Re: [Qemu-devel] [PATCH] kvm/irqchip: use bitmap utility for gsi tracking

[Wei Yang <richard.weiyang@gmail.com>]

On Mon, Mar 07, 2016 at 10:47:53AM +0100, Paolo Bonzini wrote:
>On 06/03/2016 02:57, Wei Yang wrote:
>> By using utilities in bitops and bitmap, this patch tries to make it more
>> friendly to audience. No functional change.
>> 
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> ---
>>  kvm-all.c | 34 ++++++++++------------------------
>>  1 file changed, 10 insertions(+), 24 deletions(-)
>> 
>> diff --git a/kvm-all.c b/kvm-all.c
>> index bd9e764..ed3f4a2 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -90,7 +90,7 @@ struct KVMState
>>  #ifdef KVM_CAP_IRQ_ROUTING
>>      struct kvm_irq_routing *irq_routes;
>>      int nr_allocated_irq_routes;
>> -    uint32_t *used_gsi_bitmap;
>> +    unsigned long *used_gsi_bitmap;
>>      unsigned int gsi_count;
>>      QTAILQ_HEAD(msi_hashtab, KVMMSIRoute) msi_hashtab[KVM_MSI_HASHTAB_SIZE];
>>  #endif
>> @@ -951,12 +951,12 @@ typedef struct KVMMSIRoute {
>>  
>>  static void set_gsi(KVMState *s, unsigned int gsi)
>>  {
>> -    s->used_gsi_bitmap[gsi / 32] |= 1U << (gsi % 32);
>> +    set_bit(gsi, s->used_gsi_bitmap);
>>  }
>>  
>>  static void clear_gsi(KVMState *s, unsigned int gsi)
>>  {
>> -    s->used_gsi_bitmap[gsi / 32] &= ~(1U << (gsi % 32));
>> +    clear_bit(gsi, s->used_gsi_bitmap);
>>  }
>>  
>>  void kvm_init_irq_routing(KVMState *s)
>> @@ -965,17 +965,9 @@ void kvm_init_irq_routing(KVMState *s)
>>  
>>      gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1;
>>      if (gsi_count > 0) {
>> -        unsigned int gsi_bits, i;
>> -
>>          /* Round up so we can search ints using ffs */
>> -        gsi_bits = ALIGN(gsi_count, 32);
>> -        s->used_gsi_bitmap = g_malloc0(gsi_bits / 8);
>> +        s->used_gsi_bitmap = bitmap_new(gsi_count);
>>          s->gsi_count = gsi_count;
>> -
>> -        /* Mark any over-allocated bits as already in use */
>> -        for (i = gsi_count; i < gsi_bits; i++) {
>> -            set_gsi(s, i);
>> -        }
>>      }
>>  
>>      s->irq_routes = g_malloc0(sizeof(*s->irq_routes));
>> @@ -1105,9 +1097,7 @@ static void kvm_flush_dynamic_msi_routes(KVMState *s)
>>  
>>  static int kvm_irqchip_get_virq(KVMState *s)
>>  {
>> -    uint32_t *word = s->used_gsi_bitmap;
>> -    int max_words = ALIGN(s->gsi_count, 32) / 32;
>> -    int i, zeroes;
>> +    int next_virq;
>>  
>>      /*
>>       * PIC and IOAPIC share the first 16 GSI numbers, thus the available
>> @@ -1120,16 +1110,12 @@ static int kvm_irqchip_get_virq(KVMState *s)
>>      }
>>  
>>      /* Return the lowest unused GSI in the bitmap */
>> -    for (i = 0; i < max_words; i++) {
>> -        zeroes = ctz32(~word[i]);
>> -        if (zeroes == 32) {
>> -            continue;
>> -        }
>> -
>> -        return zeroes + i * 32;
>> +    next_virq = find_first_zero_bit(s->used_gsi_bitmap, s->gsi_count);
>> +    if (next_virq >= s->gsi_count) {
>> +            return -ENOSPC;
>> +    } else {
>> +            return next_virq;
>>      }
>> -    return -ENOSPC;
>> -
>>  }
>>  
>>  static KVMMSIRoute *kvm_lookup_msi_route(KVMState *s, MSIMessage msg)
>> 
>
>Queued, thanks.  I will send a pull request today.
>

Thanks, glad to contribute :-)

>Paolo

-- 
Wei Yang
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