[PATCH] vdpa/mlx5: workaround var offset within page

[Yajun Wu <yajunw@nvidia.com>]

vDPA driver first uses kernel driver to allocate doorbell(VAR) area for
each device. Then uses var->mmap_off and var->length to mmap uverbs device
file as doorbell userspace virtual address.

Current kernel driver provides var->mmap_off equal to page start of VAR.
It's fine with x86 4K page server, because VAR physical address is only 4K
aligned thus locate in 4K page start.

But with aarch64 64K page server, the actual VAR physical address has
offset within page(not locate in 64K page start). So vDPA driver need add
this within page offset(caps.doorbell_bar_offset) to get right VAR virtual
address.

Fixes: 62c813706e4 ("vdpa/mlx5: map doorbell")
Cc: stable@dpdk.org

Signed-off-by: Yajun Wu <yajunw@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>
---
 drivers/vdpa/mlx5/mlx5_vdpa_virtq.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c b/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c
index 3416797d28..0748710a76 100644
--- a/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c
+++ b/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c
@@ -9,6 +9,7 @@
 #include <rte_malloc.h>
 #include <rte_errno.h>
 #include <rte_io.h>
+#include <rte_eal_paging.h>
 
 #include <mlx5_common.h>
 
@@ -123,7 +124,10 @@ mlx5_vdpa_virtqs_release(struct mlx5_vdpa_priv *priv)
 		priv->td = NULL;
 	}
 	if (priv->virtq_db_addr) {
-		claim_zero(munmap(priv->virtq_db_addr, priv->var->length));
+		/* Mask out the within page offset for ummap. */
+		claim_zero(munmap((void *)((uint64_t)priv->virtq_db_addr &
+			~(rte_mem_page_size() - 1ULL)),
+			priv->var->length));
 		priv->virtq_db_addr = NULL;
 	}
 	priv->features = 0;
@@ -486,6 +490,10 @@ mlx5_vdpa_virtqs_prepare(struct mlx5_vdpa_priv *priv)
 		priv->virtq_db_addr = NULL;
 		goto error;
 	} else {
+		/* Add within page offset for 64K page system. */
+		priv->virtq_db_addr = (char *)priv->virtq_db_addr +
+			((rte_mem_page_size() - 1) &
+			priv->caps.doorbell_bar_offset);
 		DRV_LOG(DEBUG, "VAR address of doorbell mapping is %p.",
 			priv->virtq_db_addr);
 	}
-- 
2.27.0