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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	David Woodhouse <dwmw2@infradead.org>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	Joerg Roedel <joro@8bytes.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"llvm@lists.linux.dev" <llvm@lists.linux.dev>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Shuah Khan <shuah@kernel.org>,
	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	Tom Rix <trix@redhat.com>, Will Deacon <will@kernel.org>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	Chaitanya Kulkarni <chaitanyak@nvidia.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Daniel Jordan <daniel.m.jordan@oracle.com>,
	David Gibson <david@gibson.dropbear.id.au>,
	Eric Auger <eric.auger@redhat.com>,
	Eric Farman <farman@linux.ibm.com>,
	"Jason Wang" <jasowang@redhat.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	"Martins, Joao" <joao.m.martins@oracle.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Nicolin Chen <nicolinc@nvidia.com>,
	"Niklas Schnelle" <schnelle@linux.ibm.com>,
	Shameerali Kolothum Thodi  <shameerali.kolothum.thodi@huawei.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	Keqian Zhu <zhukeqian1@huawei.com>
Subject: RE: [PATCH v3 12/15] iommufd: Add kAPI toward external drivers for physical devices
Date: Sat, 5 Nov 2022 07:17:38 +0000	[thread overview]
Message-ID: <BN9PR11MB527617D35DE59BD0EF10F7098C3A9@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <12-v3-402a7d6459de+24b-iommufd_jgg@nvidia.com>

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Wednesday, October 26, 2022 2:12 AM
>
> +/**
> + * iommufd_device_bind - Bind a physical device to an iommu fd
> + * @ictx: iommufd file descriptor
> + * @dev: Pointer to a physical PCI device struct
> + * @id: Output ID number to return to userspace for this device
> + *
> + * A successful bind establishes an ownership over the device and returns
> + * struct iommufd_device pointer, otherwise returns error pointer.
> + *
> + * A driver using this API must set driver_managed_dma and must not touch
> + * the device until this routine succeeds and establishes ownership.
> + *
> + * Binding a PCI device places the entire RID under iommufd control.
> + *

Then what about non-PCI device? clearer to say that calling this interface
just places the entire physical device under iommufd control

> +	 * FIXME: This is conceptually broken for iommufd since we want to
> allow
> +	 * userspace to change the domains, eg switch from an identity IOAS
> to a
> +	 * DMA IOAs. There is currently no way to create a MSI window that

IOAs -> IOAS

> +		rc = iommu_get_msi_cookie(hwpt->domain, sw_msi_start);
> +		if (rc && rc != -ENODEV)
> +			return rc;

I know this is copied from VFIO but a comment is appreciated why
-ENODEV is considered sane to move forward.

> +	/*
> +	 * Otherwise the platform has a MSI window that is not isolated. For
> +	 * historical compat with VFIO allow a module parameter to ignore
> the
> +	 * insecurity.
> +	 */
> +	if (!(flags &
> IOMMUFD_ATTACH_FLAGS_ALLOW_UNSAFE_INTERRUPT))
> +		return -EPERM;

Throw out a warning similar to vfio.

> +
> +	rc = iopt_table_enforce_group_resv_regions(&hwpt->ioas->iopt,
> idev->dev,
> +						   idev->group,
> &sw_msi_start);
> +	if (rc)
> +		goto out_iova;

goto out_unlock since the function internally already called
__iopt_remove_reserved_iova() upon error.

> +	/*
> +	 * There is no differentiation when domains are allocated, so any
> domain
> +	 * that is willing to attach to the device is interchangeable with any
> +	 * other.
> +	 */
> +	mutex_lock(&ioas->mutex);
> +	list_for_each_entry(hwpt, &ioas->hwpt_list, hwpt_item) {
> +		if (!hwpt->auto_domain ||
> +		    !refcount_inc_not_zero(&hwpt->obj.users))

users cannot be zero at this point.

a new hwpt is added to the list with users==1 in attach.

detach first removes the hwpt and then decrement users.

Both are conducted by holding ioas->mutex.

> +			continue;
> +
> +		rc = iommufd_device_do_attach(idev, hwpt, flags);
> +		refcount_dec(&hwpt->obj.users);

with above I also wonder whether refcount_inc/dec are just
redundant here...

> +int iommufd_device_attach(struct iommufd_device *idev, u32 *pt_id,
> +			  unsigned int flags)
> +{
> +	struct iommufd_object *pt_obj;
> +	int rc;
> +
> +	pt_obj = iommufd_get_object(idev->ictx, *pt_id,
> IOMMUFD_OBJ_ANY);
> +	if (IS_ERR(pt_obj))
> +		return PTR_ERR(pt_obj);

Is there a reason why get_object() is not required for idev?

concurrent attach/unbind could lead to use-after-free here given users
for idev is added only in the end of the function.

> +
> +	switch (pt_obj->type) {
> +	case IOMMUFD_OBJ_HW_PAGETABLE: {
> +		struct iommufd_hw_pagetable *hwpt =
> +			container_of(pt_obj, struct iommufd_hw_pagetable,
> obj);
> +
> +		rc = iommufd_device_do_attach(idev, hwpt, flags);
> +		if (rc)
> +			goto out_put_pt_obj;
> +
> +		mutex_lock(&hwpt->ioas->mutex);
> +		list_add_tail(&hwpt->hwpt_item, &hwpt->ioas->hwpt_list);
> +		mutex_unlock(&hwpt->ioas->mutex);
> +		break;
> +	}
> +	case IOMMUFD_OBJ_IOAS: {
> +		struct iommufd_ioas *ioas =
> +			container_of(pt_obj, struct iommufd_ioas, obj);
> +
> +		rc = iommufd_device_auto_get_domain(idev, ioas, flags);
> +		if (rc)
> +			goto out_put_pt_obj;
> +		break;
> +	}
> +	default:
> +		rc = -EINVAL;
> +		goto out_put_pt_obj;
> +	}
> +
> +	refcount_inc(&idev->obj.users);
> +	*pt_id = idev->hwpt->obj.id;

What is the value of returning hwpt id of auto domain to user?

IMHO this will add more complexity to the life cycle of auto domain.

w/o allowing it the life cycle is simple i.e. the first attach which doesn't
find a matching domain creates a new auto domain then the last detach
frees it.

now if allowing user to populate auto domain similar to user-created
hwpt then detach also need get_object() to wait for concurrent
ioctls similar to iommufd_destroy() does and more trick on destroying
the object.

If no big gain probably hiding it from userspace is simpler?

> +void iommufd_device_detach(struct iommufd_device *idev)
> +{
> +	struct iommufd_hw_pagetable *hwpt = idev->hwpt;
> +
> +	mutex_lock(&hwpt->ioas->mutex);
> +	mutex_lock(&hwpt->devices_lock);
> +	list_del(&idev->devices_item);
> +	if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
> +		if (list_empty(&hwpt->devices)) {
> +			iopt_table_remove_domain(&hwpt->ioas->iopt,
> +						 hwpt->domain);
> +			list_del(&hwpt->hwpt_item);
> +		}
> +		iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->dev);

this is always required. not just for last device in a group.


  parent reply	other threads:[~2022-11-05  7:17 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-25 18:12 [PATCH v3 00/15] IOMMUFD Generic interface Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 01/15] iommu: Add IOMMU_CAP_ENFORCE_CACHE_COHERENCY Jason Gunthorpe
2022-10-26 12:45   ` Baolu Lu
2022-11-03  5:03   ` Tian, Kevin
2022-11-04 19:25     ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 02/15] iommu: Add device-centric DMA ownership interfaces Jason Gunthorpe
2022-11-03  5:11   ` Tian, Kevin
2022-11-04 19:32     ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 03/15] interval-tree: Add a utility to iterate over spans in an interval tree Jason Gunthorpe
2022-11-03  5:31   ` Tian, Kevin
2022-11-04 19:38     ` Jason Gunthorpe
2022-11-05  1:32       ` Tian, Kevin
2022-11-05  1:48       ` Matthew Wilcox
2022-11-07 14:38         ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 04/15] iommufd: Overview documentation Jason Gunthorpe
2022-10-26  4:17   ` Bagas Sanjaya
2022-10-28 19:09     ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 05/15] iommufd: File descriptor, context, kconfig and makefiles Jason Gunthorpe
2022-10-26 12:58   ` Baolu Lu
2022-10-26 17:14     ` Jason Gunthorpe
2022-10-29  3:43       ` Baolu Lu
2022-11-03  7:22   ` Tian, Kevin
2022-11-07 17:00     ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 06/15] kernel/user: Allow user::locked_vm to be usable for iommufd Jason Gunthorpe
2022-11-03  7:23   ` Tian, Kevin
2022-10-25 18:12 ` [PATCH v3 07/15] iommufd: PFN handling for iopt_pages Jason Gunthorpe
2022-11-01 19:38   ` Nicolin Chen
2022-11-02 13:13     ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 08/15] iommufd: Algorithms for PFN storage Jason Gunthorpe
2022-10-31 16:01   ` [PATCH v3 8/15] " Jason Gunthorpe
2022-11-01 16:09   ` Jason Gunthorpe
2022-11-03 20:08   ` Jason Gunthorpe
2022-11-04 16:26     ` Jason Gunthorpe
2022-11-04 16:04   ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 09/15] iommufd: Data structure to provide IOVA to PFN mapping Jason Gunthorpe
2022-10-26 18:46   ` [PATCH v3 9/15] " Jason Gunthorpe
2022-10-27 11:37   ` Jason Gunthorpe
2022-10-27 13:35   ` Jason Gunthorpe
2022-10-28 18:52   ` Jason Gunthorpe
2022-11-01 19:17   ` [PATCH v3 09/15] " Nicolin Chen
2022-11-02 13:11     ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 10/15] iommufd: IOCTLs for the io_pagetable Jason Gunthorpe
2022-10-26 17:01   ` Jason Gunthorpe
2022-10-26 23:17   ` Jason Gunthorpe
2022-10-29  7:25   ` Baolu Lu
2022-11-07 14:17     ` Jason Gunthorpe
2022-11-04  8:32   ` Tian, Kevin
2022-11-07 15:02     ` Jason Gunthorpe
2022-11-08  2:05       ` Tian, Kevin
2022-11-08 17:29         ` Jason Gunthorpe
2022-11-09  2:50           ` Tian, Kevin
2022-11-09 13:05             ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 11/15] iommufd: Add a HW pagetable object Jason Gunthorpe
2022-11-04 10:00   ` Tian, Kevin
2022-10-25 18:12 ` [PATCH v3 12/15] iommufd: Add kAPI toward external drivers for physical devices Jason Gunthorpe
2022-10-29  7:19   ` Baolu Lu
2022-11-07 14:14     ` Jason Gunthorpe
2022-11-05  7:17   ` Tian, Kevin [this message]
2022-11-07 17:54     ` Jason Gunthorpe
2022-11-08  2:17       ` Tian, Kevin
2022-10-25 18:12 ` [PATCH v3 13/15] iommufd: Add kAPI toward external drivers for kernel access Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 14/15] iommufd: vfio container FD ioctl compatibility Jason Gunthorpe
2022-10-27 14:12   ` Jason Gunthorpe
2022-11-01 19:45   ` Nicolin Chen
2022-11-02 13:15     ` Jason Gunthorpe
2022-11-05  0:07   ` Baolu Lu
2022-11-07 14:23     ` Jason Gunthorpe
2022-11-05  9:31   ` Tian, Kevin
2022-11-07 17:08     ` Jason Gunthorpe
2022-11-07 23:53       ` Tian, Kevin
2022-11-08  0:09         ` Jason Gunthorpe
2022-11-08  0:13           ` Tian, Kevin
2022-11-08  0:17             ` Jason Gunthorpe
2022-10-25 18:12 ` [PATCH v3 15/15] iommufd: Add a selftest Jason Gunthorpe
2022-11-01 20:32   ` Nicolin Chen
2022-11-02 13:17     ` Jason Gunthorpe
2022-11-02 18:49       ` Nathan Chancellor
2022-11-04  1:01   ` Jason Gunthorpe
2022-11-04  5:43     ` Tian, Kevin
2022-11-04 19:42       ` Jason Gunthorpe
2022-10-28 23:57 ` [PATCH v3 00/15] IOMMUFD Generic interface Nicolin Chen
2022-11-04 21:27 ` Alex Williamson
2022-11-04 22:03   ` Alex Williamson
2022-11-07 14:22     ` Jason Gunthorpe
2022-11-07 14:19   ` Jason Gunthorpe

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