[PATCH V5 4/9] Drivers: hv: ring_buffer: enhance hv_ringbuffer_read() to support hvsock

[Dexuan Cui]

To get the payload of hvsock, we need raw=0 to skip the level-1 header
(i.e., struct vmpacket_descriptor desc) and we also need to skip the
level-2 header (i.e., struct vmpipe_proto_header pipe_hdr).

NB: if the length of the hvsock payload is not aligned with the 8-byte
boundeary, at most 7 padding bytes are appended, so the real hvsock
payload's length must be retrieved by the pipe_hdr.data_size field.

I 'upgrade' the 'raw' parameter of hv_ringbuffer_read() to a
'read_flags', trying to share the logic of the function.

This patch is required by the next patch, which will introduce the hvsock
send/recv APIs.

Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 drivers/hv/channel.c      | 10 +++++----
 drivers/hv/hyperv_vmbus.h | 13 +++++++++++-
 drivers/hv/ring_buffer.c  | 54 ++++++++++++++++++++++++++++++++++++-----------
 include/linux/hyperv.h    | 12 +++++++++++
 4 files changed, 72 insertions(+), 17 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index eaaa066..cc49966 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -940,13 +940,14 @@ EXPORT_SYMBOL_GPL(vmbus_sendpacket_multipagebuffer);
 static inline int
 __vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
 		   u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,
-		   bool raw)
+		   u32 read_flags)
 {
 	int ret;
 	bool signal = false;
 
 	ret = hv_ringbuffer_read(&channel->inbound, buffer, bufferlen,
-				 buffer_actual_len, requestid, &signal, raw);
+				 buffer_actual_len, requestid, &signal,
+				 read_flags);
 
 	if (signal)
 		vmbus_setevent(channel);
@@ -959,7 +960,7 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
 		     u64 *requestid)
 {
 	return __vmbus_recvpacket(channel, buffer, bufferlen,
-				  buffer_actual_len, requestid, false);
+				  buffer_actual_len, requestid, 0);
 }
 EXPORT_SYMBOL(vmbus_recvpacket);
 
@@ -971,6 +972,7 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
 			      u64 *requestid)
 {
 	return __vmbus_recvpacket(channel, buffer, bufferlen,
-				  buffer_actual_len, requestid, true);
+				  buffer_actual_len, requestid,
+				  HV_RINGBUFFER_READ_FLAG_RAW);
 }
 EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 0411b7b..46206b6 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -619,9 +619,20 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *ring_info,
 		    struct kvec *kv_list,
 		    u32 kv_count, bool *signal);
 
+/*
+ * By default, a read_flags of 0 means: the payload offset is
+ * sizeof(struct vmpacket_descriptor).
+ *
+ * If HV_RINGBUFFER_READ_FLAG_RAW is used, the payload offset is 0.
+ *
+ * If HV_RINGBUFFER_READ_FLAG_HVSOCK is used, the payload offset is
+ * sizeof(struct vmpacket_descriptor) + sizeof(struct vmpipe_proto_header).
+ */
+#define HV_RINGBUFFER_READ_FLAG_RAW		(1 << 0)
+#define HV_RINGBUFFER_READ_FLAG_HVSOCK		(1 << 1)
 int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 		       void *buffer, u32 buflen, u32 *buffer_actual_len,
-		       u64 *requestid, bool *signal, bool raw);
+		       u64 *requestid, bool *signal, u32 read_flags);
 
 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 			    struct hv_ring_buffer_debug_info *debug_info);
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index b53702c..03a509c 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -382,32 +382,43 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 
 int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 		       void *buffer, u32 buflen, u32 *buffer_actual_len,
-		       u64 *requestid, bool *signal, bool raw)
+		       u64 *requestid, bool *signal, u32 read_flags)
 {
+	bool raw = !!(read_flags & HV_RINGBUFFER_READ_FLAG_RAW);
+	bool hvsock = !!(read_flags & HV_RINGBUFFER_READ_FLAG_HVSOCK);
+
 	u32 bytes_avail_towrite;
 	u32 bytes_avail_toread;
 	u32 next_read_location = 0;
 	u64 prev_indices = 0;
 	unsigned long flags;
-	struct vmpacket_descriptor desc;
+	struct vmpipe_proto_header *pipe_hdr;
+	struct vmpacket_descriptor *desc;
 	u32 offset;
-	u32 packetlen;
+	u32 packetlen, tot_hdrlen;
 	int ret = 0;
 
 	if (buflen <= 0)
 		return -EINVAL;
 
+	tot_hdrlen = sizeof(*desc);
+	if (hvsock)
+		tot_hdrlen += sizeof(*pipe_hdr);
+
 	spin_lock_irqsave(&inring_info->ring_lock, flags);
 
 	*buffer_actual_len = 0;
-	*requestid = 0;
+
+	/* If some driver doesn't need the info, a NULL is passed in. */
+	if (requestid)
+		*requestid = 0;
 
 	hv_get_ringbuffer_availbytes(inring_info,
 				&bytes_avail_toread,
 				&bytes_avail_towrite);
 
 	/* Make sure there is something to read */
-	if (bytes_avail_toread < sizeof(desc)) {
+	if (bytes_avail_toread < tot_hdrlen) {
 		/*
 		 * No error is set when there is even no header, drivers are
 		 * supposed to analyze buffer_actual_len.
@@ -415,17 +426,26 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 		goto out_unlock;
 	}
 
+	if (tot_hdrlen > buflen) {
+		ret = -ENOBUFS;
+		goto out_unlock;
+	}
+
+	desc = (struct vmpacket_descriptor *)buffer;
+
 	next_read_location = hv_get_next_read_location(inring_info);
-	next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
-						    sizeof(desc),
+	next_read_location = hv_copyfrom_ringbuffer(inring_info, desc,
+						    tot_hdrlen,
 						    next_read_location);
+	offset = 0;
+	if (!raw)
+		offset += (desc->offset8 << 3);
+	if (hvsock)
+		offset += sizeof(*pipe_hdr);
 
-	offset = raw ? 0 : (desc.offset8 << 3);
-	packetlen = (desc.len8 << 3) - offset;
-	*buffer_actual_len = packetlen;
-	*requestid = desc.trans_id;
+	packetlen = (desc->len8 << 3) - offset;
 
-	if (bytes_avail_toread < packetlen + offset) {
+	if (bytes_avail_toread < (desc->len8 << 3)) {
 		ret = -EAGAIN;
 		goto out_unlock;
 	}
@@ -435,6 +455,16 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 		goto out_unlock;
 	}
 
+	if (requestid)
+		*requestid = desc->trans_id;
+
+	if (!hvsock)
+		*buffer_actual_len = packetlen;
+	else {
+		pipe_hdr = (struct vmpipe_proto_header *)(desc + 1);
+		*buffer_actual_len = pipe_hdr->data_size;
+	}
+
 	next_read_location =
 		hv_get_next_readlocation_withoffset(inring_info, offset);
 
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index b835d80..e005223 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1268,4 +1268,16 @@ extern __u32 vmbus_proto_version;
 
 int vmbus_send_tl_connect_request(const uuid_le *shv_guest_servie_id,
 				  const uuid_le *shv_host_servie_id);
+struct vmpipe_proto_header {
+	u32 pkt_type;
+
+	union {
+		u32 data_size;
+		struct {
+			u16 data_size;
+			u16 offset;
+		} partial;
+	};
+} __packed;
+
 #endif /* _HYPERV_H */
-- 
2.1.4

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