RE: [PATCH 3/6] Drivers: hv: vmbus: Introduce vmbus_sendpacket_getid()

[Michael Kelley (LINUX)]

From: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> Sent: Wednesday, April 6, 2022 9:30 PM
> 
> The function can be used to send a VMbus packet and retrieve the
> corresponding transaction ID.  It will be used by hv_pci.
> 
> No functional change.
> 
> Suggested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> ---
>  drivers/hv/channel.c      | 38 ++++++++++++++++++++++++++++++++------
>  drivers/hv/hyperv_vmbus.h |  2 +-
>  drivers/hv/ring_buffer.c  | 14 +++++++++++---
>  include/linux/hyperv.h    |  7 +++++++
>  4 files changed, 51 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 20fc8d50a0398..585a8084848bf 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -1022,11 +1022,13 @@ void vmbus_close(struct vmbus_channel *channel)
>  EXPORT_SYMBOL_GPL(vmbus_close);
> 
>  /**
> - * vmbus_sendpacket() - Send the specified buffer on the given channel
> + * vmbus_sendpacket_getid() - Send the specified buffer on the given channel
>   * @channel: Pointer to vmbus_channel structure
>   * @buffer: Pointer to the buffer you want to send the data from.
>   * @bufferlen: Maximum size of what the buffer holds.
>   * @requestid: Identifier of the request
> + * @trans_id: Identifier of the transaction associated to this request, if
> + *            the send is successful; undefined, otherwise.
>   * @type: Type of packet that is being sent e.g. negotiate, time
>   *	  packet etc.
>   * @flags: 0 or VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED
> @@ -1036,8 +1038,8 @@ EXPORT_SYMBOL_GPL(vmbus_close);
>   *
>   * Mainly used by Hyper-V drivers.
>   */
> -int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
> -			   u32 bufferlen, u64 requestid,
> +int vmbus_sendpacket_getid(struct vmbus_channel *channel, void *buffer,
> +			   u32 bufferlen, u64 requestid, u64 *trans_id,
>  			   enum vmbus_packet_type type, u32 flags)
>  {
>  	struct vmpacket_descriptor desc;
> @@ -1063,7 +1065,31 @@ int vmbus_sendpacket(struct vmbus_channel *channel,
> void *buffer,
>  	bufferlist[2].iov_base = &aligned_data;
>  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
> 
> -	return hv_ringbuffer_write(channel, bufferlist, num_vecs, requestid);
> +	return hv_ringbuffer_write(channel, bufferlist, num_vecs, requestid, trans_id);
> +}
> +EXPORT_SYMBOL(vmbus_sendpacket_getid);
> +
> +/**
> + * vmbus_sendpacket() - Send the specified buffer on the given channel
> + * @channel: Pointer to vmbus_channel structure
> + * @buffer: Pointer to the buffer you want to send the data from.
> + * @bufferlen: Maximum size of what the buffer holds.
> + * @requestid: Identifier of the request
> + * @type: Type of packet that is being sent e.g. negotiate, time
> + *	  packet etc.
> + * @flags: 0 or VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED
> + *
> + * Sends data in @buffer directly to Hyper-V via the vmbus.
> + * This will send the data unparsed to Hyper-V.
> + *
> + * Mainly used by Hyper-V drivers.
> + */
> +int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
> +		     u32 bufferlen, u64 requestid,
> +		     enum vmbus_packet_type type, u32 flags)
> +{
> +	return vmbus_sendpacket_getid(channel, buffer, bufferlen,
> +				      requestid, NULL, type, flags);
>  }
>  EXPORT_SYMBOL(vmbus_sendpacket);
> 
> @@ -1122,7 +1148,7 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel
> *channel,
>  	bufferlist[2].iov_base = &aligned_data;
>  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
> 
> -	return hv_ringbuffer_write(channel, bufferlist, 3, requestid);
> +	return hv_ringbuffer_write(channel, bufferlist, 3, requestid, NULL);
>  }
>  EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer);
> 
> @@ -1160,7 +1186,7 @@ int vmbus_sendpacket_mpb_desc(struct vmbus_channel
> *channel,
>  	bufferlist[2].iov_base = &aligned_data;
>  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
> 
> -	return hv_ringbuffer_write(channel, bufferlist, 3, requestid);
> +	return hv_ringbuffer_write(channel, bufferlist, 3, requestid, NULL);
>  }
>  EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);
> 
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 3a1f007b678a0..64c0b9cbe183b 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -181,7 +181,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info
> *ring_info);
> 
>  int hv_ringbuffer_write(struct vmbus_channel *channel,
>  			const struct kvec *kv_list, u32 kv_count,
> -			u64 requestid);
> +			u64 requestid, u64 *trans_id);
> 
>  int hv_ringbuffer_read(struct vmbus_channel *channel,
>  		       void *buffer, u32 buflen, u32 *buffer_actual_len,
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 3d215d9dec433..e101b11f95e5d 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -283,7 +283,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info
> *ring_info)
>  /* Write to the ring buffer. */
>  int hv_ringbuffer_write(struct vmbus_channel *channel,
>  			const struct kvec *kv_list, u32 kv_count,
> -			u64 requestid)
> +			u64 requestid, u64 *trans_id)
>  {
>  	int i;
>  	u32 bytes_avail_towrite;
> @@ -294,7 +294,7 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
>  	unsigned long flags;
>  	struct hv_ring_buffer_info *outring_info = &channel->outbound;
>  	struct vmpacket_descriptor *desc = kv_list[0].iov_base;
> -	u64 rqst_id = VMBUS_NO_RQSTOR;
> +	u64 __trans_id, rqst_id = VMBUS_NO_RQSTOR;
> 
>  	if (channel->rescind)
>  		return -ENODEV;
> @@ -353,7 +353,15 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
>  		}
>  	}
>  	desc = hv_get_ring_buffer(outring_info) + old_write;
> -	desc->trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id;
> +	__trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id;
> +	/*
> +	 * Ensure the compiler doesn't generate code that reads the value of
> +	 * the transaction ID from the ring buffer, which is shared with the
> +	 * Hyper-V host and subject to being changed at any time.
> +	 */
> +	WRITE_ONCE(desc->trans_id, __trans_id);
> +	if (trans_id)
> +		*trans_id = __trans_id;
> 
>  	/* Set previous packet start */
>  	prev_indices = hv_get_ring_bufferindices(outring_info);
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index fe2e0179ed51e..a7cb596d893b1 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1161,6 +1161,13 @@ extern int vmbus_open(struct vmbus_channel *channel,
> 
>  extern void vmbus_close(struct vmbus_channel *channel);
> 
> +extern int vmbus_sendpacket_getid(struct vmbus_channel *channel,
> +				  void *buffer,
> +				  u32 bufferLen,
> +				  u64 requestid,
> +				  u64 *trans_id,
> +				  enum vmbus_packet_type type,
> +				  u32 flags);
>  extern int vmbus_sendpacket(struct vmbus_channel *channel,
>  				  void *buffer,
>  				  u32 bufferLen,
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>