Re: [Qemu-devel] [PATCH v3 41/46] ivshmem: do not keep shm_fd open

[Claudio Fontana <claudio.fontana@huawei.com>]

On 22.09.2015 16:59, Marc-André Lureau wrote:
> Hi
> 
> ----- Original Message -----
>> On 15.09.2015 18:07, marcandre.lureau@redhat.com wrote:
>>> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>>>
>>> Remove shm_fd from device state, closing it as early as possible to avoid
>>> leaks.
>>>
>>> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>>> ---
>>>  hw/misc/ivshmem.c | 14 +++++---------
>>>  1 file changed, 5 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
>>> index 4adcac5..f9ac955 100644
>>> --- a/hw/misc/ivshmem.c
>>> +++ b/hw/misc/ivshmem.c
>>> @@ -88,7 +88,6 @@ typedef struct IVShmemState {
>>>      MemoryRegion ivshmem;
>>>      uint64_t ivshmem_size; /* size of shared memory region */
>>>      uint32_t ivshmem_64bit;
>>> -    int shm_fd; /* shared memory file descriptor */
>>
>> is it in no way useful during debugging to have access to this field?
>> Or is it easily available elsewhere?
> 
> How would it be useful during debugging? Once the memory is mapped there isn't much you can do with it, it's just keeping a fd open, isn't it?

all right.

> 
>>
>> Ciao C.
>>
>>>  
>>>      Peer *peers;
>>>      int nb_peers; /* how many peers we have space for */
>>> @@ -235,7 +234,7 @@ static uint64_t ivshmem_io_read(void *opaque, hwaddr
>>> addr,
>>>  
>>>          case IVPOSITION:
>>>              /* return my VM ID if the memory is mapped */
>>> -            if (s->shm_fd >= 0) {
>>> +            if (memory_region_is_mapped(&s->ivshmem)) {
>>>                  ret = s->vm_id;
>>>              } else {
>>>                  ret = -1;
>>> @@ -356,8 +355,6 @@ static int create_shared_memory_BAR(IVShmemState *s,
>>> int fd, uint8_t attr,
>>>          return -1;
>>>      }
>>>  
>>> -    s->shm_fd = fd;
>>> -
>>>      memory_region_init_ram_ptr(&s->ivshmem, OBJECT(s), "ivshmem.bar2",
>>>                                 s->ivshmem_size, ptr);
>>>      vmstate_register_ram(&s->ivshmem, DEVICE(s));
>>> @@ -535,7 +532,7 @@ static void ivshmem_read(void *opaque, const uint8_t
>>> *buf, int size)
>>>      if (incoming_posn == -1) {
>>>          void * map_ptr;
>>>  
>>> -        if (s->shm_fd >= 0) {
>>> +        if (memory_region_is_mapped(&s->ivshmem)) {
>>>              error_report("shm already initialized");
>>>              close(incoming_fd);
>>>              return;
>>> @@ -564,9 +561,7 @@ static void ivshmem_read(void *opaque, const uint8_t
>>> *buf, int size)
>>>  
>>>          memory_region_add_subregion(&s->bar, 0, &s->ivshmem);
>>>  
>>> -        /* only store the fd if it is successfully mapped */
>>> -        s->shm_fd = incoming_fd;
>>> -
>>> +        close(incoming_fd);
>>>          return;
>>>      }
>>>  
>>> @@ -827,6 +822,7 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error
>>> **errp)
>>>          }
>>>  
>>>          create_shared_memory_BAR(s, fd, attr, errp);
>>> +        close(fd);
>>>      }
>>>  }
>>>  
>>> @@ -842,7 +838,7 @@ static void pci_ivshmem_exit(PCIDevice *dev)
>>>          error_free(s->migration_blocker);
>>>      }
>>>  
>>> -    if (s->shm_fd >= 0) {
>>> +    if (memory_region_is_mapped(&s->ivshmem)) {
>>>          void *addr = memory_region_get_ram_ptr(&s->ivshmem);
>>>  
>>>          vmstate_unregister_ram(&s->ivshmem, DEVICE(dev));
>>>