From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BF944FEA830 for ; Wed, 25 Mar 2026 08:49:35 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3574310E821; Wed, 25 Mar 2026 08:49:35 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="ltb7Z1iY"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8917810E821 for ; Wed, 25 Mar 2026 08:49:33 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 50C8E40DF9; Wed, 25 Mar 2026 08:49:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DBF7C4CEF7; Wed, 25 Mar 2026 08:49:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774428573; bh=oWiu4XCakpEEWouFgjSkDQdwlQEePei3CI0lNENWLjQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ltb7Z1iYmSiPVmQYAbIrLOoN+Nr2Z+YdWmZOZaSTD/tsGAbbSQRbqSofeHb6qkCbh HKUW7VOg2Ihj0GIAPLLWBjynlKhsHh3Ys3KDc29Rem+kGcBhxtPhTWgQH2s4UvjB46 gz/mVcWtL9ytM4SfSAClINJgkRMfa7FQF0FvLbaDA1RbbtL3H2i5hOfKVAd/GhZh2M /BV3cQA1QnK0kpl2xBsgdzcQdJUI1J7mUw8J3yUnCIGH3oxndxR9uhWCd629HuDhsK r7tD79zZiypj5bDBgmOipZkFwp0QdNFlX71D9qbfujgxE19uX75sx/HMaKAn6au5kl 9EpfLDDNEDCJw== Date: Wed, 25 Mar 2026 10:25:34 +0200 From: Leon Romanovsky To: Zhiping Zhang Cc: Jason Gunthorpe , 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 , Bjorn Helgaas Subject: Re: [RFC v2 1/2] vfio: add callback to get tph info for dmabuf Message-ID: <20260325082534.GN814676@unreal> References: <20260324234615.3731237-1-zhipingz@meta.com> <20260324234615.3731237-2-zhipingz@meta.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260324234615.3731237-2-zhipingz@meta.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Mar 24, 2026 at 04:46:02PM -0700, Zhiping Zhang wrote: > This patch adds a callback to get the tph info on DMA buffer exporters. > The tph info includes both the steering tag and the process hint (ph). > > The steering tag and ph are encoded in the flags field of > vfio_device_feature_dma_buf instead of adding new fields to the uapi > struct, to preserve ABI compatibility. > > Signed-off-by: Zhiping Zhang > --- > drivers/vfio/pci/vfio_pci_dmabuf.c | 26 ++++++++++++++++++++++++-- > include/linux/dma-buf.h | 30 ++++++++++++++++++++++++++++++ > include/uapi/linux/vfio.h | 9 +++++++-- > 3 files changed, 61 insertions(+), 4 deletions(-) <...> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index bb7b89330d35..e2a8962641d2 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -1505,8 +1505,13 @@ struct vfio_region_dma_range { > struct vfio_device_feature_dma_buf { > __u32 region_index; > __u32 open_flags; > - __u32 flags; > - __u32 nr_ranges; > + __u32 flags; > +#define VFIO_DMABUF_FL_TPH (1U << 0) /* TPH info is present */ > +#define VFIO_DMABUF_TPH_PH_SHIFT 1 /* bits 1-2: PH (2-bit) */ > +#define VFIO_DMABUF_TPH_PH_MASK 0x6U > +#define VFIO_DMABUF_TPH_ST_SHIFT 16 /* bits 16-31: steering tag */ > +#define VFIO_DMABUF_TPH_ST_MASK 0xffff0000U This extension of flags is basically kills future extension of this struct for anything that includes TPH. Add new enum vfio_device_feature_dma_buf_flags { VFIO_DMABUF_FL_TPH = 1 << 0 } > + __u32 nr_ranges; add your "__u16 steering_tag" and "__u8 ph" fields here. > struct vfio_region_dma_range dma_ranges[] __counted_by(nr_ranges); > }; > > -- > 2.52.0 > >