From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752145AbdLAKjR (ORCPT ); Fri, 1 Dec 2017 05:39:17 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:39018 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbdLAKjP (ORCPT ); Fri, 1 Dec 2017 05:39:15 -0500 Date: Fri, 1 Dec 2017 10:39:43 +0000 From: Lorenzo Pieralisi To: Feng Kan Cc: "linux-acpi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Will Deacon , Hanjun Guo , Jon Masters , Robert Moore , Robin Murphy , Zhang Rui , "Rafael J. Wysocki" , Nate Watterson Subject: Re: [PATCH v3 0/5] ACPI: DMA ranges management Message-ID: <20171201103943.GA25066@red-moon> References: <20170803123239.11359-1-lorenzo.pieralisi@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 30, 2017 at 04:43:00PM -0800, Feng Kan wrote: > On Wed, Nov 29, 2017 at 11:28 PM, Feng Kan wrote: > > On Thu, Aug 3, 2017 at 5:32 AM, Lorenzo Pieralisi > > wrote: > >> This patch series is v3 of a previous posting: > >> > >> v2->v3: > >> - Fixed DMA masks computation > >> - Fixed size computation overflow in acpi_dma_get_range() > >> > >> v1->v2: > >> - Reworked acpi_dma_get_range() flow and logs > >> - Added IORT named component address limits > >> - Renamed acpi_dev_get_resources() helper function > >> - Rebased against v4.13-rc3 > >> > >> v2: http://lkml.kernel.org/r/20170731152323.32488-1-lorenzo.pieralisi@arm.com > >> v1: http://lkml.kernel.org/r/20170720144517.32529-1-lorenzo.pieralisi@arm.com > >> > >> -- Original cover letter -- > >> > >> As reported in: > >> > >> http://lkml.kernel.org/r/CAL85gmA_SSCwM80TKdkZqEe+S1beWzDEvdki1kpkmUTDRmSP7g@mail.gmail.com > >> > >> the bus connecting devices to an IOMMU bus can be smaller in size than > >> the IOMMU input address bits which results in devices DMA HW bugs in > >> particular related to IOVA allocation (ie chopping of higher address > >> bits owing to system bus HW capabilities mismatch with the IOMMU). > >> > >> Fortunately this problem can be solved through an already present but never > >> used ACPI 6.2 firmware bindings (ie _DMA object) allowing to define the DMA > >> window for a specific bus in ACPI and therefore all upstream devices > >> connected to it. > >> > >> This small patch series enables _DMA parsing in ACPI core code and > >> use it in ACPI IORT code in order to detect DMA ranges for devices and > >> update their data structures to make them work with their related DMA > >> addressing restrictions. > >> > >> Cc: Will Deacon > >> Cc: Hanjun Guo > >> Cc: Feng Kan > >> Cc: Jon Masters > >> Cc: Robert Moore > >> Cc: Robin Murphy > >> Cc: Zhang Rui > >> Cc: "Rafael J. Wysocki" > >> > >> Lorenzo Pieralisi (5): > >> ACPICA: resource_mgr: Allow _DMA method in walk resources > >> ACPI: Make acpi_dev_get_resources() method agnostic > >> ACPI: Introduce DMA ranges parsing > >> ACPI: Make acpi_dma_configure() DMA regions aware > >> ACPI/IORT: Add IORT named component memory address limits > >> > >> drivers/acpi/acpica/rsxface.c | 7 ++-- > >> drivers/acpi/arm64/iort.c | 57 ++++++++++++++++++++++++++- > >> drivers/acpi/resource.c | 82 +++++++++++++++++++++++++++++--------- > >> drivers/acpi/scan.c | 91 +++++++++++++++++++++++++++++++++++++++---- > >> include/acpi/acnames.h | 1 + > >> include/acpi/acpi_bus.h | 2 + > >> include/linux/acpi.h | 8 ++++ > >> include/linux/acpi_iort.h | 5 ++- > >> 8 files changed, 219 insertions(+), 34 deletions(-) > >> > >> -- > >> 2.10.0 > >> > > Lorenzo: > > > > A network driver can use pci_set_dma_mask or its like to override what > > is done with this patch here. > > Which would result in iova allocation greater than the original _DMA > > aperture. Should we force > > the dma_set_mask to not change if an existing mask is already set? > > Let me clarify the question some more, in our system the IOMMU supports only > 42 bits of address. With your _DMA aperture patch, the initial dma_mask and > coherent_mask are correctly set by the code. However, the device driver can > set the dma_mask and coherent mask at a later point which over writes the > initial setting by your code. In which case, once the iova is exhausted with the > 32 bit address, it will start seeking more iova address via the > dma_limit. In this > case it would fail my system since the iommu.aperture_end is that of 48 bits > as derived from ias field in the SMMU. > > Should the dma_limit be the smallest of driver->dma_mask, iommu.aperture_end and > your _DMA aperture size via ACPI table? Rather than just the > driver->dma_mask and > iommu.aperture_end. This will ensure the smallest/correct aperture is used. IIUC Nate already reported this issue - I will sync with Robin to check the status of this thread: https://marc.info/?l=linux-acpi&m=150108156230455&w=2 Thanks, Lorenzo