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authorMichael Brown2017-05-19 03:50:21 +0200
committerMichael Brown2017-05-19 03:56:53 +0200
commit7457bfc5b29cee677ab9a49efcea4a476a648a1a (patch)
tree23148bddb4899aecadbe0ce2d9d5089fb1981d7b /src/drivers/net
parent[iscsi] Fix iBFT when no explicit initiator name setting exists (diff)
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[xen] Provide 18 4kB receive buffers to work around xen-netback bug
The Xen network backend (xen-netback) suffered from a regression between upstream Linux kernels 3.18 and 4.2 inclusive, which would cause packet reception to fail unless at least 18 receive buffers were available. This bug was fixed in kernel commit 1d5d485 ("xen-netback: require fewer guest Rx slots when not using GSO"). Work around this bug in affected versions of xen-netback by providing the requisite 18 receive buffers. Reported-by: Taylor Schneider <tschneider@live.com> Tested-by: Taylor Schneider <tschneider@live.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Diffstat (limited to 'src/drivers/net')
-rw-r--r--src/drivers/net/netfront.c19
-rw-r--r--src/drivers/net/netfront.h37
2 files changed, 41 insertions, 15 deletions
diff --git a/src/drivers/net/netfront.c b/src/drivers/net/netfront.c
index 2f4bbf2a..b6205542 100644
--- a/src/drivers/net/netfront.c
+++ b/src/drivers/net/netfront.c
@@ -511,15 +511,12 @@ static void netfront_refill_rx ( struct net_device *netdev ) {
struct xen_device *xendev = netfront->xendev;
struct io_buffer *iobuf;
struct netif_rx_request *request;
+ unsigned int refilled = 0;
int notify;
int rc;
- /* Do nothing if ring is already full */
- if ( netfront_ring_is_full ( &netfront->rx ) )
- return;
-
/* Refill ring */
- do {
+ while ( netfront_ring_fill ( &netfront->rx ) < NETFRONT_RX_FILL ) {
/* Allocate I/O buffer */
iobuf = alloc_iob ( PAGE_SIZE );
@@ -543,13 +540,17 @@ static void netfront_refill_rx ( struct net_device *netdev ) {
/* Move to next descriptor */
netfront->rx_fring.req_prod_pvt++;
+ refilled++;
- } while ( ! netfront_ring_is_full ( &netfront->rx ) );
+ }
/* Push new descriptors and notify backend if applicable */
- RING_PUSH_REQUESTS_AND_CHECK_NOTIFY ( &netfront->rx_fring, notify );
- if ( notify )
- netfront_send_event ( netfront );
+ if ( refilled ) {
+ RING_PUSH_REQUESTS_AND_CHECK_NOTIFY ( &netfront->rx_fring,
+ notify );
+ if ( notify )
+ netfront_send_event ( netfront );
+ }
}
/**
diff --git a/src/drivers/net/netfront.h b/src/drivers/net/netfront.h
index 38fd0a77..c95ed264 100644
--- a/src/drivers/net/netfront.h
+++ b/src/drivers/net/netfront.h
@@ -16,7 +16,20 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#define NETFRONT_NUM_TX_DESC 16
/** Number of receive ring entries */
-#define NETFRONT_NUM_RX_DESC 8
+#define NETFRONT_NUM_RX_DESC 32
+
+/** Receive ring fill level
+ *
+ * The xen-netback driver from kernels 3.18 to 4.2 inclusive have a
+ * bug (CA-163395) which prevents packet reception if fewer than 18
+ * receive descriptors are available. This was fixed in upstream
+ * kernel commit d5d4852 ("xen-netback: require fewer guest Rx slots
+ * when not using GSO").
+ *
+ * We provide 18 receive descriptors to avoid unpleasant silent
+ * failures on these kernel versions.
+ */
+#define NETFRONT_RX_FILL 18
/** Grant reference indices */
enum netfront_ref_index {
@@ -89,6 +102,21 @@ netfront_init_ring ( struct netfront_ring *ring, const char *ref_key,
}
/**
+ * Calculate descriptor ring fill level
+ *
+ * @v ring Descriptor ring
+ * @v fill Fill level
+ */
+static inline __attribute__ (( always_inline )) unsigned int
+netfront_ring_fill ( struct netfront_ring *ring ) {
+ unsigned int fill_level;
+
+ fill_level = ( ring->id_prod - ring->id_cons );
+ assert ( fill_level <= ring->count );
+ return fill_level;
+}
+
+/**
* Check whether or not descriptor ring is full
*
* @v ring Descriptor ring
@@ -96,11 +124,8 @@ netfront_init_ring ( struct netfront_ring *ring, const char *ref_key,
*/
static inline __attribute__ (( always_inline )) int
netfront_ring_is_full ( struct netfront_ring *ring ) {
- unsigned int fill_level;
- fill_level = ( ring->id_prod - ring->id_cons );
- assert ( fill_level <= ring->count );
- return ( fill_level >= ring->count );
+ return ( netfront_ring_fill ( ring ) >= ring->count );
}
/**
@@ -112,7 +137,7 @@ netfront_ring_is_full ( struct netfront_ring *ring ) {
static inline __attribute__ (( always_inline )) int
netfront_ring_is_empty ( struct netfront_ring *ring ) {
- return ( ring->id_prod == ring->id_cons );
+ return ( netfront_ring_fill ( ring ) == 0 );
}
/** A netfront NIC */