Messages in this thread | | | Subject | Re: Kernel Panic in skb_release_data using genet | From | Florian Fainelli <> | Date | Fri, 2 Jul 2021 09:49:31 -0700 |
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Hey Maxime,
On 6/25/2021 5:59 AM, Maxime Ripard wrote: > Hi Florian, > > Sorry for the late reply > > On Thu, Jun 10, 2021 at 02:33:17PM -0700, Florian Fainelli wrote: >> On 6/2/2021 6:28 AM, Maxime Ripard wrote: >>> On Tue, Jun 01, 2021 at 11:33:18AM +0200, nicolas saenz julienne wrote: >>>> On Mon, 2021-05-31 at 19:36 -0700, Florian Fainelli wrote: >>>>>> That is also how I boot my Pi4 at home, and I suspect you are right, if >>>>>> the VPU does not shut down GENET's DMA, and leaves buffer addresses in >>>>>> the on-chip descriptors that point to an address space that is managed >>>>>> totally differently by Linux, then we can have a serious problem and >>>>>> create some memory corruption when the ring is being reclaimed. I will >>>>>> run a few experiments to test that theory and there may be a solution >>>>>> using the SW_INIT reset controller to have a big reset of the controller >>>>>> before handing it over to the Linux driver. >>>>> >>>>> Adding a WARN_ON(reg & DMA_EN) in bcmgenet_dma_disable() has not shown >>>>> that the TX or RX DMA have been left running during the hand over from >>>>> the VPU to the kernel. I checked out drm-misc-next-2021-05-17 to reduce >>>>> as much as possible the differences between your set-up and my set-up >>>>> but so far have not been able to reproduce the crash in booting from NFS >>>>> repeatedly, I will try again. >>>> >>>> FWIW I can reproduce the error too. That said it's rather hard to reproduce, >>>> something in the order of 1 failure every 20 tries. >>> >>> Yeah, it looks like it's only from a cold boot and comes in "bursts", >>> where you would get like 5 in a row and be done with it for a while. >> >> Here are two patches that you could try exclusive from one another >> >> 1) Limit GENET to a single queue >> >> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> index fcca023f22e5..e400c12e6868 100644 >> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> @@ -3652,6 +3652,12 @@ static int bcmgenet_change_carrier(struct >> net_device *dev, bool new_carrier) >> return 0; >> } >> >> +static u16 bcmgenet_select_queue(struct net_device *dev, struct sk_buff >> *skb, >> + struct net_device *sb_dev) >> +{ >> + return 0; >> +} >> + >> static const struct net_device_ops bcmgenet_netdev_ops = { >> .ndo_open = bcmgenet_open, >> .ndo_stop = bcmgenet_close, >> @@ -3666,6 +3672,7 @@ static const struct net_device_ops >> bcmgenet_netdev_ops = { >> #endif >> .ndo_get_stats = bcmgenet_get_stats, >> .ndo_change_carrier = bcmgenet_change_carrier, >> + .ndo_select_queue = bcmgenet_select_queue, >> }; >> >> /* Array of GENET hardware parameters/characteristics */ >> >> 2) Ensure that all TX/RX queues are disabled upon DMA initialization >> >> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> index fcca023f22e5..7f8a5996fbbb 100644 >> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c >> @@ -3237,15 +3237,21 @@ static void bcmgenet_get_hw_addr(struct >> bcmgenet_priv *priv, >> /* Returns a reusable dma control register value */ >> static u32 bcmgenet_dma_disable(struct bcmgenet_priv *priv) >> { >> + unsigned int i; >> u32 reg; >> u32 dma_ctrl; >> >> /* disable DMA */ >> dma_ctrl = 1 << (DESC_INDEX + DMA_RING_BUF_EN_SHIFT) | DMA_EN; >> + for (i = 0; i < priv->hw_params->tx_queues; i++) >> + dma_ctrl |= (1 << (i + DMA_RING_BUF_EN_SHIFT)); >> reg = bcmgenet_tdma_readl(priv, DMA_CTRL); >> reg &= ~dma_ctrl; >> bcmgenet_tdma_writel(priv, reg, DMA_CTRL); >> >> + dma_ctrl = 1 << (DESC_INDEX + DMA_RING_BUF_EN_SHIFT) | DMA_EN; >> + for (i = 0; i < priv->hw_params->rx_queues; i++) >> + dma_ctrl |= (1 << (i + DMA_RING_BUF_EN_SHIFT)); >> reg = bcmgenet_rdma_readl(priv, DMA_CTRL); >> reg &= ~dma_ctrl; >> bcmgenet_rdma_writel(priv, reg, DMA_CTRL); > > I had a bunch of issues popping up today so I took the occasion to test > those patches. The first one doesn't change anything, I still had the > crash occurring with it. With the second applied (in addition), it seems > like it's fixed. I'll keep testing and will let you know.
Did this patch survive more days of testing? I am tempted to send it regardless of your testing because it is a correctness issue that is being fixed. There is a global DMA enable bit which should "cut" any TX/RX queues, but still, for symmetry with other code paths all queues should be disabled.
Thanks! -- Florian
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