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

Andrea Parri (Microsoft)
2022-04-07T04:32:41Z

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@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
---
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