"K. Y. Srinivasan" <kys@xxxxxxxxxxxxx> writes:
> Implement copy-free read APIs.
>
> Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> ---
> drivers/hv/ring_buffer.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/hyperv.h | 6 +++++
> 2 files changed, 61 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index c2c2b2e..c80e1f3 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -444,3 +444,58 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
>
> return ret;
> }
> +
> +/*
> + * In-place read functions.
> + */
> +bool get_next_pkt_raw(struct vmbus_channel *channel,
> + struct vmpacket_descriptor **desc)
I suggest we make these functions return pointers and use
ERR_PTR()/IS_ERR() when we need to return an error.
> +{
> + struct hv_ring_buffer_info *ring_info = &channel->inbound;
> + u32 read_loc = ring_info->ring_buffer->read_index;
> + void *ring_buffer = hv_get_ring_buffer(ring_info);
> + struct vmpacket_descriptor *cur_desc;
> + u32 packetlen;
> + u32 dsize = ring_info->ring_datasize;
> + u32 bytes_avail_toread = hv_get_bytes_to_read(ring_info);
> +
> + if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
> + return false;
> +
> + if ((read_loc + sizeof(*desc)) > dsize)
> + return false;
> +
> + cur_desc = ring_buffer + read_loc;
> + packetlen = cur_desc->len8 << 3;
> +
> + if ((read_loc + packetlen + 8) > (dsize - 1))
Could you please add a define for this '8'?
> + return false;
> +
> + *desc = cur_desc;
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(get_next_pkt_raw);
> +
> +void put_pkt_raw(struct vmbus_channel *channel,
> + struct vmpacket_descriptor *desc)
> +{
> + struct hv_ring_buffer_info *ring_info = &channel->inbound;
> + u32 read_loc = ring_info->ring_buffer->read_index;
> + u32 packetlen = desc->len8 << 3;
> + u32 dsize = ring_info->ring_datasize;
> +
> + if ((read_loc + packetlen + 8) > dsize)
> + BUG();
> +
> + /*
> + * Make sure all reads are done before we update the read index since
> + * the writer may start writing to the read area once the read index
> + * is updated.
> + */
> + virt_mb();
> + ring_info->ring_buffer->read_index += packetlen + 8;
> +
> + if (hv_need_to_signal_on_read(ring_info))
> + vmbus_set_event(channel);
> +}
> +EXPORT_SYMBOL_GPL(put_pkt_raw);
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index a6b053c..455f3f0 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1035,6 +1035,12 @@ extern int vmbus_recvpacket_raw(struct vmbus_channel *channel,
> u32 *buffer_actual_len,
> u64 *requestid);
>
> +bool get_next_pkt_raw(struct vmbus_channel *channel,
> + struct vmpacket_descriptor **desc);
> +
> +void put_pkt_raw(struct vmbus_channel *channel,
> + struct vmpacket_descriptor *desc);
> +
>
> extern void vmbus_ontimer(unsigned long data);
--
Vitaly
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