if ( pi_test_on(pi_desc) == 1 )
> +            tasklet_schedule(&v->vcpu_wakeup_tasklet);

why can't we directly call vcpu_unblock here?

> +    }
> +    spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, cpu));
> +
> +    ack_APIC_irq();
> +    this_cpu(irq_count)++;
> +}
> +
> +/*
>   * Local variables:
>   * mode: C
>   * c-file-style: "BSD"
> diff --git a/xen/include/asm-x86/hvm/hvm.h
> b/xen/include/asm-x86/hvm/hvm.h
> index 0dc909b..a11a256 100644
> --- a/xen/include/asm-x86/hvm/hvm.h
> +++ b/xen/include/asm-x86/hvm/hvm.h
> @@ -195,6 +195,7 @@ struct hvm_function_table {
>      void (*deliver_posted_intr)(struct vcpu *v, u8 vector);
>      void (*sync_pir_to_irr)(struct vcpu *v);
>      void (*handle_eoi)(u8 vector);
> +    void (*pi_desc_update)(struct vcpu *v, int new_state);
> 
>      /*Walk nested p2m  */
>      int (*nhvm_hap_walk_L1_p2m)(struct vcpu *v, paddr_t L2_gpa,
> diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h
> b/xen/include/asm-x86/hvm/vmx/vmx.h
> index e643c3c..f4296ab 100644
> --- a/xen/include/asm-x86/hvm/vmx/vmx.h
> +++ b/xen/include/asm-x86/hvm/vmx/vmx.h
> @@ -34,6 +34,7 @@ DECLARE_PER_CPU(struct list_head,
> blocked_vcpu_on_cpu);
>  DECLARE_PER_CPU(spinlock_t, blocked_vcpu_on_cpu_lock);
> 
>  extern uint8_t posted_intr_vector;
> +extern uint8_t pi_wakeup_vector;
> 
>  typedef union {
>      struct {
> @@ -574,6 +575,8 @@ int alloc_p2m_hap_data(struct p2m_domain *p2m);
>  void free_p2m_hap_data(struct p2m_domain *p2m);
>  void p2m_init_hap_data(struct p2m_domain *p2m);
> 
> +void pi_wakeup_interrupt(struct cpu_user_regs *regs);
> +
>  /* EPT violation qualifications definitions */
>  #define _EPT_READ_VIOLATION         0
>  #define EPT_READ_VIOLATION          (1UL<<_EPT_READ_VIOLATION)
> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
> index c874dd4..91f0912 100644
> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -148,6 +148,8 @@ struct vcpu
> 
>      struct vcpu     *next_in_list;
> 
> +    struct list_head blocked_vcpu_list;
> +
>      s_time_t         periodic_period;
>      s_time_t         periodic_last_event;
>      struct timer     periodic_timer;
> --
> 2.1.0


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