[PATCH net-next 1/5] gve: Add adminq mutex lock

Ziwei Xiao
2024-05-07T23:00:23Z

We were depending on the rtnl_lock to make sure there is only one adminq
command running at a time. But some commands may take too long to hold
the rtnl_lock, such as the upcoming flow steering operations. For such
situations, it can temporarily drop the rtnl_lock, and replace it for
these operations with a new adminq lock, which can ensure the adminq
command execution to be thread-safe.

Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
Reviewed-by: Praveen Kaligineedi <pkaligineedi@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
drivers/net/ethernet/google/gve/gve.h | 1 +
drivers/net/ethernet/google/gve/gve_adminq.c | 22 +++++++++++---------
2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h
index ae1e21c9b0a5..ca7fce17f2c0 100644
--- a/drivers/net/ethernet/google/gve/gve.h
+++ b/drivers/net/ethernet/google/gve/gve.h
@@ -724,6 +724,7 @@ struct gve_priv {
union gve_adminq_command *adminq;
dma_addr_t adminq_bus_addr;
struct dma_pool *adminq_pool;
+ struct mutex adminq_lock; /* Protects adminq command execution */
u32 adminq_mask; /* masks prod_cnt to adminq size */
u32 adminq_prod_cnt; /* free-running count of AQ cmds executed */
u32 adminq_cmd_fail; /* free-running count of AQ cmds failed */
diff --git a/drivers/net/ethernet/google/gve/gve_adminq.c b/drivers/net/ethernet/google/gve/gve_adminq.c
index 3df8243680d9..2c3ec5c3b114 100644
--- a/drivers/net/ethernet/google/gve/gve_adminq.c
+++ b/drivers/net/ethernet/google/gve/gve_adminq.c
@@ -284,6 +284,7 @@ int gve_adminq_alloc(struct device *dev, struct gve_priv *priv)
&priv->reg_bar0->adminq_base_address_lo);
iowrite32be(GVE_DRIVER_STATUS_RUN_MASK, &priv->reg_bar0->driver_status);
}
+ mutex_init(&priv->adminq_lock);
gve_set_admin_queue_ok(priv);
return 0;
}
@@ -511,28 +512,29 @@ static int gve_adminq_issue_cmd(struct gve_priv *priv,
return 0;
}

-/* This function is not threadsafe - the caller is responsible for any
- * necessary locks.
- * The caller is also responsible for making sure there are no commands
- * waiting to be executed.
- */
static int gve_adminq_execute_cmd(struct gve_priv *priv,
union gve_adminq_command *cmd_orig)
{
u32 tail, head;
int err;

+ mutex_lock(&priv->adminq_lock);
tail = ioread32be(&priv->reg_bar0->adminq_event_counter);
head = priv->adminq_prod_cnt;
- if (tail != head)
- // This is not a valid path
- return -EINVAL;
+ if (tail != head) {
+ err = -EINVAL;
+ goto out;
+ }

err = gve_adminq_issue_cmd(priv, cmd_orig);
if (err)
- return err;
+ goto out;

- return gve_adminq_kick_and_wait(priv);
+ err = gve_adminq_kick_and_wait(priv);
+
+out:
+ mutex_unlock(&priv->adminq_lock);
+ return err;
}

/* The device specifies that the management vector can either be the first irq
--
2.45.0.rc1.225.g2a3ae87e7f-goog