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Thu, 16 Jul 2026 07:47:08 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wkNMi-00000002Yhx-0bks; Thu, 16 Jul 2026 11:47:08 -0300 Date: Thu, 16 Jul 2026 11:47:08 -0300 From: Jason Gunthorpe To: fengchengwen Cc: Zhiping Zhang , Leon Romanovsky , Michael Guralnik , Sumit Semwal , Christian Konig , Alex Williamson , Bjorn Helgaas , kvm@vger.kernel.org, linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH v12 0/4] vfio/dma-buf: add TPH support for peer-to-peer access Message-ID: <20260716144708.GD210048@ziepe.ca> References: <20260715204008.3911275-1-zhipingz@meta.com> <7dd5c995-a23c-4d3a-9ba0-7fc77972339f@huawei.com> Precedence: bulk X-Mailing-List: kvm@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: <7dd5c995-a23c-4d3a-9ba0-7fc77972339f@huawei.com> On Thu, Jul 16, 2026 at 09:07:35AM +0800, fengchengwen wrote: > Because cross-Root-Port P2P traffic with ST does not affect the host, but > merely the completer may experience some performance degradation because > it lacks the TPH hint. In this case, I suggest adding restrictions in the > uAPI. I don't think this is complexity is worth doing for something that has no functional impact. There is no difference between supplying the TPH and not supplying it, so may as well supply it. Jason