Re: [Qemu-devel] [PATCH V4 19/19] virtio-pci: introduce auto_msix_bar_size property

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

On Thu, Mar 19, 2015 at 01:23:56PM +0800, Jason Wang wrote:
> 
> 
> On Wed, Mar 18, 2015 at 8:57 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> >On Wed, Mar 18, 2015 at 05:35:09PM +0800, Jason Wang wrote:
> >> Currently we don't support more than 128 MSI-X vectors for a pci
> >> devices, trying to use vector=129 for a virtio-net-pci device may get:
> >> qemu-system-x86_64: -device virtio-net-pci,netdev=hn0,vectors=129:
> >> unable to init msix vectors to 129
> >>   This this because the MSI-X bar size were hard-coded as 4096. So this
> >> patch introduces boolean auto_msix_bar_size property for
> >> virito-pci devices. Enable this will let the device calculate the msix
> >> bar size based on the number of MSI-X entries instead of previous 4096
> >> hard-coded limit.
> >> This is a must to let virtio-net can up to 256 queues and each queue
> >> were associated with a specific MSI-X entry.
> >> Cc: Paolo Bonzini <pbonzini@redhat.com>
> >> Cc: Richard Henderson <rth@twiddle.net>
> >> Cc: Michael S. Tsirkin <mst@redhat.com>
> >> Cc: Alexander Graf <agraf@suse.de>
> >> Cc: qemu-ppc@nongnu.org
> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >
> >I don't understand what this property does.
> >What if I *don't* set auto_msix_bar_size?
> >vectors<=128 works exactly like it dif previously, vectors=129 fails?
> >Does not seem like useful behaviour, to me.
> >
> >
> >> ---
> >>  hw/i386/pc_piix.c      |  8 ++++++++
> >>  hw/i386/pc_q35.c       |  8 ++++++++
> >>  hw/ppc/spapr.c         | 11 ++++++++++-
> >>  hw/virtio/virtio-pci.c | 17 +++++++++++++++--
> >>  hw/virtio/virtio-pci.h |  3 +++
> >>  include/hw/compat.h    | 11 +++++++++++
> >>  6 files changed, 55 insertions(+), 3 deletions(-)
> >> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> >> index 0796719..8808500 100644
> >> --- a/hw/i386/pc_piix.c
> >> +++ b/hw/i386/pc_piix.c
> >> @@ -552,6 +552,10 @@ static QEMUMachine pc_i440fx_machine_v2_3 = {
> >>      PC_I440FX_2_3_MACHINE_OPTIONS,
> >>      .name = "pc-i440fx-2.3",
> >>      .init = pc_init_pci_2_3,
> >> +    .compat_props = (GlobalProperty[]) {
> >> +        HW_COMPAT_2_3,
> >> +        { /* end of list */ }
> >> +    },
> >>  };
> >>  #define PC_I440FX_2_2_MACHINE_OPTIONS PC_I440FX_2_3_MACHINE_OPTIONS
> >> @@ -560,6 +564,10 @@ static QEMUMachine pc_i440fx_machine_v2_2 = {
> >>      PC_I440FX_2_2_MACHINE_OPTIONS,
> >>      .name = "pc-i440fx-2.2",
> >>      .init = pc_init_pci_2_2,
> >> +    .compat_props = (GlobalProperty[]) {
> >> +        HW_COMPAT_2_2,
> >> +        { /* end of list */ }
> >> +    },
> >>  };
> >>  #define PC_I440FX_2_1_MACHINE_OPTIONS                           \
> >> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> >> index a8a34a4..4a34349 100644
> >> --- a/hw/i386/pc_q35.c
> >> +++ b/hw/i386/pc_q35.c
> >> @@ -448,6 +448,10 @@ static QEMUMachine pc_q35_machine_v2_3 = {
> >>      PC_Q35_2_3_MACHINE_OPTIONS,
> >>      .name = "pc-q35-2.3",
> >>      .init = pc_q35_init_2_3,
> >> +    .compat_props = (GlobalProperty[]) {
> >> +        HW_COMPAT_2_3,
> >> +        { /* end of list */ }
> >> +    },
> >>  };
> >>  #define PC_Q35_2_2_MACHINE_OPTIONS PC_Q35_2_3_MACHINE_OPTIONS
> >> @@ -456,6 +460,10 @@ static QEMUMachine pc_q35_machine_v2_2 = {
> >>      PC_Q35_2_2_MACHINE_OPTIONS,
> >>      .name = "pc-q35-2.2",
> >>      .init = pc_q35_init_2_2,
> >> +    .compat_props = (GlobalProperty[]) {
> >> +        HW_COMPAT_2_2,
> >> +        { /* end of list */ }
> >> +    },
> >>  };
> >>  #define PC_Q35_2_1_MACHINE_OPTIONS                      \
> >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> >> index 5f25dd3..853a5cc 100644
> >> --- a/hw/ppc/spapr.c
> >> +++ b/hw/ppc/spapr.c
> >> @@ -1794,12 +1794,16 @@ static const TypeInfo spapr_machine_info = {
> >>      },
> >>  };
> >> +#define SPAPR_COMPAT_2_3 \
> >> +        HW_COMPAT_2_3
> >> +
> >>  #define SPAPR_COMPAT_2_2 \
> >> +        SPAPR_COMPAT_2_3, \
> >>          {\
> >>              .driver   = TYPE_SPAPR_PCI_HOST_BRIDGE,\
> >>              .property = "mem_win_size",\
> >>              .value    = "0x20000000",\
> >> -        }
> >> +        } \
> >>  #define SPAPR_COMPAT_2_1 \
> >>          SPAPR_COMPAT_2_2
> >> @@ -1883,10 +1887,15 @@ static const TypeInfo spapr_machine_2_2_info =
> >>{
> >>     static void spapr_machine_2_3_class_init(ObjectClass *oc, void
> >>*data)
> >>  {
> >> +    static GlobalProperty compat_props[] = {
> >> +        SPAPR_COMPAT_2_3,
> >> +        { /* end of list */ }
> >> +    };
> >>      MachineClass *mc = MACHINE_CLASS(oc);
> >>      mc->name = "pseries-2.3";
> >>      mc->desc = "pSeries Logical Partition (PAPR compliant) v2.3";
> >> +    mc->compat_props = compat_props;
> >>  }
> >>  static const TypeInfo spapr_machine_2_3_info = {
> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >> index 4a5febb..f4cd405 100644
> >> --- a/hw/virtio/virtio-pci.c
> >> +++ b/hw/virtio/virtio-pci.c
> >> @@ -925,7 +925,7 @@ static void virtio_pci_device_plugged(DeviceState
> >>*d)
> >>      VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
> >>      VirtioBusState *bus = &proxy->bus;
> >>      uint8_t *config;
> >> -    uint32_t size;
> >> +    uint32_t size, bar_size;
> >>      config = proxy->pci_dev.config;
> >>      if (proxy->class_code) {
> >> @@ -936,8 +936,19 @@ static void virtio_pci_device_plugged(DeviceState
> >>*d)
> >>      pci_set_word(config + PCI_SUBSYSTEM_ID,
> >>virtio_bus_get_vdev_id(bus));
> >>      config[PCI_INTERRUPT_PIN] = 1;
> >> +    if (proxy->flags & VIRTIO_PCI_FLAG_AUTO_MSIX_SIZE) {
> >> +        bar_size = proxy->nvectors * PCI_MSIX_ENTRY_SIZE * 2;
> >> +        if (bar_size & (bar_size - 1)) {
> >> +            bar_size = 1 << qemu_fls(bar_size);
> >> +        }
> >> +    } else {
> >> +        /* For migration compatibility */
> >> +        bar_size = 4096;
> >> +    }
> >> +
> >>      if (proxy->nvectors &&
> >> -        msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors, 1,
> >>4096)) {
> >> +        msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors, 1,
> >> +                                bar_size)) {
> >>          error_report("unable to init msix vectors to %" PRIu32,
> >>                       proxy->nvectors);
> >>          proxy->nvectors = 0;
> >
> >
> >As I expected, msix format stuff spreads out to virtio.
> >Consider "vectors * PCI_MSIX_ENTRY_SIZE * 2"
> >That's because you use half the BAR for BIR in msix.c
> >So any change will have to be done in two places,
> >that's bad.
> 
> Yes, will move to msix.c by passing the compat flags to
> msix_init_exclusive_bar().

I really wonder why isn't just specifying # of vectors enough.


> >
> >
> >> @@ -1370,6 +1381,8 @@ static const TypeInfo virtio_serial_pci_info = {
> >>  static Property virtio_net_properties[] = {
> >>      DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
> >>                      VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, false),
> >> +    DEFINE_PROP_BIT("auto_msix_bar_size", VirtIOPCIProxy, flags,
> >> +                    VIRTIO_PCI_FLAG_AUTO_MSIX_SIZE_BIT, true),
> >>      DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 3),
> >>      DEFINE_VIRTIO_NET_FEATURES(VirtIOPCIProxy, host_features),
> >>      DEFINE_PROP_END_OF_LIST(),
> >> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> >> index 3bac016..82a6782 100644
> >> --- a/hw/virtio/virtio-pci.h
> >> +++ b/hw/virtio/virtio-pci.h
> >> @@ -62,6 +62,9 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
> >>   * vcpu thread using ioeventfd for some devices. */
> >>  #define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT 1
> >>  #define VIRTIO_PCI_FLAG_USE_IOEVENTFD   (1 <<
> >>VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT)
> >> +#define VIRTIO_PCI_FLAG_AUTO_MSIX_SIZE_BIT 2
> >> +#define VIRTIO_PCI_FLAG_AUTO_MSIX_SIZE \
> >> +    (1 << VIRTIO_PCI_FLAG_AUTO_MSIX_SIZE_BIT)
> >>  typedef struct {
> >>      MSIMessage msg;
> >> diff --git a/include/hw/compat.h b/include/hw/compat.h
> >> index 313682a..3186275 100644
> >> --- a/include/hw/compat.h
> >> +++ b/include/hw/compat.h
> >> @@ -1,7 +1,18 @@
> >>  #ifndef HW_COMPAT_H
> >>  #define HW_COMPAT_H
> >> +#define HW_COMPAT_2_3 \
> >> +        {\
> >> +            .driver   = "virtio-net-pci",\
> >> +            .property = "auto_msix_bar_size",\
> >> +            .value    = "off",\
> >> +        }
> >> +
> >> +#define HW_COMPAT_2_2 \
> >> +        HW_COMPAT_2_3
> >> +
> >>  #define HW_COMPAT_2_1 \
> >> +        HW_COMPAT_2_2, \
> >>          {\
> >>              .driver   = "intel-hda",\
> >>              .property = "old_msi_addr",\
> >> --  2.1.0