From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 451576FA0 for ; Mon, 16 Jan 2023 16:46:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2446C433D2; Mon, 16 Jan 2023 16:46:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673887574; bh=fmTl9L0LGI6dAV1eOH+ukGGUNMBs1nt2hfg/7FjgvhY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q7DeSzTuUOIF5mlMxItmul3cdC7Ex/tct5QXeiMWA0v9m2EcxcxGhbuh6Od4IeQ26 ooS4IyBeoGCR89dtrDgYvyhTFc41RrEy6oFLG5Vgj/YDfgNLzcpzNrxfPGVfRQQScp 2F7s9Nu4uza1YjMuo40MLs8uXXQv19VMJCZQUCYc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Pilmore , Dave Jiang , Jakub Kicinski , Sasha Levin Subject: [PATCH 4.19 172/521] ntb_netdev: Use dev_kfree_skb_any() in interrupt context Date: Mon, 16 Jan 2023 16:47:14 +0100 Message-Id: <20230116154854.799487767@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154847.246743274@linuxfoundation.org> References: <20230116154847.246743274@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eric Pilmore [ Upstream commit 5f7d78b2b12a9d561f48fa00bab29b40f4616dad ] TX/RX callback handlers (ntb_netdev_tx_handler(), ntb_netdev_rx_handler()) can be called in interrupt context via the DMA framework when the respective DMA operations have completed. As such, any calls by these routines to free skb's, should use the interrupt context safe dev_kfree_skb_any() function. Previously, these callback handlers would call the interrupt unsafe version of dev_kfree_skb(). This has not presented an issue on Intel IOAT DMA engines as that driver utilizes tasklets rather than a hard interrupt handler, like the AMD PTDMA DMA driver. On AMD systems, a kernel WARNING message is encountered, which is being issued from skb_release_head_state() due to in_hardirq() being true. Besides the user visible WARNING from the kernel, the other symptom of this bug was that TCP/IP performance across the ntb_netdev interface was very poor, i.e. approximately an order of magnitude below what was expected. With the repair to use dev_kfree_skb_any(), kernel WARNINGs from skb_release_head_state() ceased and TCP/IP performance, as measured by iperf, was on par with expected results, approximately 20 Gb/s on AMD Milan based server. Note that this performance is comparable with Intel based servers. Fixes: 765ccc7bc3d91 ("ntb_netdev: correct skb leak") Fixes: 548c237c0a997 ("net: Add support for NTB virtual ethernet device") Signed-off-by: Eric Pilmore Reviewed-by: Dave Jiang Link: https://lore.kernel.org/r/20221209000659.8318-1-epilmore@gigaio.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/ntb_netdev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ntb_netdev.c b/drivers/net/ntb_netdev.c index 33974e7519ce..ca0053775d3f 100644 --- a/drivers/net/ntb_netdev.c +++ b/drivers/net/ntb_netdev.c @@ -140,7 +140,7 @@ static void ntb_netdev_rx_handler(struct ntb_transport_qp *qp, void *qp_data, enqueue_again: rc = ntb_transport_rx_enqueue(qp, skb, skb->data, ndev->mtu + ETH_HLEN); if (rc) { - dev_kfree_skb(skb); + dev_kfree_skb_any(skb); ndev->stats.rx_errors++; ndev->stats.rx_fifo_errors++; } @@ -195,7 +195,7 @@ static void ntb_netdev_tx_handler(struct ntb_transport_qp *qp, void *qp_data, ndev->stats.tx_aborted_errors++; } - dev_kfree_skb(skb); + dev_kfree_skb_any(skb); if (ntb_transport_tx_free_entry(dev->qp) >= tx_start) { /* Make sure anybody stopping the queue after this sees the new -- 2.35.1