From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout07.his.huawei.com (canpmsgout07.his.huawei.com [113.46.200.222]) (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 17C5D1A2545; Wed, 15 Apr 2026 01:47:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.222 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776217676; cv=none; b=udnJlLLUMdISgXmGhmRkPUwev1INcDwd0fFjQoPlHyu0lBie0ANrJ4dD/Lz4ubWlfE/u9EX+ofCdaekykXV/bYKzRD8KEX1iYlJ4CVRW5Aj/mM4YePHAwDV00/amxYsGgrujK3O1wO7nZfaVgp/itmHrHifkZzj3YQNwbcLwR6Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776217676; c=relaxed/simple; bh=E0hei9H/2peq0vRfhtKbeuGrksJf/kZKlMZyfM4sk0o=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=szl76GoByjMp/w6EOADtf8ZYd85ryITbOWRizwWGycbaIbUXFjW5Eluw+R/nrqcEZbE8C0K+MBSTbcLI1FM2iBH85L14q37qGQsXEi51JRwmBUGs9u1aluab6W+VB8Nz9amtcb0GUAOzwXC9cppEX7ycOnGL9kdJR4x/xH5AxbQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=xLjXOP53; arc=none smtp.client-ip=113.46.200.222 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="xLjXOP53" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=FKRdkwMjOaJ50cZQVCsjgPQXyq1PmmPA+TconZgAAI4=; b=xLjXOP53NN9FcwooK7x1IrxXikyHDczrsdyivuYn9Orevo4EtcIBcm+uyFpOdliAshfavswN/ W85houPnKWrTLdJe2iNWA+kSOhiffrq3D3EGt2AZGMo50leaBOHZCzwwWnMH1D3L48OZh5vGHpH aflpVvibp0IPSuWx0P/oWY4= Received: from mail.maildlp.com (unknown [172.19.163.163]) by canpmsgout07.his.huawei.com (SkyGuard) with ESMTPS id 4fwP4l3jDXzLlSv; Wed, 15 Apr 2026 09:41:27 +0800 (CST) Received: from kwepemk500009.china.huawei.com (unknown [7.202.194.94]) by mail.maildlp.com (Postfix) with ESMTPS id DC9304048B; Wed, 15 Apr 2026 09:47:44 +0800 (CST) Received: from [10.67.121.161] (10.67.121.161) by kwepemk500009.china.huawei.com (7.202.194.94) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 15 Apr 2026 09:47:44 +0800 Message-ID: <9a7609b7-1d8d-4758-8f3b-081658d90711@huawei.com> Date: Wed, 15 Apr 2026 09:47:43 +0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] Proposal: Add sysfs interface for PCIe TPH Steering Tag retrieval and configuration To: Jason Gunthorpe CC: Leon Romanovsky , Bjorn Helgaas , , , , , Keith Busch , Yochai Cohen , Yishai Hadas , Zhiping Zhang References: <6ea4c4c2-774e-aa76-3665-918e2a24cc84@huawei.com> <20260413100152.GG21470@unreal> <20260413191930.GP21470@unreal> <20260414085723.GR21470@unreal> <84bf119e-fa8c-4c97-9197-3377b7e2b250@huawei.com> <20260414103547.GA361495@unreal> <11eaea26-ec10-264a-db1e-951f6b46078d@huawei.com> <20260414151125.GF2577880@ziepe.ca> Content-Language: en-US From: fengchengwen In-Reply-To: <20260414151125.GF2577880@ziepe.ca> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems500002.china.huawei.com (7.221.188.17) To kwepemk500009.china.huawei.com (7.202.194.94) On 4/14/2026 11:11 PM, Jason Gunthorpe wrote: > On Tue, Apr 14, 2026 at 10:46:00PM +0800, fengchengwen wrote: >> We have a real platform requirement: >> >> * 1. Devices in TPH Device-Specific Mode with no standard ST table >> * 2. Steering Tags must be obtained from ACPI _DSM (kernel-only) >> * 3. Devices are fully managed by userspace drivers (VFIO/UIO) >> * 4. Userspace must program STs into vendor-specific registers > > No, this is nonsenscial too. > > If you want to control the steering tags for MMIO BAR memory exposed > by VFIO then the DMABUF mechanism Keith & co has been working on is > the correct approach. > > If the VFIO user needs to control steering tags for the device it is > directly controling then it must do that through VFIO ioctls. > > Nobody messes around with other devices under the covers of the > operating kernel driver. Stop proposing that. Understood. For VFIO-passed devices that are fully under userspace control, we will implement the TPH Steering Tag query interface exclusively through VFIO ioctls, not sysfs. This will allow userspace to query per-CPU Steering Tags from platform firmware (ACPI _DSM) for the VFIO device, which is fully under its control. Thanks > > Jason