* Stefan Hajnoczi (stefa...@redhat.com) wrote: > The packed virtqueue layout was introduced in VIRTIO 1.1. It is a single > ring instead of a split avail/used ring design. There are CPU cache > advantages to this layout and it is also suited better to hardware > implementation. > > The vhost-net backend has already supported packed virtqueues for some > time. Performance benchmarks show that virtio-blk performance on NVMe > drives is also improved. > > Go ahead and enable this feature for all VIRTIO devices. Keep it > disabled for QEMU 5.0 and earlier machine types. > > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > --- > include/hw/virtio/virtio.h | 2 +- > hw/core/machine.c | 18 +++++++++++++++++- > 2 files changed, 18 insertions(+), 2 deletions(-) > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > index b69d517496..fd5b4a2044 100644 > --- a/include/hw/virtio/virtio.h > +++ b/include/hw/virtio/virtio.h > @@ -292,7 +292,7 @@ typedef struct VirtIORNGConf VirtIORNGConf; > DEFINE_PROP_BIT64("iommu_platform", _state, _field, \ > VIRTIO_F_IOMMU_PLATFORM, false), \ > DEFINE_PROP_BIT64("packed", _state, _field, \ > - VIRTIO_F_RING_PACKED, false) > + VIRTIO_F_RING_PACKED, true) > > hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n); > bool virtio_queue_enabled(VirtIODevice *vdev, int n); > diff --git a/hw/core/machine.c b/hw/core/machine.c > index bb3a7b18b1..3598c3c825 100644 > --- a/hw/core/machine.c > +++ b/hw/core/machine.c > @@ -28,7 +28,23 @@ > #include "hw/mem/nvdimm.h" > #include "migration/vmstate.h" > > -GlobalProperty hw_compat_5_0[] = {}; > +GlobalProperty hw_compat_5_0[] = { > + { "vhost-user-blk", "packed", "off" }, > + { "vhost-user-fs-device", "packed", "off" }, > + { "vhost-vsock-device", "packed", "off" }, > + { "virtio-9p-device", "packed", "off" }, > + { "virtio-balloon-device", "packed", "off" }, > + { "virtio-blk-device", "packed", "off" }, > + { "virtio-crypto-device", "packed", "off" }, > + { "virtio-gpu-device", "packed", "off" }, > + { "virtio-input-device", "packed", "off" }, > + { "virtio-iommu-device", "packed", "off" }, > + { "virtio-net-device", "packed", "off" }, > + { "virtio-pmem", "packed", "off" }, > + { "virtio-rng-device", "packed", "off" }, > + { "virtio-scsi-common", "packed", "off" }, > + { "virtio-serial-device", "packed", "off" }, > +}; > const size_t hw_compat_5_0_len = G_N_ELEMENTS(hw_compat_5_0); > > GlobalProperty hw_compat_4_2[] = { > -- > 2.25.3 > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK