Re: [PATCH v2 1/6] virtio/virtio-pci: Handle extra notification data

On 3/13/24 11:01 PM, Jason Wang wrote:
> On Wed, Mar 13, 2024 at 7:55 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: shadow_avail_idx
>>   - lower 16 bits: virtqueue index
>>
>> In a packed virtqueue layout, this data includes:
>>   - upper 16 bits: 1-bit wrap counter & 15-bit shadow_avail_idx
>>   - lower 16 bits: virtqueue index
>>
>> Tested-by: Lei Yang <[email protected]>
>> Reviewed-by: Eugenio Pérez <[email protected]>
>> Signed-off-by: Jonah Palmer <[email protected]>
>> ---
>>   hw/virtio/virtio-pci.c     | 10 +++++++---
>>   hw/virtio/virtio.c         | 18 ++++++++++++++++++
>>   include/hw/virtio/virtio.h |  1 +
>>   3 files changed, 26 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
>> index cb6940fc0e..0f5c3c3b2f 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 +408,12 @@ 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);
>> +        vq_idx = val;
>> +        if (vq_idx < VIRTIO_QUEUE_MAX) {
>> +            if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
>> +                virtio_queue_set_shadow_avail_data(vdev, val);
>> +            }
>> +            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..bcb9e09df0 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -2255,6 +2255,24 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
>>       }
>>   }
>>
>> +void virtio_queue_set_shadow_avail_data(VirtIODevice *vdev, uint32_t data)
>> +{
>> +    /* Lower 16 bits is the virtqueue index */
>> +    uint16_t i = data;
>> +    VirtQueue *vq = &vdev->vq[i];
>> +
>> +    if (!vq->vring.desc) {
>> +        return;
>> +    }
>> +
>> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
>> +        vq->shadow_avail_wrap_counter = (data >> 31) & 0x1;
>> +        vq->shadow_avail_idx = (data >> 16) & 0x7FFF;
>> +    } else {
>> +        vq->shadow_avail_idx = (data >> 16);
> 
> Do we need to do a sanity check for this value?
> 
> Thanks
> 

It can't hurt, right? What kind of check did you have in mind?

if (vq->shadow_avail_idx >= vq->vring.num)

Or something else?

>> +    }
>> +}
>> +
>>   static void virtio_queue_notify_vq(VirtQueue *vq)
>>   {
>>       if (vq->vring.desc && vq->handle_output) {
>> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
>> index c8f72850bc..53915947a7 100644
>> --- a/include/hw/virtio/virtio.h
>> +++ b/include/hw/virtio/virtio.h
>> @@ -335,6 +335,7 @@ void virtio_queue_update_rings(VirtIODevice *vdev, int n);
>>   void virtio_init_region_cache(VirtIODevice *vdev, int n);
>>   void virtio_queue_set_align(VirtIODevice *vdev, int n, int align);
>>   void virtio_queue_notify(VirtIODevice *vdev, int n);
>> +void virtio_queue_set_shadow_avail_data(VirtIODevice *vdev, uint32_t data);
>>   uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);
>>   void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector);
>>   int virtio_queue_set_host_notifier_mr(VirtIODevice *vdev, int n,
>> --
>> 2.39.3
>>
>