From patchwork Wed Jun 22 12:04:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robin Murphy X-Patchwork-Id: 12890593 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B847C43334 for ; Wed, 22 Jun 2022 12:04:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353714AbiFVMEV (ORCPT ); Wed, 22 Jun 2022 08:04:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234992AbiFVMES (ORCPT ); Wed, 22 Jun 2022 08:04:18 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 8C37D3DA53; Wed, 22 Jun 2022 05:04:17 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5D0EF13D5; Wed, 22 Jun 2022 05:04:17 -0700 (PDT) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 33AA83F534; Wed, 22 Jun 2022 05:04:16 -0700 (PDT) From: Robin Murphy To: alex.williamson@redhat.com, cohuck@redhat.com Cc: kvm@vger.kernel.org, iommu@lists.linux.dev, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, jgg@nvidia.com Subject: [PATCH v2 1/2] vfio/type1: Simplify bus_type determination Date: Wed, 22 Jun 2022 13:04:11 +0100 Message-Id: X-Mailer: git-send-email 2.36.1.dirty MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Since IOMMU groups are mandatory for drivers to support, it stands to reason that any device which has been successfully be added to a group must be on a bus supported by that IOMMU driver, and therefore a domain viable for any device in the group must be viable for all devices in the group. This already has to be the case for the IOMMU API's internal default domain, for instance. Thus even if the group contains devices on different buses, that can only mean that the IOMMU driver actually supports such an odd topology, and so without loss of generality we can expect the bus type of any device in a group to be suitable for IOMMU API calls. Replace vfio_bus_type() with a simple call to resolve an appropriate member device from which to then derive a bus type. This is also a step towards removing the vague bus-based interfaces from the IOMMU API, when we can subsequently switch to using this device directly. Furthermore, scrutiny reveals a lack of protection for the bus being removed while vfio_iommu_type1_attach_group() is using it; the reference that VFIO holds on the iommu_group ensures that data remains valid, but does not prevent the group's membership changing underfoot. Holding the vfio_device for as long as we need here also neatly solves this. Signed-off-by: Robin Murphy Reviewed-by: Lu Baolu Reported-by: kernel test robot --- After sleeping on it, I decided to type up the helper function approach to see how it looked in practice, and in doing so realised that with one more tweak it could also subsume the locking out of the common paths as well, so end up being a self-contained way for type1 to take care of its own concern, which I rather like. drivers/vfio/vfio.c | 18 +++++++++++++++++- drivers/vfio/vfio.h | 3 +++ drivers/vfio/vfio_iommu_type1.c | 30 +++++++++++------------------- 3 files changed, 31 insertions(+), 20 deletions(-) diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 61e71c1154be..73bab04880d0 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -448,7 +448,7 @@ static void vfio_group_get(struct vfio_group *group) * Device objects - create, release, get, put, search */ /* Device reference always implies a group reference */ -static void vfio_device_put(struct vfio_device *device) +void vfio_device_put(struct vfio_device *device) { if (refcount_dec_and_test(&device->refcount)) complete(&device->comp); @@ -475,6 +475,22 @@ static struct vfio_device *vfio_group_get_device(struct vfio_group *group, return NULL; } +struct vfio_device *vfio_device_get_from_iommu(struct iommu_group *iommu_group) +{ + struct vfio_group *group = vfio_group_get_from_iommu(iommu_group); + struct vfio_device *device; + + mutex_lock(&group->device_lock); + list_for_each_entry(device, &group->device_list, group_next) { + if (vfio_device_try_get(device)) { + mutex_unlock(&group->device_lock); + return device; + } + } + mutex_unlock(&group->device_lock); + return NULL; +} + /* * VFIO driver API */ diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h index a67130221151..e8f21e64541b 100644 --- a/drivers/vfio/vfio.h +++ b/drivers/vfio/vfio.h @@ -70,3 +70,6 @@ struct vfio_iommu_driver_ops { int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops); void vfio_unregister_iommu_driver(const struct vfio_iommu_driver_ops *ops); + +struct vfio_device *vfio_device_get_from_iommu(struct iommu_group *iommu_group); +void vfio_device_put(struct vfio_device *device); diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index c13b9290e357..e38b8bfde677 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -1679,18 +1679,6 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, return ret; } -static int vfio_bus_type(struct device *dev, void *data) -{ - struct bus_type **bus = data; - - if (*bus && *bus != dev->bus) - return -EINVAL; - - *bus = dev->bus; - - return 0; -} - static int vfio_iommu_replay(struct vfio_iommu *iommu, struct vfio_domain *domain) { @@ -2159,7 +2147,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, struct vfio_iommu *iommu = iommu_data; struct vfio_iommu_group *group; struct vfio_domain *domain, *d; - struct bus_type *bus = NULL; + struct vfio_device *iommu_api_dev; bool resv_msi, msi_remap; phys_addr_t resv_msi_base = 0; struct iommu_domain_geometry *geo; @@ -2192,18 +2180,19 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, goto out_unlock; } - /* Determine bus_type in order to allocate a domain */ - ret = iommu_group_for_each_dev(iommu_group, &bus, vfio_bus_type); - if (ret) + /* Resolve the group back to a member device for IOMMU API ops */ + ret = -ENODEV; + iommu_api_dev = vfio_device_get_from_iommu(iommu_group); + if (!iommu_api_dev) goto out_free_group; ret = -ENOMEM; domain = kzalloc(sizeof(*domain), GFP_KERNEL); if (!domain) - goto out_free_group; + goto out_put_dev; ret = -EIO; - domain->domain = iommu_domain_alloc(bus); + domain->domain = iommu_domain_alloc(iommu_api_dev->dev->bus); if (!domain->domain) goto out_free_domain; @@ -2258,7 +2247,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, list_add(&group->next, &domain->group_list); msi_remap = irq_domain_check_msi_remap() || - iommu_capable(bus, IOMMU_CAP_INTR_REMAP); + iommu_capable(iommu_api_dev->dev->bus, IOMMU_CAP_INTR_REMAP); if (!allow_unsafe_interrupts && !msi_remap) { pr_warn("%s: No interrupt remapping support. Use the module param \"allow_unsafe_interrupts\" to enable VFIO IOMMU support on this platform\n", @@ -2331,6 +2320,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, iommu->num_non_pinned_groups++; mutex_unlock(&iommu->lock); vfio_iommu_resv_free(&group_resv_regions); + vfio_device_put(iommu_api_dev); return 0; @@ -2342,6 +2332,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data, vfio_iommu_resv_free(&group_resv_regions); out_free_domain: kfree(domain); +out_put_dev: + vfio_device_put(iommu_api_dev); out_free_group: kfree(group); out_unlock: