RDMA/cxgb4: Limit MRs to < 8GB for T4/T5 devices

T4/T5 hardware can't handle MRs >= 8GB due to a hardware bug.  So limit
registrations to < 8GB for thse devices.

Based on original work by Steve Wise <swise@opengridcomputing.com>.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/cxgb4/mem.c

@@ -50,6 +50,13 @@ static int inline_threshold = C4IW_INLINE_THRESHOLD;
 module_param(inline_threshold, int, 0644);
 MODULE_PARM_DESC(inline_threshold, "inline vs dsgl threshold (default=128)");
 
+static int mr_exceeds_hw_limits(struct c4iw_dev *dev, u64 length)
+{
+	return (is_t4(dev->rdev.lldi.adapter_type) ||
+		is_t5(dev->rdev.lldi.adapter_type)) &&
+		length >= 8*1024*1024*1024ULL;
+}
+
 static int _c4iw_write_mem_dma_aligned(struct c4iw_rdev *rdev, u32 addr,
 				       u32 len, dma_addr_t data, int wait)
 {
@@ -538,6 +545,11 @@ int c4iw_reregister_phys_mem(struct ib_mr *mr, int mr_rereg_mask,
 			return ret;
 	}
 
+	if (mr_exceeds_hw_limits(rhp, total_size)) {
+		kfree(page_list);
+		return -EINVAL;
+	}
+
 	ret = reregister_mem(rhp, php, &mh, shift, npages);
 	kfree(page_list);
 	if (ret)
@@ -598,6 +610,12 @@ struct ib_mr *c4iw_register_phys_mem(struct ib_pd *pd,
 	if (ret)
 		goto err;
 
+	if (mr_exceeds_hw_limits(rhp, total_size)) {
+		kfree(page_list);
+		ret = -EINVAL;
+		goto err;
+	}
+
 	ret = alloc_pbl(mhp, npages);
 	if (ret) {
 		kfree(page_list);
@@ -701,6 +719,10 @@ struct ib_mr *c4iw_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 
 	php = to_c4iw_pd(pd);
 	rhp = php->rhp;
+
+	if (mr_exceeds_hw_limits(rhp, length))
+		return ERR_PTR(-EINVAL);
+
 	mhp = kzalloc(sizeof(*mhp), GFP_KERNEL);
 	if (!mhp)
 		return ERR_PTR(-ENOMEM);