From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f44.google.com (mail-wm1-f44.google.com [209.85.128.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B8F92E11B5; Tue, 8 Jul 2025 15:23:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751988232; cv=none; b=JbgG2rqrVyNxU2KG7Zw/yM80v/axu7VeIiz9iKgvAC8oOB9ONSmhxuXa1V63U/MU+N9FIuJLBpYiosfQ4SZoPwgG5FeF7rlCBgwSz+LHfgx/S4qcvNtLCVHdXJz2zeTG5xIk3fTxAdrkmbjyfFr7PGNxRITuUQQnOJxRvEV0qpQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751988232; c=relaxed/simple; bh=t0zhsMdWcVtROYyTguyTKLpSA22YsdUrHGfVAEnY4hg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ROEgx3QV4G4V3cTaRybsD42AzNAfGke4J8DxkPRM+gdnO9OtdJooqc+YFsd5ZkS+c5qBqjwtg7ml55cdG5mVv4LmkoBn/6RxEDEOTSEY96JVCGulDec8ENl9+6Ns3MjMYrpwliayoHhjQjCMlFNa1NDHx2niDK49O1wozw+by2Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=PuvyT2zn; arc=none smtp.client-ip=209.85.128.44 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PuvyT2zn" Received: by mail-wm1-f44.google.com with SMTP id 5b1f17b1804b1-450cf0120cdso38982525e9.2; Tue, 08 Jul 2025 08:23:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1751988228; x=1752593028; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=kcMUZCgeyReQcwT7hAu7bby9I4CBSBEcQAsKrmRUZHU=; b=PuvyT2zn1yIrIZFJUdRZ8levt3/HmGfLYqqwjNkk4lucAEHpoDJGCXDN2LD4up2FgR Fr8cnUtqnrBP722pc+dhjWqQumSW6wX3iP7SFAwpFIsh276GUOuzD/IFouqFqyD1Vagu qDCb+wPqQjYU6XT/c9Zx6D7afzZDH6s3MJYDfAD7tpYcUSuTFToTvqu54lKHBKfKsy7t 0LZ6nMNMfZ3cshTPGoQPEEBLUrfRBVPJ9tVTJOl+0O95cl98duDq1Fjwd6Y6CkDWcMD5 /lLbmW7QpPdr9RMo9hzOVgN9c/OD4bZZ4vUkbLtyosWxFVXYmne3f/Q7NmO35HigWlQv zWWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751988228; x=1752593028; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=kcMUZCgeyReQcwT7hAu7bby9I4CBSBEcQAsKrmRUZHU=; b=q3LZ+h2oSumlmVYBwzIMZUa9yM3pzStmwR1nQugIDvwCGxUQ8KcltRfm1hdRQU2rrO SV1lGXj/L4qEAorRr3ksEQbGPx/qnsnxp7xgw4jV1sP0EfFv9hFuFMSt5IJythhzij8Z gICt28OWjOL1FfWNIExuw2/COGDG9h/7CKF3QXOJvoGSBzUUt2ubUqCxR1YPMfwP2Wx5 soai6zI+ZX5uNT3lG6mFitQh2e/bpunMsSwsIHwolV1kxVA1gaDDH93GLmTbAVNT88YE pCv5Pt29vcwOJm2BHZ5auQltauhupkxg3JhV3eMets4RtB9qdp/ZaVh2Wf8c28sFMPGM 9Gbw== X-Forwarded-Encrypted: i=1; AJvYcCV5EK1rcMGNOoKnssNlpiK9+I+iBG2G28h50ipiMv2WZx3xOOtFWjuGn3DMwVL4mY5Vehha37++iVJ6KB8=@vger.kernel.org, AJvYcCW6lOAeZp3+OswamrP3X8ZjwVG7buoxgj5uBKJll71Pev2G2/54VXTVb97LQRSbjXSRya89XIOK@vger.kernel.org X-Gm-Message-State: AOJu0Yx+TQgP9LfadVnqLSnfodfoxHb3Ii+Q2cPogvjSB0GF38FoYj9D M5GV0p9Q3yVg/LVwY4uMxNr374LfS7NvIV6S+JTarnsTdszYTQOwpOHe X-Gm-Gg: ASbGnctfFPG11BsNOlON5oOyrwXfTLvYEnfGA1DCYqIgfww1l9l1XpwiH85gtChGWTk kAEAHs+NwaviXszRGfl7cxDupP0LAX7XRWu4JcxS/xG/v00IHcZiOIrwXRoVEdkChkOHHblvrMS WzzCvRUs3ON8FT11h8kdLmEvVA/AYCHMJctSrk5qqMIQF4a9TTHw5q8E2L9la30aLPiBompZFYQ 5NoFjOwRXgHehDOr7W6HdEErmXyJq4pJt2e7mCGcDLAQc9mwN8vZLoxjPKiBi8z9ukyhVphL9gL RByscI/R1a8oKtQbzblMt887eIEbmyWd+RzttFaeXvjOPdkbyUNa8BbbwtTj8i6tPZqtXsc= X-Google-Smtp-Source: AGHT+IFFRv7FyHwKi0RG8N4S4cEq/NWk0eTLY0KyjYMqoY8o5cwORJ/c7bHpDiinkUqtv3tNuYGFpw== X-Received: by 2002:a05:600c:4706:b0:454:a37a:db67 with SMTP id 5b1f17b1804b1-454b4ead1c5mr181254015e9.17.1751988228002; Tue, 08 Jul 2025 08:23:48 -0700 (PDT) Received: from [192.168.8.100] ([185.69.144.115]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b47030bc79sm13226959f8f.9.2025.07.08.08.23.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Jul 2025 08:23:47 -0700 (PDT) Message-ID: Date: Tue, 8 Jul 2025 16:25:13 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC net-next 1/4] net: Allow non parent devices to be used for ZC DMA To: Mina Almasry Cc: Dragos Tatulea , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Saeed Mahameed , tariqt@nvidia.com, cratiu@nvidia.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250702172433.1738947-1-dtatulea@nvidia.com> <20250702172433.1738947-2-dtatulea@nvidia.com> <32cb77d8-a4a5-4fc7-a427-d723e60efc59@gmail.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 7/8/25 15:10, Mina Almasry wrote: > On Tue, Jul 8, 2025 at 4:05 AM Pavel Begunkov wrote: >> >> On 7/2/25 18:24, Dragos Tatulea wrote: >>> For zerocopy (io_uring, devmem), there is an assumption that the >>> parent device can do DMA. However that is not always the case: >>> for example mlx5 SF devices have an auxiliary device as a parent. >>> >>> This patch introduces the possibility for the driver to specify >>> another DMA device to be used via the new dma_dev field. The field >>> should be set before register_netdev(). >>> >>> A new helper function is added to get the DMA device or return NULL. >>> The callers can check for NULL and fail early if the device is >>> not capable of DMA. >>> >>> Signed-off-by: Dragos Tatulea >>> --- >>> include/linux/netdevice.h | 13 +++++++++++++ >>> 1 file changed, 13 insertions(+) >>> >>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h >>> index 5847c20994d3..83faa2314c30 100644 >>> --- a/include/linux/netdevice.h >>> +++ b/include/linux/netdevice.h >>> @@ -2550,6 +2550,9 @@ struct net_device { >>> >>> struct hwtstamp_provider __rcu *hwprov; >>> >>> + /* To be set by devices that can do DMA but not via parent. */ >>> + struct device *dma_dev; >>> + >>> u8 priv[] ____cacheline_aligned >>> __counted_by(priv_len); >>> } ____cacheline_aligned; >>> @@ -5560,4 +5563,14 @@ extern struct net_device *blackhole_netdev; >>> atomic_long_add((VAL), &(DEV)->stats.__##FIELD) >>> #define DEV_STATS_READ(DEV, FIELD) atomic_long_read(&(DEV)->stats.__##FIELD) >>> >>> +static inline struct device *netdev_get_dma_dev(const struct net_device *dev) >>> +{ >>> + struct device *dma_dev = dev->dma_dev ? dev->dma_dev : dev->dev.parent; >>> + >>> + if (!dma_dev->dma_mask) >> >> dev->dev.parent is NULL for veth and I assume other virtual devices as well. >> >> Mina, can you verify that devmem checks that? Seems like veth is rejected >> by netdev_need_ops_lock() in netdev_nl_bind_rx_doit(), but IIRC per netdev >> locking came after devmem got merged, and there are other virt devices that >> might already be converted. >> > > We never attempt devmem binding on any devices that don't support the > queue API, even before the per netdev locking was merged (there was an > explicit ops check). great! io_uring doesn't look at ->queue_mgmt_ops, so the helper from this patch needs to handle it one way or another. -- Pavel Begunkov