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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8ac849e35afsm159006516d6.3.2026.04.14.08.11.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 08:11:26 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wCfQD-0000000BNfx-2aVf; Tue, 14 Apr 2026 12:11:25 -0300 Date: Tue, 14 Apr 2026 12:11:25 -0300 From: Jason Gunthorpe To: fengchengwen Cc: Leon Romanovsky , Bjorn Helgaas , linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Keith Busch , Yochai Cohen , Yishai Hadas , Zhiping Zhang Subject: Re: [RFC] Proposal: Add sysfs interface for PCIe TPH Steering Tag retrieval and configuration Message-ID: <20260414151125.GF2577880@ziepe.ca> 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> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <11eaea26-ec10-264a-db1e-951f6b46078d@huawei.com> 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. Jason