Re: [Qemu-devel] [PATCH v2 1/4] virtio-pci: add flags to enable/disable legacy/modern

[Fam Zheng]

On Mon, 02/16 17:33, Gerd Hoffmann wrote:
> Add VIRTIO_PCI_FLAG_DISABLE_LEGACY and VIRTIO_PCI_FLAG_DISABLE_MODERN
> for VirtIOPCIProxy->flags.  Also add properties for them.  They can be
> used to disable modern (virtio 1.0) or legacy (virtio 0.9) modes.  By
> default both are advertized and the guest driver can choose.
> 
> Signed-off-by: Gerd Hoffmann <address@hidden>
> ---
>  hw/virtio/virtio-pci.c | 46 +++++++++++++++++++++++++++++++++-------------
>  hw/virtio/virtio-pci.h |  6 ++++++
>  2 files changed, 39 insertions(+), 13 deletions(-)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 4c9a0b8..6c0c650 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1233,6 +1233,8 @@ static void virtio_pci_device_plugged(DeviceState *d)
>  {
>      VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
>      VirtioBusState *bus = &proxy->bus;
> +    bool legacy = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY);
> +    bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
>      uint8_t *config;
>      uint32_t size;
>  
> @@ -1240,13 +1242,24 @@ static void virtio_pci_device_plugged(DeviceState *d)
>      if (proxy->class_code) {
>          pci_config_set_class(config, proxy->class_code);
>      }
> -    pci_set_word(config + PCI_SUBSYSTEM_VENDOR_ID,
> -                 pci_get_word(config + PCI_VENDOR_ID));
> -    pci_set_word(config + PCI_SUBSYSTEM_ID, virtio_bus_get_vdev_id(bus));
> +
> +    if (legacy) {
> +        /* legacy and transitional */
> +        pci_set_word(config + PCI_SUBSYSTEM_VENDOR_ID,
> +                     pci_get_word(config + PCI_VENDOR_ID));
> +        pci_set_word(config + PCI_SUBSYSTEM_ID, virtio_bus_get_vdev_id(bus));
> +    } else {
> +        /* pure virtio-1.0 */
> +        pci_set_word(config + PCI_VENDOR_ID,
> +                     PCI_VENDOR_ID_REDHAT_QUMRANET);
> +        pci_set_word(config + PCI_DEVICE_ID,
> +                     0x1040 + virtio_bus_get_vdev_id(bus));
> +        pci_config_set_revision(config, 1);
> +    }

Should we forbid setting both legacy and modern at the same time?

Fam