Drivers: hv: vmbus: Cleanup the packet send path

The current channel code is using scatterlist abstraction to pass data to the
ringbuffer API on the send path. This causes unnecessary translations
between virtual and physical addresses. Fix this.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 23 insertions, 19 deletions

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 69ea36f07b4d..602ca86a6488 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/hyperv.h>
+#include <linux/uio.h>
 
 #include "hyperv_vmbus.h"
 
@@ -554,14 +555,14 @@ EXPORT_SYMBOL_GPL(vmbus_close);
  *
  * Mainly used by Hyper-V drivers.
  */
-int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer,
+int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
 			   u32 bufferlen, u64 requestid,
 			   enum vmbus_packet_type type, u32 flags)
 {
 	struct vmpacket_descriptor desc;
 	u32 packetlen = sizeof(struct vmpacket_descriptor) + bufferlen;
 	u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));
-	struct scatterlist bufferlist[3];
+	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
 	int ret;
 	bool signal = false;
@@ -575,11 +576,12 @@ int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer,
 	desc.len8 = (u16)(packetlen_aligned >> 3);
 	desc.trans_id = requestid;
 
-	sg_init_table(bufferlist, 3);
-	sg_set_buf(&bufferlist[0], &desc, sizeof(struct vmpacket_descriptor));
-	sg_set_buf(&bufferlist[1], buffer, bufferlen);
-	sg_set_buf(&bufferlist[2], &aligned_data,
-		   packetlen_aligned - packetlen);
+	bufferlist[0].iov_base = &desc;
+	bufferlist[0].iov_len = sizeof(struct vmpacket_descriptor);
+	bufferlist[1].iov_base = buffer;
+	bufferlist[1].iov_len = bufferlen;
+	bufferlist[2].iov_base = &aligned_data;
+	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
 
@@ -605,7 +607,7 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
 	u32 descsize;
 	u32 packetlen;
 	u32 packetlen_aligned;
-	struct scatterlist bufferlist[3];
+	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
 	bool signal = false;
 
@@ -637,11 +639,12 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
 		desc.range[i].pfn	 = pagebuffers[i].pfn;
 	}
 
-	sg_init_table(bufferlist, 3);
-	sg_set_buf(&bufferlist[0], &desc, descsize);
-	sg_set_buf(&bufferlist[1], buffer, bufferlen);
-	sg_set_buf(&bufferlist[2], &aligned_data,
-		packetlen_aligned - packetlen);
+	bufferlist[0].iov_base = &desc;
+	bufferlist[0].iov_len = descsize;
+	bufferlist[1].iov_base = buffer;
+	bufferlist[1].iov_len = bufferlen;
+	bufferlist[2].iov_base = &aligned_data;
+	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
 
@@ -665,7 +668,7 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel,
 	u32 descsize;
 	u32 packetlen;
 	u32 packetlen_aligned;
-	struct scatterlist bufferlist[3];
+	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
 	bool signal = false;
 	u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset,
@@ -700,11 +703,12 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel,
 	memcpy(desc.range.pfn_array, multi_pagebuffer->pfn_array,
 	       pfncount * sizeof(u64));
 
-	sg_init_table(bufferlist, 3);
-	sg_set_buf(&bufferlist[0], &desc, descsize);
-	sg_set_buf(&bufferlist[1], buffer, bufferlen);
-	sg_set_buf(&bufferlist[2], &aligned_data,
-		packetlen_aligned - packetlen);
+	bufferlist[0].iov_base = &desc;
+	bufferlist[0].iov_len = descsize;
+	bufferlist[1].iov_base = buffer;
+	bufferlist[1].iov_len = bufferlen;
+	bufferlist[2].iov_base = &aligned_data;
+	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);