iflib: expose the Rx mbuf buffer size to drivers

From Jake:
iflib_fl_setup calculates a suitable buffer size for the Rx mbufs based
on the isc_max_frame_size value that drivers setup. This calculation is
repeated by drivers when programming their hardware with the size of
each Rx buffer.

This can lead to a mismatch where the iflib mbuf size is different from
the expected size of the buffer as programmed by the hardware. This can
lead to unexpected results.

If iflib ever wants to support mbuf sizes larger than one page, every
driver must be updated to account for the new possible buffer sizes.

Fix this by calculating the mbuf size prior to calling IFDI_INIT, and
adding the iflib_get_rx_mbuf_sz function which will expose this value to
drivers, so that they do not repeat the same calculation.

Submitted by:	Jacob Keller <jacob.e.keller@intel.com>
Reviewed by:	shurd@, erj@
MFC after:	1 week
Sponsored by:	Intel Corporation
Differential Revision:	https://reviews.freebsd.org/D19489

1 files changed, 31 insertions, 9 deletions

diff --git a/sys/net/iflib.c b/sys/net/iflib.c
index 694dd9b632fb..c1f1df1a3874 100644
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -171,6 +171,7 @@ struct iflib_ctx {
 	uint32_t ifc_if_flags;
 	uint32_t ifc_flags;
 	uint32_t ifc_max_fl_buf_size;
+	uint32_t ifc_rx_mbuf_sz;
 
 	int ifc_link_state;
 	int ifc_link_irq;
@@ -2172,7 +2173,6 @@ iflib_fl_setup(iflib_fl_t fl)
 {
 	iflib_rxq_t rxq = fl->ifl_rxq;
 	if_ctx_t ctx = rxq->ifr_ctx;
-	if_softc_ctx_t sctx = &ctx->ifc_softc_ctx;
 
 	bit_nclear(fl->ifl_rx_bitmap, 0, fl->ifl_size - 1);
 	/*
@@ -2181,14 +2181,7 @@ iflib_fl_setup(iflib_fl_t fl)
 	iflib_fl_bufs_free(fl);
 	/* Now replenish the mbufs */
 	MPASS(fl->ifl_credits == 0);
-	/*
-	 * XXX don't set the max_frame_size to larger
-	 * than the hardware can handle
-	 */
-	if (sctx->isc_max_frame_size <= 2048)
-		fl->ifl_buf_size = MCLBYTES;
-	else
-		fl->ifl_buf_size = MJUMPAGESIZE;
+	fl->ifl_buf_size = ctx->ifc_rx_mbuf_sz;
 	if (fl->ifl_buf_size > ctx->ifc_max_fl_buf_size)
 		ctx->ifc_max_fl_buf_size = fl->ifl_buf_size;
 	fl->ifl_cltype = m_gettype(fl->ifl_buf_size);
@@ -2314,6 +2307,27 @@ iflib_timer(void *arg)
 }
 
 static void
+iflib_calc_rx_mbuf_sz(if_ctx_t ctx)
+{
+	if_softc_ctx_t sctx = &ctx->ifc_softc_ctx;
+
+	/*
+	 * XXX don't set the max_frame_size to larger
+	 * than the hardware can handle
+	 */
+	if (sctx->isc_max_frame_size <= MCLBYTES)
+		ctx->ifc_rx_mbuf_sz = MCLBYTES;
+	else
+		ctx->ifc_rx_mbuf_sz = MJUMPAGESIZE;
+}
+
+uint32_t
+iflib_get_rx_mbuf_sz(if_ctx_t ctx)
+{
+	return (ctx->ifc_rx_mbuf_sz);
+}
+
+static void
 iflib_init_locked(if_ctx_t ctx)
 {
 	if_softc_ctx_t sctx = &ctx->ifc_softc_ctx;
@@ -2347,6 +2361,14 @@ iflib_init_locked(if_ctx_t ctx)
 		CALLOUT_UNLOCK(txq);
 		iflib_netmap_txq_init(ctx, txq);
 	}
+
+	/*
+	 * Calculate a suitable Rx mbuf size prior to calling IFDI_INIT, so
+	 * that drivers can use the value when setting up the hardware receive
+	 * buffers.
+	 */
+	iflib_calc_rx_mbuf_sz(ctx);
+
 #ifdef INVARIANTS
 	i = if_getdrvflags(ifp);
 #endif