Re: [Qemu-devel] [PATCH 2/2] hw/virtio: group virtio flags into an enum

[Laurent Vivier <lvivier@redhat.com>]

On 10/02/2016 13:22, Marcel Apfelbaum wrote:
> Minimizes the possibility to assign
> the same bit to different features.
> 
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> ---
>  hw/virtio/virtio-pci.h | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index 6686b10..817bcde 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -58,6 +58,16 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
>  #define VIRTIO_PCI_BUS_CLASS(klass) \
>          OBJECT_CLASS_CHECK(VirtioPCIBusClass, klass, TYPE_VIRTIO_PCI_BUS)
>  
> +enum {
> +    VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT,
> +    VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT,
> +    VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT,
> +    VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT,
> +    VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT,
> +    VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT,
> +    VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT,
> +};

You can keep the "#define", doing something like this after the enum:

#define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT

So, if someone includes this ".h" out of qemu and wants to use some
"#ifdef" to see if the bit is defined, it always works.
(see for an example, /usr/include/linux/rtnetlink.h).

> +
>  /* Need to activate work-arounds for buggy guests at vmstate load. */
>  #define VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT  0

You should remove this one too.

>  #define VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION \
> @@ -65,23 +75,17 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
>  
>  /* Performance improves when virtqueue kick processing is decoupled from the
>   * 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)
>  
>  /* virtio version flags */
> -#define VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT 2
> -#define VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT 3
> -#define VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT 6
>  #define VIRTIO_PCI_FLAG_DISABLE_LEGACY (1 << VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT)
>  #define VIRTIO_PCI_FLAG_DISABLE_MODERN (1 << VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT)
>  #define VIRTIO_PCI_FLAG_DISABLE_PCIE (1 << VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT)
>  
>  /* migrate extra state */
> -#define VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT 4
>  #define VIRTIO_PCI_FLAG_MIGRATE_EXTRA (1 << VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT)
>  
>  /* have pio notification for modern device ? */
> -#define VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT 5
>  #define VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY \
>      (1 << VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT)
>  
>