From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D4BF67D07D; Tue, 30 Sep 2025 07:57:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759219074; cv=none; b=KvQ6NmYq+awl+IxbDe+G1D31Tix11F6CM/f/vLM/LuA+bvG26tvHs+wLWL49VI1qQWvz0B6ycusrdGM6r4XcJcI9Wyeu9cUt3AniuMSZG2MuRfoan2us11+M9WVgIa572BaYarYTfhyYRv27MH40w3ap/bVOJdJxN+8NaOKlQkQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759219074; c=relaxed/simple; bh=i3BtTTr7nZIJz33RyVUpfLlfxu4epWOssHy+VLrcscQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FNryZTMOREUpenBbTyZBZLuPwgBU+IJWtbAEVHEATQUGRgwQkm5CQrEouCeQvoXNkqTUCZH0zaLHzw22fwBq0MfenYPPn6iVjxfEnO80ddOZ/zm0PyAQhOzc1ni8lQIUQfnsiinHLc6r9RFaQtPlNLHUo2B1sbqD1fHrvnMcNzg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lKEnQkLh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lKEnQkLh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 879DEC4CEF0; Tue, 30 Sep 2025 07:57:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759219073; bh=i3BtTTr7nZIJz33RyVUpfLlfxu4epWOssHy+VLrcscQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lKEnQkLh/7QlrpMJsb5yRxE5AbBpzJMJNRvLELIbdmZqsMudIfJkl5IIjVlvWd45t 9CdHZPBwdsFyTXltr7C+E/ikvBD8M3GKILT1uJbM/dqVtkzxxeI95NEbtW/zrd+Ep5 UJKj7ByQ5cHM7iDUE5YdLldljkvDneKjj7T0/Jl4BAwLIv6rMPS82rffMeFvtqMlii rJtHqvVmDH+CUonBV/bnseaOumQHFjDS8yuzzqj15+2YNU8QWaz2EfS70aqZHG3yUz GrVG3wKTr88ok96rH2QGVO9OvriGTC+fSkO/DeP0k5odor2Iw88fzatiG+tDDQkt+a OH7f8EY3JlCxQ== Date: Tue, 30 Sep 2025 10:57:48 +0300 From: Leon Romanovsky To: Alex Williamson Cc: Jason Gunthorpe , Andrew Morton , Bjorn Helgaas , Christian =?iso-8859-1?Q?K=F6nig?= , dri-devel@lists.freedesktop.org, iommu@lists.linux.dev, Jens Axboe , Joerg Roedel , kvm@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Logan Gunthorpe , Marek Szyprowski , Robin Murphy , Sumit Semwal , Vivek Kasireddy , Will Deacon Subject: Re: [PATCH v4 07/10] vfio/pci: Add dma-buf export config for MMIO regions Message-ID: <20250930075748.GF324804@unreal> References: <20250929151740.21f001e3.alex.williamson@redhat.com> Precedence: bulk X-Mailing-List: linux-media@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: <20250929151740.21f001e3.alex.williamson@redhat.com> On Mon, Sep 29, 2025 at 03:17:40PM -0600, Alex Williamson wrote: > On Sun, 28 Sep 2025 17:50:17 +0300 > Leon Romanovsky wrote: > > > From: Leon Romanovsky > > > > Add new kernel config which indicates support for dma-buf export > > of MMIO regions, which implementation is provided in next patches. > > > > Signed-off-by: Leon Romanovsky > > --- > > drivers/vfio/pci/Kconfig | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig > > index 2b0172f54665..55ae888bf26a 100644 > > --- a/drivers/vfio/pci/Kconfig > > +++ b/drivers/vfio/pci/Kconfig > > @@ -55,6 +55,26 @@ config VFIO_PCI_ZDEV_KVM > > > > To enable s390x KVM vfio-pci extensions, say Y. > > > > +config VFIO_PCI_DMABUF > > + bool "VFIO PCI extensions for DMA-BUF" > > + depends on VFIO_PCI_CORE > > + depends on PCI_P2PDMA && DMA_SHARED_BUFFER > > + default y > > + help > > + Enable support for VFIO PCI extensions that allow exporting > > + device MMIO regions as DMA-BUFs for peer devices to access via > > + peer-to-peer (P2P) DMA. > > + > > + This feature enables a VFIO-managed PCI device to export a portion > > + of its MMIO BAR as a DMA-BUF file descriptor, which can be passed > > + to other userspace drivers or kernel subsystems capable of > > + initiating DMA to that region. > > + > > + Say Y here if you want to enable VFIO DMABUF-based MMIO export > > + support for peer-to-peer DMA use cases. > > + > > + If unsure, say N. > > + > > source "drivers/vfio/pci/mlx5/Kconfig" > > > > source "drivers/vfio/pci/hisilicon/Kconfig" > > This is only necessary if we think there's a need to build a kernel with > P2PDMA and VFIO_PCI, but not VFIO_PCI_DMABUF. Does that need really > exist? It is used to filter build of vfio_pci_dmabuf.c - drivers/vfio/pci/Makefile: vfio-pci-core-$(CONFIG_VFIO_PCI_DMABUF) += vfio_pci_dmabuf.o > > I also find it unusual to create the Kconfig before adding the > supporting code. Maybe this could be popped to the end or rolled into > the last patch if we decided to keep it. Thanks, It is leftover from previous version, I can squash it, but first we need to decide what to do with pcim_p2pdma_init() call, if it needs to be guarded or not. Thanks > > Alex > >