Re: [PATCH] Revert "net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"

I would try something like :

Basically do not bother using CHECKSUM_COMPLETE for small frames that might have been padded.

Since we need to bring one cache line in eth_type_trans() and further header processing,
computing the checksum in software will be almost free anyway.

diff --git a/drivers/net/ethernet/sun/sungem.c b/drivers/net/ethernet/sun/sungem.c
index 7a16d40a72d13cf1d522e8a3a396c826fe76f9b9..071039f211a8a33153e888bd4014314ba5e686a4 100644
--- a/drivers/net/ethernet/sun/sungem.c
+++ b/drivers/net/ethernet/sun/sungem.c

@@ -855,9 +855,11 @@ static int gem_rx(struct gem *gp, int work_to_do)
                        skb = copy_skb;
                }
 
-               csum = (__force __sum16)htons((status & RXDCTRL_TCPCSUM) ^ 0xffff);
-               skb->csum = csum_unfold(csum);
-               skb->ip_summed = CHECKSUM_COMPLETE;
+               if (len > ETH_ZLEN) {
+                       csum = (__force __sum16)htons((status & RXDCTRL_TCPCSUM) ^ 0xffff);
+                       skb->csum = csum_unfold(csum);
+                       skb->ip_summed = CHECKSUM_COMPLETE;
+               }
                skb->protocol = eth_type_trans(skb, gp->dev);
 
                napi_gro_receive(&gp->napi, skb);