vfio: If an IOMMU backend fails, keep looking (7c435b46) · Commits · 戴 / test

Consider an IOMMU to be an API rather than an implementation, we might have multiple implementations supporting the same API, so try another if one fails. The expectation here is that we'll really only have one implementation per device type. For instance the existing type1 driver works with any PCI device where the IOMMU API is available. A vGPU vendor may have a virtual PCI device which provides DMA isolation and mapping through other mechanisms, but can re-use userspaces that make use of the type1 VFIO IOMMU API. This allows that to work. Signed-off-by:

Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -1080,30 +1080,26 @@ static long vfio_ioctl_set_iommu(struct vfio_container *container,
		continue;
		}

		/* module reference holds the driver we're working on */
		mutex_unlock(&vfio.iommu_drivers_lock);

		data = driver->ops->open(arg);
		if (IS_ERR(data)) {
		ret = PTR_ERR(data);
		module_put(driver->ops->owner);
		goto skip_drivers_unlock;
		continue;
		}

		ret = __vfio_container_attach_groups(container, driver, data);
		if (!ret) {
		container->iommu_driver = driver;
		container->iommu_data = data;
		} else {
		if (ret) {
		driver->ops->release(data);
		module_put(driver->ops->owner);
		continue;
		}

		goto skip_drivers_unlock;
		container->iommu_driver = driver;
		container->iommu_data = data;
		break;
		}

		mutex_unlock(&vfio.iommu_drivers_lock);
		skip_drivers_unlock:
		up_write(&container->group_lock);

		return ret;

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