Re:Re: [PATCH] KVM: arm/arm64 : add lpi info in vgic-debug

[<peng.hao2@zte.com.cn>]

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>On 23/03/18 10:36, Peng Hao wrote:
>> Add lpi debug info to vgic-stat.
>> the printed info like this:
>>      SPI  287      0 000001        0        0   0 160      -1
>>      LPI 8192      2 000100        0        0   0 160      -1
>> 
>> Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
>> ---
>>  virt/kvm/arm/vgic/vgic-debug.c | 61 ++++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 56 insertions(+), 5 deletions(-)
>> 
>> diff --git a/virt/kvm/arm/vgic/vgic-debug.c b/virt/kvm/arm/vgic/vgic-debug.c
>> index 10b3817..444115e 100644
>> --- a/virt/kvm/arm/vgic/vgic-debug.c
>> +++ b/virt/kvm/arm/vgic/vgic-debug.c
>> @@ -36,9 +36,12 @@
>>  struct vgic_state_iter {
>>      int nr_cpus;
>>      int nr_spis;
>> +    int nr_lpis;
>>      int dist_id;
>>      int vcpu_id;
>>      int intid;
>> +    int lpi_print_count;
>> +    struct vgic_irq **lpi_irqs;
>>  };
>>  
>>  static void iter_next(struct vgic_state_iter *iter)
>> @@ -52,6 +55,40 @@ static void iter_next(struct vgic_state_iter *iter)
>>      if (iter->intid == VGIC_NR_PRIVATE_IRQS &&
>>          ++iter->vcpu_id < iter->nr_cpus)
>>          iter->intid = 0;
>> +
>> +    if (iter->intid >= VGIC_NR_PRIVATE_IRQS + iter->nr_spis) {
>> +        if (iter->lpi_print_count < iter->nr_lpis)
>> +            iter->intid = iter->lpi_irqs[iter->lpi_print_count]->intid;
>> +        iter->lpi_print_count++;
>> +    }
>> +}
>> +
>> +static void vgic_debug_get_lpis(struct kvm *kvm, struct vgic_state_iter *iter)
>> +{
>> +    struct vgic_dist *dist = &kvm->arch.vgic;
>> +    int i = 0;
>> +    struct vgic_irq *irq = NULL, **lpi_irqs;
>> +
>> +again:
>> +    iter->nr_lpis = dist->lpi_list_count;
>> +    lpi_irqs = kmalloc_array(iter->nr_lpis, sizeof(irq), GFP_KERNEL);
>> +    if (!lpi_irqs) {
>> +        iter->nr_lpis = 0;
>> +        return;
>> +    }
>> +    spin_lock(&dist->lpi_list_lock);
>> +    if (iter->nr_lpis != dist->lpi_list_count) {
>> +        kfree(lpi_irqs);
>> +        spin_unlock(&dist->lpi_list_lock);
>> +        goto again;
>> +    }

>Why do we need an exact count? It is fine to have a transient count, and
>the debug code should be able to come with that without performing this
>terrible loop.
yeah, it is enough to have a rough count for debug code .
>We also already have some code that snapshot the the LPIs (see
>vgic_copy_lpi_list), so please consider reusing that instead.
I can't reuse vgic_copy_lpi_list. It snapshots based on LPI's target vcpu. 
>> +
>> +    list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
>> +        vgic_get_irq_kref(irq);
>> +        lpi_irqs[i++] = irq;
>> +    }
>> +    spin_unlock(&dist->lpi_list_lock);
>> +    iter->lpi_irqs = lpi_irqs;

>Messing with the internals of the refcounts is really a bad idea. Please
>use vgic_get_irq() in conjunction with the above, and allow it to fail
>gracefully.
  vgic_get_irq require intid as input  and vgic_get_lpi that vgic_get_irq calling will traverse the lpi_list with holding lpi_list_lock again,
  but here I has held lpi_list_lock. So I think calling vgic_get_irq_kref is safe with holding the
 lpi_list_lock. 
> >  }
> >  
>>  static void iter_init(struct kvm *kvm, struct vgic_state_iter *iter,
>> @@ -64,6 +101,8 @@ static void iter_init(struct kvm *kvm, struct vgic_state_iter *iter,
>>      iter->nr_cpus = nr_cpus;
>>      iter->nr_spis = kvm->arch.vgic.nr_spis;
>>  
>> +    if (vgic_supports_direct_msis(kvm) && !pos)
>> +        vgic_debug_get_lpis(kvm, iter);
>>      /* Fast forward to the right position if needed */
>>      while (pos--)
>>          iter_next(iter);
>> @@ -73,7 +112,9 @@ static bool end_of_vgic(struct vgic_state_iter *iter)
>>  {
>>      return iter->dist_id > 0 &&
>>          iter->vcpu_id == iter->nr_cpus &&
>> -        (iter->intid - VGIC_NR_PRIVATE_IRQS) == iter->nr_spis;
>> +        (iter->intid - VGIC_NR_PRIVATE_IRQS) >= iter->nr_spis &&
>> +        ((iter->nr_lpis == 0) ||
>> +        (iter->lpi_print_count == iter->nr_lpis + 1));
>>  }
>>  
>>  static void *vgic_debug_start(struct seq_file *s, loff_t *pos)
>> @@ -130,6 +171,7 @@ static void vgic_debug_stop(struct seq_file *s, void *v)
>>  
>>      mutex_lock(&kvm->lock);
>>      iter = kvm->arch.vgic.iter;
>> +    kfree(iter->lpi_irqs);
>>      kfree(iter);
>>      kvm->arch.vgic.iter = NULL;
>>      mutex_unlock(&kvm->lock);
>> @@ -154,7 +196,7 @@ static void print_header(struct seq_file *s, struct vgic_irq *irq,
>>               struct kvm_vcpu *vcpu)
>>  {
>>      int id = 0;
>> -    char *hdr = "SPI ";
>> +    char *hdr = "S/LPI ";
>>  
>>      if (vcpu) {
>>          hdr = "VCPU";
>> @@ -162,7 +204,10 @@ static void print_header(struct seq_file *s, struct vgic_irq *irq,
>>      }
>>  
>>      seq_printf(s, "\n");
>> -    seq_printf(s, "%s%2d TYP   ID TGT_ID PLAEHC     HWID   TARGET SRC PRI VCPU_ID\n", hdr, id);
>> +    if (vcpu)
>> +        seq_printf(s, "%s%2d TYP   ID TGT_ID PLAEHC     HWID   TARGET SRC PRI VCPU_ID\n", hdr, id);
>> +    else
>> +        seq_printf(s, "%s TYP   ID TGT_ID PLAEHC     HWID   TARGET SRC PRI VCPU_ID\n", hdr);

>This feels like an unnecessary change. But if you really want that kind
>of detail, change your "S/LPI" to say something more generic, such as
>"Global".
  I modify this just for aligned print output. "Global" is great.
>> seq_printf(s, "---------------------------------------------------------------\n");>  }
>>  
>> @@ -174,8 +219,10 @@ static void print_irq_state(struct seq_file *s, struct vgic_irq *irq,
>>          type = "SGI";
>>      else if (irq->intid < VGIC_NR_PRIVATE_IRQS)
>>          type = "PPI";
>> -    else
>> +    else if (irq->intid < VGIC_MAX_SPI)
>>          type = "SPI";
>> +    else if (irq->intid >= VGIC_MIN_LPI)
>> +        type = "LPI";
>>  
>>      if (irq->intid ==0 || irq->intid == VGIC_NR_PRIVATE_IRQS)
>>          print_header(s, irq, vcpu);
>> @@ -220,7 +267,9 @@ static int vgic_debug_show(struct seq_file *s, void *v)
>>      if (!kvm->arch.vgic.initialized)
>>          return 0;
>>  
>> -    if (iter->vcpu_id < iter->nr_cpus) {
>> +    if (iter->intid >= VGIC_MIN_LPI)
>> +        irq = iter->lpi_irqs[iter->lpi_print_count - 1];
>> +    else if (iter->vcpu_id < iter->nr_cpus) {
>>          vcpu = kvm_get_vcpu(kvm, iter->vcpu_id);
>>          irq = &vcpu->arch.vgic_cpu.private_irqs[iter->intid];
>>      } else {
>> @@ -230,6 +279,8 @@ static int vgic_debug_show(struct seq_file *s, void *v)
>>      spin_lock(&irq->irq_lock);
>>      print_irq_state(s, irq, vcpu);
>>      spin_unlock(&irq->irq_lock);
>> +    if (iter->intid >= VGIC_MIN_LPI)
>> +        vgic_put_irq(kvm, irq);

>If you adopt the scheme I outlined above, you can have a balanced
>get/put behaviour, irrespective of the interrupt type, and a much nicer
>result.
yeah, "if (iter->intid >= VGIC_MIN_LPI)" is unnecessary.  
>>      return 0;
>>  }
>> 

>Thanks,

>    M.

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