Re: [Qemu-devel] [PATCH v3 16/46] ivshmem: remove max_peer field

[Marc-André Lureau]

Hi

----- Original Message -----
> On 15.09.2015 18:07, address@hidden wrote:
> > From: Marc-André Lureau <address@hidden>
> > 
> > max_peer isn't really useful, it tracks the maximum received VM id, but
> > that quickly matches nb_peers, the size of the peers array. Since VM
> > come and go, there might be sparse peers so it doesn't help much in
> > general to have this value around.
> 
> Does this max_peer provide any value if VMs _don't_ come and go?
> Not that I see any.

I don't see any either.

> 
> > 
> > Signed-off-by: Marc-André Lureau <address@hidden>
> > ---
> >  hw/misc/ivshmem.c | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> > 
> > diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> > index 07f2182..cda7dce 100644
> > --- a/hw/misc/ivshmem.c
> > +++ b/hw/misc/ivshmem.c
> > @@ -90,7 +90,6 @@ typedef struct IVShmemState {
> >  
> >      Peer *peers;
> >      int nb_peers; /* how many guests we have space for */
> > -    int max_peer; /* maximum numbered peer */
> >  
> >      int vm_id;
> >      uint32_t vectors;
> > @@ -200,7 +199,7 @@ static void ivshmem_io_write(void *opaque, hwaddr addr,
> >  
> >          case DOORBELL:
> >              /* check that dest VM ID is reasonable */
> > -            if (dest > s->max_peer) {
> > +            if (dest >= s->nb_peers) {
> >                  IVSHMEM_DPRINTF("Invalid destination VM ID (%d)\n", dest);
> >                  break;
> >              }
> > @@ -574,11 +573,6 @@ static void ivshmem_read(void *opaque, const uint8_t
> > *buf, int size)
> >      /* increment count for particular guest */
> >      s->peers[incoming_posn].nb_eventfds++;
> >  
> > -    /* keep track of the maximum VM ID */
> > -    if (incoming_posn > s->max_peer) {
> > -        s->max_peer = incoming_posn;
> > -    }
> > -
> >      if (incoming_posn == s->vm_id) {
> >          s->eventfd_chr[guest_max_eventfd] = create_eventfd_chr_device(s,
> >                     &s->peers[s->vm_id].eventfds[guest_max_eventfd],
> > @@ -721,8 +715,6 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error
> > **errp)
> >          PCI_BASE_ADDRESS_MEM_PREFETCH;;
> >      Error *local_err = NULL;
> >  
> > -    s->max_peer = -1;
> > -
> >      if (s->sizearg == NULL) {
> >          s->ivshmem_size = 4 << 20; /* 4 MB default */
> >      } else {
> > 
> 
>