[PATCH net 1/1] hv_netvsc: Fix missed pagebuf entries in netvsc_dma_map/unmap()

[Michael Kelley]

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: 846da38de0e8 ("net: netvsc: Add Isolation VM support for netvsc driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
 drivers/net/hyperv/netvsc.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 661bbe6..8acfa40 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -949,9 +949,6 @@ 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())
@@ -960,7 +957,7 @@ 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);
@@ -990,9 +987,7 @@ 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;
 
-- 
1.8.3.1