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

From: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
To: Laurent Vivier <lvivier@redhat.com>,
	Marcel Apfelbaum <marcel@redhat.com>,
	qemu-devel@nongnu.org
Cc: jasowang@redhat.com, qemu-stable@nongnu.org, mst@redhat.com
Subject: Re: [Qemu-devel] [PATCH 2/2] hw/virtio: group virtio flags into an enum
Date: Wed, 10 Feb 2016 15:24:13 +0200	[thread overview]
Message-ID: <56BB39FD.5000000@gmail.com> (raw)
In-Reply-To: <56BB361B.6030705@redhat.com>

On 02/10/2016 03:07 PM, Laurent Vivier wrote:
>
>
> 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).

Thanks for the idea, but I don't think anyone would want to use those out
of qemu :)
I am also afraid that developers will forget to add it to the enum
and will still use the defines only.

>
>> +
>>   /* 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.

How did I manage to miss it? Thanks!
I'll send a v2
Marcel

>
>>   #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)
>>
>>
>
>