hv_netvsc: Fix missed pagebuf entries in netvsc_dma_map/unmap()

netvsc_dma_map() and netvsc_dma_unmap() currently check the cp_partial
flag and adjust the page_count so that pagebuf entries for the RNDIS
portion of the message are skipped when it has already been copied into
a send buffer. But this adjustment has already been made by code in
netvsc_send(). The duplicate adjustment causes some pagebuf entries to
not be mapped. In a normal VM, this doesn't break anything because the
mapping doesn’t change the PFN. But in a Confidential VM,
dma_map_single() does bounce buffering and provides a different PFN.
Failing to do the mapping causes the wrong PFN to be passed to Hyper-V,
and various errors ensue.

Fix this by removing the duplicate adjustment in netvsc_dma_map() and
netvsc_dma_unmap().

Fixes: 846da38d ("net: netvsc: Add Isolation VM support for netvsc driver")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Link: https://lore.kernel.org/r/1675135986-254490-1-git-send-email-mikelley@microsoft.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/hyperv/netvsc.c

@@ -987,9 +987,6 @@ static void netvsc_copy_to_send_buf(struct netvsc_device *net_device,
 void netvsc_dma_unmap(struct hv_device *hv_dev,
 		      struct hv_netvsc_packet *packet)
 {
-	u32 page_count = packet->cp_partial ?
-		packet->page_buf_cnt - packet->rmsg_pgcnt :
-		packet->page_buf_cnt;
 	int i;
 
 	if (!hv_is_isolation_supported())
@@ -998,7 +995,7 @@ void netvsc_dma_unmap(struct hv_device *hv_dev,
 	if (!packet->dma_range)
 		return;
 
-	for (i = 0; i < page_count; i++)
+	for (i = 0; i < packet->page_buf_cnt; i++)
 		dma_unmap_single(&hv_dev->device, packet->dma_range[i].dma,
 				 packet->dma_range[i].mapping_size,
 				 DMA_TO_DEVICE);
@@ -1028,9 +1025,7 @@ static int netvsc_dma_map(struct hv_device *hv_dev,
 			  struct hv_netvsc_packet *packet,
 			  struct hv_page_buffer *pb)
 {
-	u32 page_count =  packet->cp_partial ?
-		packet->page_buf_cnt - packet->rmsg_pgcnt :
-		packet->page_buf_cnt;
+	u32 page_count = packet->page_buf_cnt;
 	dma_addr_t dma;
 	int i;