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gve: Upgrade memory barrier in poll routine

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[ Upstream commit f81781835f0adfae8d701545386030d223efcd6f ]

As currently written, if the driver checks for more work (via
gve_tx_poll or gve_rx_poll) before the device posts work and the
irq doorbell is not unmasked
(via iowrite32be(GVE_IRQ_ACK | GVE_IRQ_EVENT, ...)) before the device
attempts to raise an interrupt, an interrupt is lost and this could
potentially lead to the traffic being completely halted. For
example, if a tx queue has already been stopped, the driver won't get
the chance to complete work and egress will be halted.

We need a full memory barrier in the poll
routine to ensure that the irq doorbell is unmasked before the driver
checks for more work.

Fixes: f5cedc84a3 ("gve: Add transmit and receive support")
Signed-off-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David Awogbemila <awogbemila@google.com>
Acked-by: Willem de Brujin <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Catherine Sullivan 2021-05-17 14:08:14 -07:00 • committed by Greg Kroah-Hartman
commit 4f4752e4d8
1 changed files with 1 additions and 1 deletions
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2
drivers/net/ethernet/google/gve/gve_main.c
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@ -121,7 +121,7 @@ static int gve_napi_poll(struct napi_struct *napi, int budget)
/* Double check we have no extra work.
* Ensure unmask synchronizes with checking for work.
*/
dma_rmb();
mb();
if (block->tx)
reschedule |= gve_tx_poll(block, -1);
if (block->rx)