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Miller" , Eric Dumazet , Paolo Abeni , Maxime Coquelin , xfr@outlook.com, Suraj Jaiswal , Thierry Reding , "linux-tegra@vger.kernel.org" , Will Deacon References: <20241202163309.05603e96@kernel.org> <20241203100331.00007580@gmail.com> <20241202183425.4021d14c@kernel.org> <20241203111637.000023fe@gmail.com> <2g2lp3bkadc4wpeslmdoexpidoiqzt7vejar5xhjx5ayt3uox3@dqdyfzn6khn6> <9719982a-d40c-4110-9233-def2e6cb4d74@nvidia.com> From: Jon Hunter Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: LNXP265CA0055.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:5d::19) To SJ2PR12MB8784.namprd12.prod.outlook.com (2603:10b6:a03:4d0::11) Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR12MB8784:EE_|IA0PR12MB8893:EE_ X-MS-Office365-Filtering-Correlation-Id: 06035efe-4166-4b11-18b9-08dd151bb28b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016; 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I suppose this could simply be >>>>> hiding any subsequent errors, so once this is fixed we might see other >>>>> similar issues. >>>> >>>> Well, having a quick look at this, the first thing which stands out is: >>>> >>>> In stmmac_tx_clean(), we have: >>>> >>>> if (likely(tx_q->tx_skbuff_dma[entry].buf && >>>> tx_q->tx_skbuff_dma[entry].buf_type != STMMAC_TXBUF_T >>>> _XDP_TX)) { >>>> if (tx_q->tx_skbuff_dma[entry].map_as_page) >>>> dma_unmap_page(priv->device, >>>> tx_q->tx_skbuff_dma[entry].buf, >>>> tx_q->tx_skbuff_dma[entry].len, >>>> DMA_TO_DEVICE); >>>> else >>>> dma_unmap_single(priv->device, >>>> tx_q->tx_skbuff_dma[entry].buf, >>>> tx_q->tx_skbuff_dma[entry].len, >>>> DMA_TO_DEVICE); >>>> tx_q->tx_skbuff_dma[entry].buf = 0; >>>> tx_q->tx_skbuff_dma[entry].len = 0; >>>> tx_q->tx_skbuff_dma[entry].map_as_page = false; >>>> } >>>> >>>> So, tx_skbuff_dma[entry].buf is expected to point appropriately to the >>>> DMA region. >>>> >>>> Now if we look at stmmac_tso_xmit(): >>>> >>>> des = dma_map_single(priv->device, skb->data, skb_headlen(skb), >>>> DMA_TO_DEVICE); >>>> if (dma_mapping_error(priv->device, des)) >>>> goto dma_map_err; >>>> >>>> if (priv->dma_cap.addr64 <= 32) { >>>> ... >>>> } else { >>>> ... >>>> des += proto_hdr_len; >>>> ... >>>> } >>>> >>>> tx_q->tx_skbuff_dma[tx_q->cur_tx].buf = des; >>>> tx_q->tx_skbuff_dma[tx_q->cur_tx].len = skb_headlen(skb); >>>> tx_q->tx_skbuff_dma[tx_q->cur_tx].map_as_page = false; >>>> tx_q->tx_skbuff_dma[tx_q->cur_tx].buf_type = STMMAC_TXBUF_T_SKB; >>>> >>>> This will result in stmmac_tx_clean() calling dma_unmap_single() using >>>> "des" and "skb_headlen(skb)" as the buffer start and length. >>>> >>>> One of the requirements of the DMA mapping API is that the DMA handle >>>> returned by the map operation will be passed into the unmap function. >>>> Not something that was offset. The length will also be the same. >>>> >>>> We can clearly see above that there is a case where the DMA handle has >>>> been offset by proto_hdr_len, and when this is so, the value that is >>>> passed into the unmap operation no longer matches this requirement. >>>> >>>> So, a question to the reporter - what is the value of >>>> priv->dma_cap.addr64 in your failing case? You should see the value >>>> in the "Using %d/%d bits DMA host/device width" kernel message. >>> >>> It is ... >>> >>> dwc-eth-dwmac 2490000.ethernet: Using 40/40 bits DMA host/device width >> >> So yes, "des" is being offset, which will upset the unmap operation. >> Please try the following patch, thanks: >> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c >> index 9b262cdad60b..c81ea8cdfe6e 100644 >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c >> @@ -4192,8 +4192,8 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev) >> struct stmmac_txq_stats *txq_stats; >> struct stmmac_tx_queue *tx_q; >> u32 pay_len, mss, queue; >> + dma_addr_t tso_des, des; >> u8 proto_hdr_len, hdr; >> - dma_addr_t des; >> bool set_ic; >> int i; >> >> @@ -4289,14 +4289,15 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev) >> >> /* If needed take extra descriptors to fill the remaining payload */ >> tmp_pay_len = pay_len - TSO_MAX_BUFF_SIZE; >> + tso_des = des; >> } else { >> stmmac_set_desc_addr(priv, first, des); >> tmp_pay_len = pay_len; >> - des += proto_hdr_len; >> + tso_des = des + proto_hdr_len; >> pay_len = 0; >> } >> >> - stmmac_tso_allocator(priv, des, tmp_pay_len, (nfrags == 0), queue); >> + stmmac_tso_allocator(priv, tso_des, tmp_pay_len, (nfrags == 0), queue); >> >> /* In case two or more DMA transmit descriptors are allocated for this >> * non-paged SKB data, the DMA buffer address should be saved to > > I see, that makes sense. Looks like this has been broken for a few years > (since commit 34c15202896d ("net: stmmac: Fix the problem of tso_xmit")) > and Furong's patch ended up exposing it. > > Anyway, this seems to fix it for me. I can usually trigger the issue > within one or two iperf runs, with your patch I haven't seen it break > after a dozen or so runs. > > It may be good to have Jon's test results as well, but looks good so > far. I have been running tests on my side and so far so good too. I have not seen any more mapping failure cases. Russell, if you are planning to send a fix for this, please add my ... Tested-by: Jon Hunter Thanks! Jon -- nvpublic