[openib-general] [PATCH 5 of 5] IB/mthca: give reserved MTTs a separate cache line

[Michael S. Tsirkin]

MTTs are allocated in non-cache-coherent memory, so we must give
reserved MTTs their own cache line, to prevent both device and
CPU from writing into the same cache line at the same time.

Signed-off-by: Michael S. Tsirkin <mst at mellanox.co.il>

---

Index: linux-2.6/drivers/infiniband/hw/mthca/mthca_main.c
===================================================================
--- linux-2.6.orig/drivers/infiniband/hw/mthca/mthca_main.c
+++ linux-2.6/drivers/infiniband/hw/mthca/mthca_main.c
@@ -464,6 +464,10 @@ static int mthca_init_icm(struct mthca_d
 		goto err_unmap_aux;
 	}
 
+	/* CPU writes to non-reserved MTTs, while HCA might DMA to reserved mtts */
+	mdev->limits.reserved_mtts = max(dma_get_cache_alignment() / (int)sizeof(u64),
+					 mdev->limits.reserved_mtts);
+
 	mdev->mr_table.mtt_table = mthca_alloc_icm_table(mdev, init_hca->mtt_base,
 							 MTHCA_MTT_SEG_SIZE,
 							 mdev->limits.num_mtt_segs,

-- 
MST