From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5A5B7341ADD; Wed, 17 Jun 2026 09:41:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781689278; cv=none; b=LSdR78ClQXqAJvIGlub0pRLSssuf71a8rd/J5d3Lgqpqqd2x0GnCE4q1F+ycouR2MEFTtmyrP4qo0S28ak+3f/DW+67rfA3uTs+v9qg5pYRrDEnrIhQ6w6tFWmPPkI7O801tgRmWitpWhQlWmdNfWzkuRQVPkOt8Y+kbxcdgzvE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781689278; c=relaxed/simple; bh=mdpARkk5ZHpUYutdupMFuTRX/LVTrPMR7KpYge5m8nQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OXuwujs/zYovi3TN8HPx/mRoEA8F1tOIESK669+IHhr5CxL29KIGx6kcJ1riqmKLlH9TTHwEn99zOtkrwI68poOpm+KoqJ6EkmMevms40JAjHttppgYzAODIQBTIfDb4JDO1bfj4GgKYDdZvOBxY7p8Ezy7aMOJ/PgNkeSU47z8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UlEN7Amy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UlEN7Amy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 825261F000E9; Wed, 17 Jun 2026 09:41:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781689277; bh=cyKgowJd1zhtu0qWQyFQH6H6T62iAG8kuM8i9z4Jxjk=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=UlEN7AmyCCwaO+J4i9oamPtHdmVZ6G0/gAGSRwLuRjaagQs3lDyxjk40lSgbur3hB ylJRSbuW1A1cPyPN9tYZJPoSQzq9LcbTWtTFGkbKSKME6t3BZYZZJlR9/lch7zX+YF 4qfkae6Io7Ss1TUNmFMfh8nEB/bc5CFmE1WdLKGm1e9SpT/ofui5QQl5xl48ReHTZn oci5C/Nm9/58vLwrHWdwLln5QtUn5tSZ5sNYyoXLf2RGAIPj4eMefrg4HsQzVlw66F TDGCdcXWGqTNVrifsQBICrLvQQeV694Aew79tmUlE4mtNRRKtA9oIh3VYrDCVIba6b vAfUZLXMq+mmQ== Date: Wed, 17 Jun 2026 12:41:13 +0300 From: Leon Romanovsky To: Zhiping Zhang Cc: Jason Gunthorpe , 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 v8 2/4] dma-buf: add optional get_pci_tph() callback Message-ID: <20260617094113.GU327369@unreal> References: <20260615065912.2177918-1-zhipingz@meta.com> <20260615065912.2177918-3-zhipingz@meta.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: <20260615065912.2177918-3-zhipingz@meta.com> On Sun, Jun 14, 2026 at 11:58:59PM -0700, Zhiping Zhang wrote: > Add an optional dma_buf_ops.get_pci_tph callback and a > DMA-buf importer wrapper, dma_buf_get_pci_tph(). > > TPH is PCIe TLP Processing Hint. 8-bit ST and 16-bit Extended ST are > distinct PCIe TPH namespaces, so the importer requests the namespace it > can emit and the exporter returns the matching ST/PH tuple or > -EOPNOTSUPP. > > dma_buf_get_pci_tph() is the importer entry point. It requires > &dmabuf->resv to be held while the callback runs and returns > -EOPNOTSUPP when the exporter does not provide PCI TPH metadata. > > The first user is VFIO_DEVICE_FEATURE_DMA_BUF_TPH in vfio-pci, with > mlx5 as the first importer. > > Signed-off-by: Zhiping Zhang > --- > drivers/dma-buf/dma-buf.c | 25 +++++++++++++++++++++++++ > include/linux/dma-buf.h | 16 ++++++++++++++++ > 2 files changed, 41 insertions(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index d504c636dc29..7a4c9b0d5dab 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -1144,6 +1144,31 @@ void dma_buf_unpin(struct dma_buf_attachment *attach) > } > EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, "DMA_BUF"); > > +/** > + * dma_buf_get_pci_tph - Retrieve PCIe TLP Processing Hint (TPH) metadata > + * @dmabuf: DMA buffer to query > + * @extended: false for 8-bit ST, true for 16-bit Extended ST > + * @steering_tag: returns the raw steering tag for the requested namespace > + * @ph: returns the TPH processing hint > + * > + * Wrapper for the optional &dma_buf_ops.get_pci_tph callback. > + * > + * Must be called with &dma_buf.resv held. Returns -EOPNOTSUPP if the > + * exporter does not implement the callback or has no metadata for the > + * requested namespace. > + */ > +int dma_buf_get_pci_tph(struct dma_buf *dmabuf, bool extended, > + u16 *steering_tag, u8 *ph) > +{ > + dma_resv_assert_held(dmabuf->resv); > + > + if (!dmabuf->ops->get_pci_tph) > + return -EOPNOTSUPP; > + > + return dmabuf->ops->get_pci_tph(dmabuf, extended, steering_tag, ph); > +} > +EXPORT_SYMBOL_NS_GPL(dma_buf_get_pci_tph, "DMA_BUF"); > + > /** > * dma_buf_map_attachment - Returns the scatterlist table of the attachment; > * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index d1203da56fc5..5e7b69a40f3d 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -113,6 +113,20 @@ struct dma_buf_ops { > */ > void (*unpin)(struct dma_buf_attachment *attach); > > + /** > + * @get_pci_tph: There should be a blank line after the line above, along with a clear and concise description of what this callback does. Thanks > + * @dmabuf: DMA buffer for which to retrieve TPH metadata > + * @extended: false for 8-bit ST, true for 16-bit Extended ST > + * @steering_tag: Returns the raw TPH steering tag for the requested > + * namespace > + * @ph: Returns the TPH processing hint (2-bit value) > + * > + * Optional callback for dma_buf_get_pci_tph(). Called with > + * &dma_buf.resv held. > + */ > + int (*get_pci_tph)(struct dma_buf *dmabuf, bool extended, > + u16 *steering_tag, u8 *ph); > + > /** > * @map_dma_buf: > * > @@ -563,6 +577,8 @@ void dma_buf_detach(struct dma_buf *dmabuf, > struct dma_buf_attachment *attach); > int dma_buf_pin(struct dma_buf_attachment *attach); > void dma_buf_unpin(struct dma_buf_attachment *attach); > +int dma_buf_get_pci_tph(struct dma_buf *dmabuf, bool extended, > + u16 *steering_tag, u8 *ph); > > struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info); > > -- > 2.53.0-Meta >