From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: [PATCH/RFC 2/6] vfio: Ignore real IOMMUs if CONFIG_VFIO_NOIOMMU=y Date: Fri, 9 Feb 2018 16:16:49 +0100 Message-ID: <1518189413-2761-3-git-send-email-geert+renesas@glider.be> References: <1518189413-2761-1-git-send-email-geert+renesas@glider.be> Cc: Arnd Bergmann , Alexander Graf , Magnus Damm , Laurent Pinchart , Wolfram Sang , kvm@vger.kernel.org, linux-renesas-soc@vger.kernel.org, qemu-devel@nongnu.org, Geert Uytterhoeven To: Baptiste Reynal , Alex Williamson Return-path: Received: from baptiste.telenet-ops.be ([195.130.132.51]:38714 "EHLO baptiste.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751099AbeBIPRL (ORCPT ); Fri, 9 Feb 2018 10:17:11 -0500 In-Reply-To: <1518189413-2761-1-git-send-email-geert+renesas@glider.be> Sender: kvm-owner@vger.kernel.org List-ID: Allow use of the No-IOMMU mode even if a real IOMMU is present. This is useful in case the device is not part of an actual IOMMU group. Not-Signed-off-by: Geert Uytterhoeven --- Question: - Some devices (e.g. rcar-gpio) don't use DMA, so why do they need an IOMMU group? - Even devices using DMA may do so using a separate DMAC module, pointed to by "dmas" DT properties (e.g. sh-sci), hence they may be not part of an IOMMU group. - How to know which devices do DMA? --- drivers/vfio/vfio.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 2bc3705a99bd2f1a..7736c3fbe468a3da 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -129,9 +129,13 @@ struct iommu_group *vfio_iommu_group_get(struct device *dev) * bus. We set iommudata simply to be able to identify these groups * as special use and for reclamation later. */ - if (group || !noiommu || iommu_present(dev->bus)) + if (group || !noiommu) return group; + if (iommu_present(dev->bus)) + dev_warn(dev, "iommu present (%ps), ignoring\n", + dev->bus->iommu_ops); + group = iommu_group_alloc(); if (IS_ERR(group)) return NULL; -- 2.7.4