From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.tipi-net.de (mail.tipi-net.de [194.13.80.246]) (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 E470E3C5DBE; Thu, 2 Apr 2026 11:29:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.13.80.246 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775129362; cv=none; b=o1bjoooaoC/aBcDinmrp5wLaj6gJESMeOBcBrDJhvtTPEAct1B4tHzy0pyTm2j5shZix6xfuEYuiT0I4wUWriAqlHgmQZPauFfG6S77V1lPSM157qsWLfeDGq6faUmJNwdwVxXojUKy8anDYURvi6/hST4wZxdgNWcF2L1MsOgM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775129362; c=relaxed/simple; bh=UFM3F4KxTa/Q/A6kQ2KBWsGLMi8ygz/21/zclF/AMew=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=FK4qRdkj1Nxqq0BPObdwA8My/MyJcGvnxK9xEmuA/aeGnTvcrOuy7DkAE9BtCej669NlWsI4OPgKFZf8vfBLprztnSPda4/ApnmiGOPedEcSLDiyTZqjZMr8GcFbjBnTcRoKuRGv0YVxURmL+c0AwIiSqM6VjVERrDOhhem4jGQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de; spf=pass smtp.mailfrom=tipi-net.de; dkim=pass (2048-bit key) header.d=tipi-net.de header.i=@tipi-net.de header.b=IcmjhvQf; arc=none smtp.client-ip=194.13.80.246 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=tipi-net.de header.i=@tipi-net.de header.b="IcmjhvQf" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 51FB6A5888; Thu, 2 Apr 2026 13:29:08 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tipi-net.de; s=dkim; t=1775129350; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=S6Fc+VQFNJS59febgRn5r7bQIXRkfyasJ4vaWi2ydds=; b=IcmjhvQfDyvEvVVKXQmqSORotoC1OhiBAhN2nE4jTRwaow33IY8SGWASuzdmP/gQPm6tBY 5uRT3ZQHHeY1hwa4GRNzyYMpsWbWilxqR2WSHkVqZr5CULNgMRlk9JFBzuJ5ArSZGnJ4NJ QCJTasyNQcqIgZv8yrdPzEOB+Eh2e1AK2xC9uuKFDDsPRNrzQZeix6jT8TB4qhfOlurlN+ Oilg85Po74PQwvE3fEU5FuDTcNL7Jwbph4wIu0W22T3qsd51eeChPyY7vtPBQ8OET4XU9P 6pt/krU45O7hS+Jr3J7qo2pZRegZsNS4g/SwK4kZEEAY9Gubq+t3CYIgqv+KDQ== Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Thu, 02 Apr 2026 13:29:08 +0200 From: Nicolai Buchwitz To: =?UTF-8?Q?Th=C3=A9o_Lebrun?= Cc: Nicolas Ferre , Claudiu Beznea , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Richard Cochran , Russell King , Paolo Valerio , Conor Dooley , Vladimir Kondratiev , Gregory CLEMENT , =?UTF-8?Q?Beno=C3=AEt_Monin?= , Tawfik Bayouk , Thomas Petazzoni , Maxime Chevallier , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 10/11] net: macb: use context swapping in .set_ringparam() In-Reply-To: <20260401-macb-context-v1-10-9590c5ab7272@bootlin.com> References: <20260401-macb-context-v1-0-9590c5ab7272@bootlin.com> <20260401-macb-context-v1-10-9590c5ab7272@bootlin.com> Message-ID: <90f843aa3940bdbabadddce27314c1f1@tipi-net.de> X-Sender: nb@tipi-net.de Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 On 1.4.2026 18:39, Théo Lebrun wrote: > ethtool_ops.set_ringparam() is implemented using the primitive close / > update ring size / reopen sequence. Under memory pressure this does not > fly: we free our buffers at close and cannot reallocate new ones at > open. Also, it triggers a slow PHY reinit. > > Instead, exploit the new context mechanism and improve our sequence to: > - allocate a new context (including buffers) first > - if it fails, early return without any impact to the interface > - stop interface > - update global state (bp, netdev, etc) > - pass buffer pointers to the hardware > - start interface > - free old context. > > The HW disable sequence is inspired by macb_reset_hw() but avoids > (1) setting NCR bit CLRSTAT and (2) clearing register PBUFRXCUT. > > The HW re-enable sequence is inspired by macb_mac_link_up(), skipping > over register writes which would be redundant (because values have not > changed). > > The generic context swapping parts are isolated into helper functions > macb_context_swap_start|end(), reusable by other operations > (change_mtu, > set_channels, etc). > > Signed-off-by: Théo Lebrun > --- > drivers/net/ethernet/cadence/macb_main.c | 89 > +++++++++++++++++++++++++++++--- > 1 file changed, 82 insertions(+), 7 deletions(-) > > diff --git a/drivers/net/ethernet/cadence/macb_main.c > b/drivers/net/ethernet/cadence/macb_main.c > index 42b19b969f3e..543356554c11 100644 > --- a/drivers/net/ethernet/cadence/macb_main.c > +++ b/drivers/net/ethernet/cadence/macb_main.c > @@ -2905,6 +2905,76 @@ static struct macb_context > *macb_context_alloc(struct macb *bp, > return ctx; > } > > +static void macb_context_swap_start(struct macb *bp) > +{ > + struct macb_queue *queue; > + unsigned int q; > + u32 ctrl; > + > + /* Disable software Tx, disable HW Tx/Rx and disable NAPI. */ > + > + netif_tx_disable(bp->netdev); > + > + ctrl = macb_readl(bp, NCR); > + macb_writel(bp, NCR, ctrl & ~(MACB_BIT(RE) | MACB_BIT(TE))); > + > + macb_writel(bp, TSR, -1); > + macb_writel(bp, RSR, -1); > + > + for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { > + queue_writel(queue, IDR, -1); > + queue_readl(queue, ISR); > + if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE) > + queue_writel(queue, ISR, -1); > + } > + > + for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { > + napi_disable(&queue->napi_rx); > + napi_disable(&queue->napi_tx); > + } tx_error_task, hresp_err_bh_work, and tx_lpi_work all dereference bp->ctx and could race with the pointer swap in swap_end. macb_close() cancels at least tx_lpi_work here. Should these be flushed too? > +} > + > +static void macb_context_swap_end(struct macb *bp, > + struct macb_context *new_ctx) > +{ > + struct macb_context *old_ctx; > + struct macb_queue *queue; > + unsigned int q; > + u32 ctrl; > + > + /* Swap contexts & give buffer pointers to HW. */ > + > + old_ctx = bp->ctx; > + bp->ctx = new_ctx; > + macb_init_buffers(bp); > + > + /* Start NAPI, HW Tx/Rx and software Tx. */ > + > + for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { > + napi_enable(&queue->napi_rx); > + napi_enable(&queue->napi_tx); > + } > + > + if (!(bp->caps & MACB_CAPS_MACB_IS_EMAC)) { > + for (q = 0, queue = bp->queues; q < bp->num_queues; > + ++q, ++queue) { > + queue_writel(queue, IER, > + bp->rx_intr_mask | > + MACB_TX_INT_FLAGS | > + MACB_BIT(HRESP)); > + } > + } > + > + ctrl = macb_readl(bp, NCR); > + macb_writel(bp, NCR, ctrl | MACB_BIT(RE) | MACB_BIT(TE)); > + > + netif_tx_start_all_queues(bp->netdev); > + > + /* Free old context. */ > + > + macb_free_consistent(old_ctx); 1. kfree(old_ctx) is missing. The context struct itself leaks on every swap. 2. macb_close() calls netdev_tx_reset_queue() for each queue. Shouldn't the swap do the same? BQL accounting will be stale after switching to a fresh context. 3. macb_configure_dma() is not called after the swap. For set_ringparam this is probably fine since rx_buffer_size does not change, but this becomes a problem in patch 11. > [...]