Re: [Qemu-devel] [PATCH V4 18/19] pci: remove hard-coded bar size in msix_init_exclusive_bar()

[Jason Wang <jasowang@redhat.com>]

On Thu, Mar 19, 2015 at 6:09 PM, Michael S. Tsirkin <mst@redhat.com> 
wrote:
> On Thu, Mar 19, 2015 at 01:19:23PM +0800, Jason Wang wrote:
>>  
>>  
>>  On Wed, Mar 18, 2015 at 8:52 PM, Michael S. Tsirkin 
>> <mst@redhat.com> wrote:
>>  >On Wed, Mar 18, 2015 at 05:35:08PM +0800, Jason Wang wrote:
>>  >> This patch let msix_init_exclusive_bar() can accept bar_size 
>> parameter
>>  >> other than a hard-coded limit 4096. Then caller can specify a 
>> bar_size
>>  >> depends on msix entries and can use up to 2048 msix entries as 
>> PCI
>>  >> spec allows. To keep migration compatibility, 4096 is used for 
>> all
>>  >> callers and pba were start from half of bar size.
>>  >> Cc: Keith Busch <keith.busch@intel.com>
>>  >> Cc: Kevin Wolf <kwolf@redhat.com>
>>  >> Cc: Stefan Hajnoczi <stefanha@redhat.com>
>>  >> Cc: Michael S. Tsirkin <mst@redhat.com>
>>  >> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>  >
>>  >Hmm this API looks strange. Caller will then have to have
>>  >msi specific knowledge.
>>  >Can't we keep the size iternal to msix.c?
>>  
>>  Looks like we can, but still need an extra parameter e.g a boolean
>>  compat_size to let msix_init_exclusive_bar() to use 4096 as bar 
>> size.
> 
> Why not just figure the size out from # of vectors?

Yes, for 2.4 we can figure the size out from the number of vectors.