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

["Michael S. Tsirkin" <mst@redhat.com>]

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?

> >
> >
> >> ---
> >>  hw/block/nvme.c        |  2 +-
> >>  hw/misc/ivshmem.c      |  2 +-
> >>  hw/pci/msix.c          | 18 +++++++-----------
> >>  hw/virtio/virtio-pci.c |  2 +-
> >>  include/hw/pci/msix.h  |  2 +-
> >>  5 files changed, 11 insertions(+), 15 deletions(-)
> >> diff --git a/hw/block/nvme.c b/hw/block/nvme.c
> >> index 0f3dfb9..09d7884 100644
> >> --- a/hw/block/nvme.c
> >> +++ b/hw/block/nvme.c
> >> @@ -787,7 +787,7 @@ static int nvme_init(PCIDevice *pci_dev)
> >>      pci_register_bar(&n->parent_obj, 0,
> >>          PCI_BASE_ADDRESS_SPACE_MEMORY | PCI_BASE_ADDRESS_MEM_TYPE_64,
> >>          &n->iomem);
> >> -    msix_init_exclusive_bar(&n->parent_obj, n->num_queues, 4);
> >> +    msix_init_exclusive_bar(&n->parent_obj, n->num_queues, 4, 4096);
> >>      id->vid = cpu_to_le16(pci_get_word(pci_conf + PCI_VENDOR_ID));
> >>      id->ssvid = cpu_to_le16(pci_get_word(pci_conf +
> >>PCI_SUBSYSTEM_VENDOR_ID));
> >> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> >> index 5d272c8..3e2a2d4 100644
> >> --- a/hw/misc/ivshmem.c
> >> +++ b/hw/misc/ivshmem.c
> >> @@ -631,7 +631,7 @@ static uint64_t ivshmem_get_size(IVShmemState * s)
> >>{
> >>  static void ivshmem_setup_msi(IVShmemState * s)
> >>  {
> >> -    if (msix_init_exclusive_bar(PCI_DEVICE(s), s->vectors, 1)) {
> >> +    if (msix_init_exclusive_bar(PCI_DEVICE(s), s->vectors, 1, 4096)) {
> >>          IVSHMEM_DPRINTF("msix initialization failed\n");
> >>          exit(1);
> >>      }
> >> diff --git a/hw/pci/msix.c b/hw/pci/msix.c
> >> index 24de260..9a1894f 100644
> >> --- a/hw/pci/msix.c
> >> +++ b/hw/pci/msix.c
> >> @@ -291,33 +291,29 @@ int msix_init(struct PCIDevice *dev, unsigned
> >>short nentries,
> >>  }
> >>     int msix_init_exclusive_bar(PCIDevice *dev, unsigned short
> >>nentries,
> >> -                            uint8_t bar_nr)
> >> +                            uint8_t bar_nr, uint32_t bar_size)
> >>  {
> >>      int ret;
> >>      char *name;
> >> +    uint32_t bar_pba_offset = bar_size / 2;
> >
> >Spec says we must give BIR 4k of it's own, but for
> >larger BARs, using up half the BAR just for BIR seems
> >wasteful.
> 
> I see, I will make PBA size more accurate.
> 
> >
> >
> >>      /*
> >>       * Migration compatibility dictates that this remains a 4k
> >>       * BAR with the vector table in the lower half and PBA in
> >>       * the upper half.  Do not use these elsewhere!
> >>       */
> >
> >You've left comment here where it no longer makes
> >any sense.
> 
> Will remove this.
> 
> >
> >
> >> -#define MSIX_EXCLUSIVE_BAR_SIZE 4096
> >> -#define MSIX_EXCLUSIVE_BAR_TABLE_OFFSET 0
> >> -#define MSIX_EXCLUSIVE_BAR_PBA_OFFSET (MSIX_EXCLUSIVE_BAR_SIZE / 2)
> >> -#define MSIX_EXCLUSIVE_CAP_OFFSET 0
> >> -
> >> -    if (nentries * PCI_MSIX_ENTRY_SIZE >
> >>MSIX_EXCLUSIVE_BAR_PBA_OFFSET) {
> >> +    if (nentries * PCI_MSIX_ENTRY_SIZE > bar_pba_offset) {
> >>          return -EINVAL;
> >>      }
> >>      name = g_strdup_printf("%s-msix", dev->name);
> >> -    memory_region_init(&dev->msix_exclusive_bar, OBJECT(dev), name,
> >>MSIX_EXCLUSIVE_BAR_SIZE);
> >> +    memory_region_init(&dev->msix_exclusive_bar, OBJECT(dev), name,
> >>bar_size);
> >>      g_free(name);
> >>         ret = msix_init(dev, nentries, &dev->msix_exclusive_bar,
> >>bar_nr,
> >> -                    MSIX_EXCLUSIVE_BAR_TABLE_OFFSET,
> >>&dev->msix_exclusive_bar,
> >> -                    bar_nr, MSIX_EXCLUSIVE_BAR_PBA_OFFSET,
> >> -                    MSIX_EXCLUSIVE_CAP_OFFSET);
> >> +                    0, &dev->msix_exclusive_bar,
> >> +                    bar_nr, bar_pba_offset,
> >> +                    0);
> >>      if (ret) {
> >>          return ret;
> >>      }
> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >> index 02e3ce8..4a5febb 100644
> >> --- a/hw/virtio/virtio-pci.c
> >> +++ b/hw/virtio/virtio-pci.c
> >> @@ -937,7 +937,7 @@ static void virtio_pci_device_plugged(DeviceState
> >>*d)
> >>      config[PCI_INTERRUPT_PIN] = 1;
> >>      if (proxy->nvectors &&
> >> -        msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors, 1))
> >>{
> >> +        msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors, 1,
> >>4096)) {
> >>          error_report("unable to init msix vectors to %" PRIu32,
> >>                       proxy->nvectors);
> >>          proxy->nvectors = 0;
> >> diff --git a/include/hw/pci/msix.h b/include/hw/pci/msix.h
> >> index 954d82b..43edebc 100644
> >> --- a/include/hw/pci/msix.h
> >> +++ b/include/hw/pci/msix.h
> >> @@ -11,7 +11,7 @@ int msix_init(PCIDevice *dev, unsigned short
> >>nentries,
> >>                unsigned table_offset, MemoryRegion *pba_bar,
> >>                uint8_t pba_bar_nr, unsigned pba_offset, uint8_t
> >>cap_pos);
> >>  int msix_init_exclusive_bar(PCIDevice *dev, unsigned short nentries,
> >> -                            uint8_t bar_nr);
> >> +                            uint8_t bar_nr, uint32_t bar_size);
> >>     void msix_write_config(PCIDevice *dev, uint32_t address, uint32_t
> >>val, int len);
> >>    --  2.1.0