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[84.226.106.126]) by smtp.gmail.com with ESMTPSA id j4sm9339398edq.13.2021.05.26.03.04.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 May 2021 03:04:21 -0700 (PDT) Date: Wed, 26 May 2021 12:04:03 +0200 From: Jean-Philippe Brucker To: "Rafael J. Wysocki" Cc: "Rafael J. Wysocki" , Len Brown , Joerg Roedel , "Michael S. Tsirkin" , Will Deacon , Catalin Marinas , Lu Baolu , David Woodhouse , ACPI Devel Maling List , "open list:AMD IOMMU (AMD-VI)" , virtualization@lists.linux-foundation.org, Linux ARM , Eric Auger , sebastien.boeuf@intel.com, Robin Murphy , kevin.tian@intel.com, Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla Subject: Re: [PATCH v2 3/6] ACPI: Add driver for the VIOT table Message-ID: References: <20210423113836.3974972-1-jean-philippe@linaro.org> <20210423113836.3974972-4-jean-philippe@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Fri, May 21, 2021 at 06:39:24PM +0200, Rafael J. Wysocki wrote: > > diff --git a/drivers/acpi/viot.c b/drivers/acpi/viot.c > > new file mode 100644 > > index 000000000000..710e5a5eac70 > > --- /dev/null > > +++ b/drivers/acpi/viot.c > > @@ -0,0 +1,350 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Virtual I/O topology > > In the first place, more information on what this is all about, please. > > What it does and how it is used. Sure, I can add: * * The Virtual I/O Translation Table (VIOT) describes the topology of * para-virtual IOMMUs and the endpoints they manage. The OS uses it to * initialize devices in the right order, preventing endpoints from * issuing DMA before their IOMMU is ready. * * When binding a driver to a device, before calling the device driver's * probe() method, the driver infrastructure calls dma_configure(). At * that point the VIOT driver looks for an IOMMU associated to the device * in the VIOT table. If an IOMMU exists and has been initialized, the * VIOT driver initializes the device's IOMMU fwspec, allowing the DMA * infrastructure to invoke the IOMMU ops when the device driver * configures DMA mappings. If an IOMMU exists and hasn't yet been * initialized, VIOT returns -EPROBE_DEFER to postpone probing the device * until the IOMMU is available. */ Thanks, Jean