Re: [RFC 1/8] virtio/virtio-pci: Handle extra notification data

On 3/1/24 2:55 PM, Eugenio Perez Martin wrote:
> On Fri, Mar 1, 2024 at 2:44 PM Jonah Palmer <[email protected]> wrote:
>>
>> Add support to virtio-pci devices for handling the extra data sent
>> from the driver to the device when the VIRTIO_F_NOTIFICATION_DATA
>> transport feature has been negotiated.
>>
>> The extra data that's passed to the virtio-pci device when this
>> feature is enabled varies depending on the device's virtqueue
>> layout.
>>
>> In a split virtqueue layout, this data includes:
>>   - upper 16 bits: last_avail_idx
>>   - lower 16 bits: virtqueue index
>>
>> In a packed virtqueue layout, this data includes:
>>   - upper 16 bits: 1-bit wrap counter & 15-bit last_avail_idx
>>   - lower 16 bits: virtqueue index
>>
>> Signed-off-by: Jonah Palmer <[email protected]>
>> ---
>>   hw/virtio/virtio-pci.c     | 13 ++++++++++---
>>   hw/virtio/virtio.c         | 13 +++++++++++++
>>   include/hw/virtio/virtio.h |  1 +
>>   3 files changed, 24 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
>> index 1a7039fb0c..c7c577b177 100644
>> --- a/hw/virtio/virtio-pci.c
>> +++ b/hw/virtio/virtio-pci.c
>> @@ -384,7 +384,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
>>   {
>>       VirtIOPCIProxy *proxy = opaque;
>>       VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>> -    uint16_t vector;
>> +    uint16_t vector, vq_idx;
>>       hwaddr pa;
>>
>>       switch (addr) {
>> @@ -408,8 +408,15 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
>>               vdev->queue_sel = val;
>>           break;
>>       case VIRTIO_PCI_QUEUE_NOTIFY:
>> -        if (val < VIRTIO_QUEUE_MAX) {
>> -            virtio_queue_notify(vdev, val);
>> +        if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
>> +            vq_idx = val & 0xFFFF;
>> +            virtio_set_notification_data(vdev, vq_idx, val);
>> +        } else {
>> +            vq_idx = val;
>> +        }
>> +
>> +        if (vq_idx < VIRTIO_QUEUE_MAX) {
>> +            virtio_queue_notify(vdev, vq_idx);
>>           }
>>           break;
>>       case VIRTIO_PCI_STATUS:
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index d229755eae..a61f69b7fd 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -2052,6 +2052,19 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
>>       return 0;
>>   }
>>
>> +void virtio_set_notification_data(VirtIODevice *vdev, uint16_t i, uint32_t data)
>> +{
>> +    VirtQueue *vq = &vdev->vq[i];
> 
> Sorry I sent the previous mail too fast :).
> 
> i should also be checked against VIRTIO_QUEUE_MAX and vq->vring.desc
> before continuing this function. Otherwise is an out of bound access.

Missed this, thank you. I will add these checks in!

> 
>> +
>> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
>> +        vq->last_avail_wrap_counter = (data >> 31) & 0x1;
>> +        vq->last_avail_idx = (data >> 16) & 0x7FFF;
>> +    } else {
>> +        vq->last_avail_idx = (data >> 16) & 0xFFFF;
>> +    }
>> +    vq->shadow_avail_idx = vq->last_avail_idx;
>> +}
>> +
>>   static enum virtio_device_endian virtio_default_endian(void)
>>   {
>>       if (target_words_bigendian()) {
>> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
>> index c8f72850bc..c92d8afc42 100644
>> --- a/include/hw/virtio/virtio.h
>> +++ b/include/hw/virtio/virtio.h
>> @@ -345,6 +345,7 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index);
>>   void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
>>   void virtio_update_irq(VirtIODevice *vdev);
>>   int virtio_set_features(VirtIODevice *vdev, uint64_t val);
>> +void virtio_set_notification_data(VirtIODevice *vdev, uint16_t i, uint32_t data);
>>
>>   /* Base devices.  */
>>   typedef struct VirtIOBlkConf VirtIOBlkConf;
>> --
>> 2.39.3
>>
>