From 1c0e5701c5e792c090aef0e5b9b8923c334d9324 Mon Sep 17 00:00:00 2001

From: Liming Sun <limings@nvidia.com>

Date: Fri, 7 May 2021 20:30:12 -0400

Subject: [PATCH] platform/mellanox: mlxbf-tmfifo: Fix a memory barrier issue

Git-commit: 1c0e5701c5e792c090aef0e5b9b8923c334d9324

Patch-mainline: v5.13-rc3

References: git-fixes

The virtio framework uses wmb() when updating avail->idx. It

guarantees the write order, but not necessarily loading order

for the code accessing the memory. This commit adds a load barrier

after reading the avail->idx to make sure all the data in the

descriptor is visible. It also adds a barrier when returning the

packet to virtio framework to make sure read/writes are visible to

the virtio code.

Fixes: 1357dfd7261f ("platform/mellanox: Add TmFifo driver for Mellanox BlueField Soc")

Signed-off-by: Liming Sun <limings@nvidia.com>

Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>

Link: https://lore.kernel.org/r/1620433812-17911-1-git-send-email-limings@nvidia.com

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/platform/mellanox/mlxbf-tmfifo.c | 11 ++++++++++-

 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c

index bbc4e71a16ff..38800e86ed8a 100644

--- a/drivers/platform/mellanox/mlxbf-tmfifo.c

+++ b/drivers/platform/mellanox/mlxbf-tmfifo.c

@@ -294,6 +294,9 @@ mlxbf_tmfifo_get_next_desc(struct mlxbf_tmfifo_vring *vring)

 	if (vring->next_avail == virtio16_to_cpu(vdev, vr->avail->idx))

 		return NULL;

+	/* Make sure 'avail->idx' is visible already. */

+	virtio_rmb(false);

+

 	idx = vring->next_avail % vr->num;

 	head = virtio16_to_cpu(vdev, vr->avail->ring[idx]);

 	if (WARN_ON(head >= vr->num))

@@ -322,7 +325,7 @@ static void mlxbf_tmfifo_release_desc(struct mlxbf_tmfifo_vring *vring,

 	 * done or not. Add a memory barrier here to make sure the update above

 	 * completes before updating the idx.

 	 */

-	mb();

+	virtio_mb(false);

 	vr->used->idx = cpu_to_virtio16(vdev, vr_idx + 1);

 }

@@ -733,6 +736,12 @@ static bool mlxbf_tmfifo_rxtx_one_desc(struct mlxbf_tmfifo_vring *vring,

 		desc = NULL;

 		fifo->vring[is_rx] = NULL;

+		/*

+		 * Make sure the load/store are in order before

+		 * returning back to virtio.

+		 */

+		virtio_mb(false);

+

 		/* Notify upper layer that packet is done. */

 		spin_lock_irqsave(&fifo->spin_lock[is_rx], flags);

 		vring_interrupt(0, vring->vq);

-- 

2.26.2