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Wed, 23 Sep 2020 02:32:49 -0400 X-MC-Unique: OsAsDADyNyWgWEaMZInWBA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BD408807100; Wed, 23 Sep 2020 06:32:47 +0000 (UTC) Received: from [10.36.112.29] (ovpn-112-29.ams2.redhat.com [10.36.112.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4694B78822; Wed, 23 Sep 2020 06:32:45 +0000 (UTC) Subject: Re: [PATCH v2] iommu/arm: Add module parameter to set msi iova address To: Will Deacon , Vennila Megavannan References: <20200914181307.117792-1-vemegava@linux.microsoft.com> <20200921204545.GA3811@willie-the-truck> From: Auger Eric Message-ID: <85f7d1ae-71a9-4e95-8a30-03cc699d4794@redhat.com> Date: Wed, 23 Sep 2020 08:32:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200921204545.GA3811@willie-the-truck> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Cc: jean-philippe@linaro.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, tyhicks@linux.microsoft.com, srinath.mannam@broadcom.com, bcm-kernel-feedback-list@broadcom.com, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Will, On 9/21/20 10:45 PM, Will Deacon wrote: > On Mon, Sep 14, 2020 at 11:13:07AM -0700, Vennila Megavannan wrote: >> From: Srinath Mannam >> >> Add provision to change default value of MSI IOVA base to platform's >> suitable IOVA using module parameter. The present hardcoded MSI IOVA base >> may not be the accessible IOVA ranges of platform. >> >> If any platform has the limitaion to access default MSI IOVA, then it can >> be changed using "arm-smmu.msi_iova_base=0xa0000000" command line argument. >> >> Signed-off-by: Srinath Mannam >> Co-developed-by: Vennila Megavannan >> Signed-off-by: Vennila Megavannan >> --- >> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 5 ++++- >> drivers/iommu/arm/arm-smmu/arm-smmu.c | 5 ++++- >> 2 files changed, 8 insertions(+), 2 deletions(-) > > This feels pretty fragile. Wouldn't it be better to realise that there's > a region conflict with iommu_dma_get_resv_regions() and move the MSI window > accordingly at runtime? Since cd2c9fcf5c66 ("iommu/dma: Move PCI window region reservation back into dma specific path"), the PCI host bridge windows are not exposed by iommu_dma_get_resv_regions() anymore. If I understood correctly, what is attempted here is to avoid the collision between such PCI host bridge window and the MSI IOVA range. Thanks Eric > > Will > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu