From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anup Patel Subject: Re: [PATCH 1/5] iommu: Add capability IOMMU_CAP_BYPASS Date: Wed, 19 Jul 2017 16:49:00 +0530 Message-ID: References: <1500456838-18405-1-git-send-email-anup.patel@broadcom.com> <1500456838-18405-2-git-send-email-anup.patel@broadcom.com> <675744d3-b070-1245-6ebc-579c4b5f4a75@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <675744d3-b070-1245-6ebc-579c4b5f4a75@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Robin Murphy Cc: Will Deacon , Joerg Roedel , Baptiste Reynal , Alex Williamson , Scott Branden , Linux Kernel , Linux ARM Kernel , Linux IOMMU , kvm@vger.kernel.org, BCM Kernel Feedback List-Id: iommu@lists.linux-foundation.org On Wed, Jul 19, 2017 at 4:28 PM, Robin Murphy wrote: > On 19/07/17 10:33, Anup Patel wrote: >> Some of the IOMMUs (such as ARM SMMU) are capable of bypassing >> transactions for which no IOMMU domain is configured. >> >> This patch adds IOMMU_CAP_BYPASS which can be used by IOMMU >> drivers to advertise transation bypass capability of an IOMMU. > > Whatever the intended semantics of this are, I can't help thinking it > would be better served by allowing callers to explicitly allocate their > own IOMMU_DOMAIN_IDENTITY domains. That would also be useful for the > problem we have with legacy virtio devices behind real IOMMUs. We want to use VFIO no-IOMMU mode for FlexRM device but currently it does not allow on our SOC because IOMMU ops are registered for platform bus. Regards, Anup