Re: [PATCH drm-misc-next v3 6/7] drm/gpuvm: generalize dma_resv/extobj handling and GEM validation

Danilo Krummrich
2023-09-13T15:16:58Z

On 9/13/23 16:26, Christian König wrote:
> Am 13.09.23 um 14:16 schrieb Danilo Krummrich:
>> As mentioned in a different mail thread, the reply is based on the assumption
>> that we don't support anything else than GPUVM updates from the IOCTL.
>
> I think that this assumption is incorrect.

Well, more precisely I should have said "don't support GPUVM updated from within
fence signaling critical sections". And looking at the code, that doesn't seem what
you're doing there.

>
> Vulkan is just once specific use case, but this here should probably be able to handle other use cases as well.
>
> Especially with HMM you get the requirement that you need to be able to invalidate GPUVM mappings without grabbing a reservation lock.

What do you mean with "invalidate GPUVM mappings" in this context? drm_gpuvm_bo_evict()
should only be called from a ttm_device_funcs::move\x0f callback, we should hold the dma-resv
lock there.

>
> See what the eviction lock in amdgpu is doing for example.

The eviction_lock seems to protect a VM state "evicting" of whether any BO that
is associated with the VM is currently evicting. At the same time amdgpu protects
the eviceted list of the VM with a different lock. So this seems to be entirely
unrelated. Tracking a "currently evicting" state is not part of the GPUVM
implementation currently and hence nothing would change for amdgpu there.

>
> Regards,
> Christian.
>
>>
>> On Wed, Sep 13, 2023 at 11:14:46AM +0200, Thomas Hellström wrote:
>>> Hi!
>>>
>>> On Wed, 2023-09-13 at 01:36 +0200, Danilo Krummrich wrote:
>>>> On Tue, Sep 12, 2023 at 09:23:08PM +0200, Thomas Hellström wrote:
>>>>> On 9/12/23 18:50, Danilo Krummrich wrote:
>>>>>> On Tue, Sep 12, 2023 at 06:20:32PM +0200, Thomas Hellström wrote:
>>>>>>> Hi, Danilo,
>>>>>>>
>>>>>>> On 9/9/23 17:31, Danilo Krummrich wrote:
>>>>>>>> So far the DRM GPUVA manager offers common infrastructure to
>>>>>>>> track GPU VA
>>>>>>>> allocations and mappings, generically connect GPU VA mappings
>>>>>>>> to their
>>>>>>>> backing buffers and perform more complex mapping operations
>>>>>>>> on the GPU VA
>>>>>>>> space.
>>>>>>>>
>>>>>>>> However, there are more design patterns commonly used by
>>>>>>>> drivers, which
>>>>>>>> can potentially be generalized in order to make the DRM GPUVA
>>>>>>>> manager
>>>>>>>> represent a basic GPU-VM implementation. In this context,
>>>>>>>> this patch aims
>>>>>>>> at generalizing the following elements.
>>>>>>>>
>>>>>>>> 1) Provide a common dma-resv for GEM objects not being used
>>>>>>>> outside of
>>>>>>>>       this GPU-VM.
>>>>>>>>
>>>>>>>> 2) Provide tracking of external GEM objects (GEM objects
>>>>>>>> which are
>>>>>>>>       shared with other GPU-VMs).
>>>>>>>>
>>>>>>>> 3) Provide functions to efficiently lock all GEM objects dma-
>>>>>>>> resv the
>>>>>>>>       GPU-VM contains mappings of.
>>>>>>>>
>>>>>>>> 4) Provide tracking of evicted GEM objects the GPU-VM
>>>>>>>> contains mappings
>>>>>>>>       of, such that validation of evicted GEM objects is
>>>>>>>> accelerated.
>>>>>>>>
>>>>>>>> 5) Provide some convinience functions for common patterns.
>>>>>>>>
>>>>>>>> Rather than being designed as a "framework", the target is to
>>>>>>>> make all
>>>>>>>> features appear as a collection of optional helper functions,
>>>>>>>> such that
>>>>>>>> drivers are free to make use of the DRM GPUVA managers basic
>>>>>>>> functionality and opt-in for other features without setting
>>>>>>>> any feature
>>>>>>>> flags, just by making use of the corresponding functions.
>>>>>>>>
>>>>>>>> Big kudos to Boris Brezillon for his help to figure out
>>>>>>>> locking for drivers
>>>>>>>> updating the GPU VA space within the fence signalling path.
>>>>>>>>
>>>>>>>> Suggested-by: Matthew Brost <matthew.brost@intel.com>
>>>>>>>> Signed-off-by: Danilo Krummrich <dakr@redhat.com>
>>>>>>>> ---
>>>>>>>>     drivers/gpu/drm/drm_gpuvm.c | 516
>>>>>>>> ++++++++++++++++++++++++++++++++++++
>>>>>>>>     include/drm/drm_gpuvm.h     | 197 ++++++++++++++
>>>>>>>>     2 files changed, 713 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/drm_gpuvm.c
>>>>>>>> b/drivers/gpu/drm/drm_gpuvm.c
>>>>>>>> index f4411047dbb3..8e62a043f719 100644
>>>>>>>> --- a/drivers/gpu/drm/drm_gpuvm.c
>>>>>>>> +++ b/drivers/gpu/drm/drm_gpuvm.c
>>>>>>>> @@ -73,6 +73,21 @@
>>>>>>>>      * &drm_gem_object list of &drm_gpuvm_bos for an existing
>>>>>>>> instance of this
>>>>>>>>      * particular combination. If not existent a new instance
>>>>>>>> is created and linked
>>>>>>>>      * to the &drm_gem_object.
>>>>>>>> + *
>>>>>>>> + * &drm_gpuvm_bo structures, since unique for a given
>>>>>>>> &drm_gpuvm, are also used
>>>>>>>> + * as entry for the &drm_gpuvm's lists of external and
>>>>>>>> evicted objects. Those
>>>>>>>> + * list are maintained in order to accelerate locking of
>>>>>>>> dma-resv locks and
>>>>>>>> + * validation of evicted objects bound in a &drm_gpuvm. For
>>>>>>>> instance the all
>>>>>>>> + * &drm_gem_object's &dma_resv of a given &drm_gpuvm can be
>>>>>>>> locked by calling
>>>>>>>> + * drm_gpuvm_exec_lock(). Once locked drivers can call
>>>>>>>> drm_gpuvm_validate() in
>>>>>>>> + * order to validate all evicted &drm_gem_objects. It is
>>>>>>>> also possible to lock
>>>>>>>> + * additional &drm_gem_objects by providing the
>>>>>>>> corresponding parameters to
>>>>>>>> + * drm_gpuvm_exec_lock() as well as open code the &drm_exec
>>>>>>>> loop while making
>>>>>>>> + * use of helper functions such as drm_gpuvm_prepare_range()
>>>>>>>> or
>>>>>>>> + * drm_gpuvm_prepare_objects().
>>>>>>>> + *
>>>>>>>> + * Every bound &drm_gem_object is treated as external object
>>>>>>>> when its &dma_resv
>>>>>>>> + * structure is different than the &drm_gpuvm's common
>>>>>>>> &dma_resv structure.
>>>>>>>>      */
>>>>>>>>     /**
>>>>>>>> @@ -420,6 +435,20 @@
>>>>>>>>      * Subsequent calls to drm_gpuvm_bo_obtain() for the same
>>>>>>>> &drm_gpuvm and
>>>>>>>>      * &drm_gem_object must be able to observe previous
>>>>>>>> creations and destructions
>>>>>>>>      * of &drm_gpuvm_bos in order to keep instances unique.
>>>>>>>> + *
>>>>>>>> + * The &drm_gpuvm's lists for keeping track of external and
>>>>>>>> evicted objects are
>>>>>>>> + * protected against concurrent insertion / removal and
>>>>>>>> iteration internally.
>>>>>>>> + *
>>>>>>>> + * However, drivers still need ensure to protect concurrent
>>>>>>>> calls to functions
>>>>>>>> + * iterating those lists, such as drm_gpuvm_validate() and
>>>>>>>> + * drm_gpuvm_prepare_objects(). Every such function contains
>>>>>>>> a particular
>>>>>>>> + * comment and lockdep checks if possible.
>>>>>>>> + *
>>>>>>>> + * Functions adding or removing entries from those lists,
>>>>>>>> such as
>>>>>>>> + * drm_gpuvm_bo_evict() or drm_gpuvm_bo_extobj_add() may be
>>>>>>>> called with external
>>>>>>>> + * locks being held, e.g. in order to avoid the
>>>>>>>> corresponding list to be
>>>>>>>> + * (safely) modified while potentially being iternated by
>>>>>>>> other API functions.
>>>>>>>> + * However, this is entirely optional.
>>>>>>>>      */
>>>>>>>>     /**
>>>>>>>> @@ -632,6 +661,131 @@
>>>>>>>>      *   }
>>>>>>>>      */
>>>>>>>> +/**
>>>>>>>> + * get_next_vm_bo_from_list() - get the next vm_bo element
>>>>>>>> + * @__gpuvm: The GPU VM
>>>>>>>> + * @__list_name: The name of the list we're iterating on
>>>>>>>> + * @__local_list: A pointer to the local list used to store
>>>>>>>> already iterated items
>>>>>>>> + * @__prev_vm_bo: The previous element we got from
>>>>>>>> drm_gpuvm_get_next_cached_vm_bo()
>>>>>>>> + *
>>>>>>>> + * This helper is here to provide lockless list iteration.
>>>>>>>> Lockless as in, the
>>>>>>>> + * iterator releases the lock immediately after picking the
>>>>>>>> first element from
>>>>>>>> + * the list, so list insertion deletion can happen
>>>>>>>> concurrently.
>>>>>>> Are the list spinlocks needed for that async state update from
>>>>>>> within the
>>>>>>> dma-fence critical section we've discussed previously?
>>>>>> Yes, but also for other reasons, see below.
>>>>>>
>>>>>>> Otherwise it should be sufficient to protect the lists with the
>>>>>>> gpuvm's resv
>>>>>>> (or for the extobj list with an outer lock).
>>>>>>>
>>>>>>> If those spinlocks are still needed in some situations, perhaps
>>>>>>> could we
>>>>>>> have an option to set them to NULL (Like IIRC the maple tree
>>>>>>> allows for)?
>>>>>> The evict spinlock is needed in any case, since in
>>>>>> drm_gpuvm_bo_evict() we're
>>>>>> holding only the dma-resv lock from the BO this function gets
>>>>>> called for. Hence,
>>>>>> the spinlock protects concurrent drm_gpuvm_bo_evict() calls with
>>>>>> different BOs.
>>>>> No. Only if you try to add external objects to the vm's evict list
>>>>> from
>>>>> within the evict code. That's not necessary since you loop through
>>>>> all
>>>>> external objects anyway when locking them so an "evicted" bool in
>>>>> the vm_bo,
>>>>> protected by the bo resv would be sufficient. The extobj locking
>>>>> loop can
>>>>> then add the bo to the evicted list.
>>>> And validate() can remove it while still holding all dma-resv locks,
>>>> neat!
>>>> However, what if two tasks are trying to lock the VA space
>>>> concurrently? What
>>>> do we do when the drm_gpuvm_bo's refcount drops to zero in
>>>> drm_gpuva_unlink()?
>>>> Are we guaranteed that at this point of time the drm_gpuvm_bo is not
>>>> on the
>>>> evicted list? Because otherwise we would call drm_gpuvm_bo_destroy()
>>>> with the
>>>> dma-resv lock held, which wouldn't be allowed, since
>>>> drm_gpuvm_bo_destroy()
>>>> might drop the last reference to the drm_gem_object and hence we'd
>>>> potentially
>>>> free the dma-resv lock while holding it, at least if it's an external
>>>> object.
>>> Easiest way in this scheme is to think of the lists as being protected
>>> by the vm's resv lock. That means anybody calling unlink() must also
>>> hold the vm's resv lock. (Which is OK from an UAF point of view, but
>>> perhaps not from a locking inversion POW from an async list update).
>> This would mean that on unlink() we'd need to hold the VM's resv lock and the
>> corresponding GEM's resv lock (in case they're not the same anyways) because the
>> VM's resv lock would protect the external / evicted object lists and the GEM
>> objects resv lock protects the GEM's list of drm_gpuvm_bos and the
>> drm_gpuvm_bo's list of drm_gpuvas.
>>
>>>>>> For extobjs an outer lock would be enough in case of Xe, but I
>>>>>> really would not
>>>>>> like to add even more complexity just to get the spinlock out of
>>>>>> the way in case
>>>>>> the driver already has an outer lock protecting this path.
>>>>> I must disagree here. These spinlocks and atomic operations are
>>>>> pretty
>>>>> costly and as discussed earlier this type of locking was the reason
>>>>> (at
>>>>> least according to the commit message) that made Christian drop the
>>>>> XArray
>>>>> use in drm_exec for the same set of objects: "The locking overhead
>>>>> is
>>>>> unecessary and measurable". IMHO the spinlock is the added
>>>>> complexity and a
>>>>> single wide lock following the drm locking guidelines set out by
>>>>> Daniel and
>>>>> David should really be the default choice with an opt-in for a
>>>>> spinlock if
>>>>> needed for async and pushing out to a wq is not an option.
>>>> For the external object list an outer lock would work as long as it's
>>>> not the
>>>> dma-resv lock of the corresponding GEM object, since here we actually
>>>> need to
>>>> remove the list entry from the external object list on
>>>> drm_gpuvm_bo_destroy().
>>>> It's just a bit weird design wise that drivers would need to take
>>>> this outer
>>>> lock on:
>>>>
>>>> - drm_gpuvm_bo_extobj_add()
>>>> - drm_gpuvm_bo_destroy()        (and hence also drm_gpuvm_bo_put())
>>>> - drm_gpuva_unlink()            (because it needs to call
>>>> drm_gpuvm_bo_put())
>>>> - drm_gpuvm_exec_lock()
>>>> - drm_gpuvm_exec_lock_array()
>>>> - drm_gpuvm_prepare_range()
>>>>
>>>> Given that it seems reasonable to do all the required locking
>>>> internally.
>>>  From a design POW, there has been a clear direction in XE to make
>>> things similar to mmap() / munmap(), so this outer lock, which in Xe is
>>> an rwsem, is used in a similar way as the mmap_lock. It's protecting
>>> the page-table structures and vma rb tree, the userptr structures and
>>> the extobj list. Basically it's taken early in the exec IOCTL, the
>>> VM_BIND ioctl, the compute rebind worker and the pagefault handler, so
>>> all of the above are just asserting that it is taken in the correct
>>> mode.
>>>
>>> But strictly with this scheme one could also use the vm's dma_resv for
>>> the extobj list since with drm_exec, it's locked before traversing the
>>> list.
>>>
>>> The whole point of this scheme is to rely on locks that you already are
>>> supposed to be holding for various reasons and is simple to comprehend.
>> I don't agree that we're supposed to hold the VM's resv lock anyways for
>> functions like drm_gpuvm_bo_put() or drm_gpuva_unlink(), but I'm fine using it
>> for that purpose nevertheless.
>>
>>>> In order to at least place lockdep checks, the driver would need to
>>>> supply the
>>>> corresponding lock's lockdep_map, because the GPUVM otherwise doesn't
>>>> know about
>>>> the lock.
>>> Yes, that sounds reasonable. One lockdep map per list.
>> I'd really like to avoid that, especially now that everything got simpler. We
>> should define the actual locks to take instead.
>>
>>>> Out of curiosity, what is the overhead of a spin_lock() that doesn't
>>>> need to
>>>> spin?
>>> I guess it's hard to tell exactly, but it is much lower on modern x86
>>> than what it used to be. Not sure about ARM, which is the other
>>> architecture important to us. I figure if there is little cache-line
>>> bouncing the main overhead comes from the implied barriers.
>>>
>>>>> A pretty simple way that would not add much code would be
>>>>>
>>>>> static void gpuvm_cond_spin_lock(const struct drm_gpuvm *gpuvm,
>>>>> spinlock_t
>>>>> *lock)
>>>>>
>>>>> {
>>>>>
>>>>>      if (!gpuvm->resv_protected_lists)
>>>>>          spin_lock(lock);
>>>>>
>>>>> }
>>>>>
>>>>>>> For such drivers, that would require anybody calling unlink to
>>>>>>> hold the vm's
>>>>>>> resv, though.
>>>>>> In V4 I want to go back to having a dedicated lock for the GEMs
>>>>>> gpuva list (or
>>>>>> VM_BO list to be more precise). We can't just use the dma-resv
>>>>>> lock for that
>>>>>> with VM_BO abstractions, because on destruction of a VM_BO we
>>>>>> otherwise wouldn't
>>>>>> be allowed to already hold the dma-resv lock. That's the fix I
>>>>>> was referring to
>>>>>> earlier.
>>>>> Yeah, I can see the need for a dedicated lock for the GEM's gpuva
>>>>> list, but
>>>>> holding the vm's dma-resv lock across the unlink shouldn't be a
>>>>> problem. We
>>>>> may free the object and a pointer to the vm's resv during unlink
>>>>> but we
>>>>> don't free the vm's resv.  It'd be a matter of ensuring that any
>>>>> calls to
>>>>> unlink from *within* drm_gpuvm allows it to be held.
>>>> Drivers calling unlink() from the fence signaling path can't use the
>>>> VM's
>>>> dma-resv lock.
>>> Yes, that made me a bit curious because in the current version the code
>>> required the object's dma_resv for unlink() which can't be grabbed
>>> either from the fence signaling path. So are there any drivers actually
>>> wanting to do that? If so, they will either need to resort to the
>>> current spinlock solution or they will need to call unlink from a
>>> workqueue item.
>> As Boris already mentioned we have the dma-resv lock by default or a driver
>> specific GEM gpuva lock as opt-in. Now, we can get rid of the latter.
>>
>>>> Also, what if the object is an external object? We can't use the VM's
>>>> dma-resv
>>>> lock here.
>>> Why? Typically (sync) unlink is only ever called from an unbind-like
>>> operation where it should be trivial to grab the vm's resv. Or, for
>>> that matter any outer lock protecting the extobj list. Rule would be
>>> the drm_gpuvm_bo::entry::extobj  and drm_gpuvm_bo::entry::evict would
>>> be protected by either the vm's dma_resv (or possibly an outer lock in
>>> the case of the extobj list).
>> Outer lock wouldn't have been working for updates in the async path, but
>> shouldn't be relevant anymore. We could use the VM's resv for that.
>>
>>>>   And we can't have the GEM objs dma-resv lock held when calling
>>>> unlink(), since unlink() calls drm_gpuvm_bo_put(), which if the
>>>> refcount drops
>>>> to zero calls drm_gpuvm_bo_destroy() and drm_gpuvm_bo_destroy() might
>>>> drop the
>>>> last reference of the GEM object.
>>> Yes, but this is a different problem as to what exactly protects
>>> drm_gpuvm_bo::entry::gem. Either as you suggest an internal per bo list
>>> lock, or if we want to keep the bo's dma_resv we need to ensure that
>>> the caller of dma_resv_unlock(obj->resv) actually refcounts its obj
>>> pointer, and doesn't implicitly rely on the gpuvm_bo's refcount (I know
>>> Boris didn't like that, but requiring an explicit refcount for a
>>> pointer you dereference unless you're under a lock that ensures keeping
>>> the object alive is pretty much required?) But anyway for the
>>> drm_gpuvm_bo::entry::gem list protection (bo resv or internal spinlock)
>>> I don't have a strong preference.
>> We can keep the GEM objects dma-resv lock, however as mentioned above
>> drm_gpuva_unlink() and drm_gpuvm_bo_put() then requires both the VM's resv lock
>> and the GEM's resv lock in case they differ.
>>
>>>>   All those problems go away with a dedicated
>>>> GEM gpuva list lock.
>>> I don't think these are real problems.
>>> With the excepton of the eviction list "trick" where we currently have
>>> slightly different approach to collect external bos needing rebinding,
>>> we have this working fine.
>>>
>>> TBH I think pretty much the only situation where the spinlock is needed
>>> is for async updates of these lists, unless a wq item can be used for
>>> that, but it doesn't really seem like the current code allows for such
>>> updates anyway? It complicates the code a lot, adds overhead and also
>>> adds the requirement for refcounting during list traversal.
>>>
>>> /Thomas
>>>
>>>>> /Thomas
>>>>>
>>>>>
>>>>>>> It seems that with that also the refcount could be make non-
>>>>>>> atomic.
>>>>>>>
>>>>>>> All in the spirit of the drm locking guidelines "use big locks
>>>>>>> when
>>>>>>> possible".
>>>>>>> Lower level locks only when necessary for performance or
>>>>>>> locking inversion?
>>>>>>>
>>>>>>> /Thomas
>>>>>>>
>>>>>>>
>>>>>>>> + *
>>>>>>>> + * Elements popped from the original list are kept in a
>>>>>>>> local list, so removal
>>>>>>>> + * and is_empty checks can still happen while we're
>>>>>>>> iterating the list.
>>>>>>>> + */
>>>>>>>> +#define get_next_vm_bo_from_list(__gpuvm, __list_name,
>>>>>>>> __local_list, __prev_vm_bo)     \
>>>>>>>> +       ({
>>>>>>>>                             \
>>>>>>>> +               struct drm_gpuvm_bo
>>>>>>>> *__vm_bo;                                           \
>>>>>>>> +
>>>>>>>>                             \
>>>>>>>> +               drm_gpuvm_bo_put(__prev_vm_bo);
>>>>>>>>                             \
>>>>>>>> +
>>>>>>>>                             \
>>>>>>>> +               spin_lock(&(__gpuvm)-
>>>>>>>>> __list_name.lock);                                \
>>>>>>>> +               while (!list_empty(&(__gpuvm)-
>>>>>>>>> __list_name.list)) {                     \
>>>>>>>> +                       __vm_bo =
>>>>>>>> list_first_entry(&(__gpuvm)->__list_name.list,        \
>>>>>>>> +                                                  struct
>>>>>>>> drm_gpuvm_bo,                 \
>>>>>>>> +
>>>>>>>> list.entry.__list_name);             \
>>>>>>>> +                       if
>>>>>>>> (drm_gpuvm_bo_get_unless_zero(__vm_bo))
>>>>>>>> {                    \
>>>>>>>> +                               list_move_tail(&(__vm_bo)-
>>>>>>>>> list.entry.__list_name,      \
>>>>>>>> +
>>>>>>>> __local_list);                           \
>>>>>>>> +                               break;
>>>>>>>>                             \
>>>>>>>> +                       } else
>>>>>>>> {                                                        \
>>>>>>>> +                               list_del_init(&(__vm_bo)-
>>>>>>>>> list.entry.__list_name);      \
>>>>>>>> +                               __vm_bo =
>>>>>>>> NULL;                                         \
>>>>>>>> +                       }
>>>>>>>>                             \
>>>>>>>> +               }
>>>>>>>>                             \
>>>>>>>> +               spin_unlock(&(__gpuvm)-
>>>>>>>>> __list_name.lock);                              \
>>>>>>>> +
>>>>>>>>                             \
>>>>>>>> +               __vm_bo;
>>>>>>>>                             \
>>>>>>>> +       })
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * for_each_vm_bo_in_list() - internal vm_bo list iterator
>>>>>>>> + *
>>>>>>>> + * This helper is here to provide lockless list iteration.
>>>>>>>> Lockless as in, the
>>>>>>>> + * iterator releases the lock immediately after picking the
>>>>>>>> first element from the
>>>>>>>> + * list, so list insertion and deletion can happen
>>>>>>>> concurrently.
>>>>>>>> + *
>>>>>>>> + * Typical use:
>>>>>>>> + *
>>>>>>>> + *     struct drm_gpuvm_bo *vm_bo;
>>>>>>>> + *     LIST_HEAD(my_local_list);
>>>>>>>> + *
>>>>>>>> + *     ret = 0;
>>>>>>>> + *     drm_gpuvm_for_each_vm_bo(gpuvm, <list_name>,
>>>>>>>> &my_local_list, vm_bo) {
>>>>>>>> + *             ret = do_something_with_vm_bo(..., vm_bo);
>>>>>>>> + *             if (ret)
>>>>>>>> + *                     break;
>>>>>>>> + *     }
>>>>>>>> + *     drm_gpuvm_bo_put(vm_bo);
>>>>>>>> + *     drm_gpuvm_restore_vm_bo_list(gpuvm, <list_name>,
>>>>>>>> &my_local_list);
>>>>>>>> + *
>>>>>>>> + *
>>>>>>>> + * Only used for internal list iterations, not meant to be
>>>>>>>> exposed to the outside
>>>>>>>> + * world.
>>>>>>>> + */
>>>>>>>> +#define for_each_vm_bo_in_list(__gpuvm, __list_name,
>>>>>>>> __local_list, __vm_bo)    \
>>>>>>>> +       for (__vm_bo = get_next_vm_bo_from_list(__gpuvm,
>>>>>>>> __list_name,           \
>>>>>>>> +                                               __local_list,
>>>>>>>> NULL);            \
>>>>>>>> +
>>>>>>>> __vm_bo;
>>>>>>>>        \
>>>>>>>> +            __vm_bo = get_next_vm_bo_from_list(__gpuvm,
>>>>>>>> __list_name,           \
>>>>>>>> +                                               __local_list,
>>>>>>>> __vm_bo))         \
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * restore_vm_bo_list() - move vm_bo elements back to their
>>>>>>>> original list
>>>>>>>> + * @__gpuvm: The GPU VM
>>>>>>>> + * @__list_name: The name of the list we're iterating on
>>>>>>>> + * @__local_list: A pointer to the local list used to store
>>>>>>>> already iterated items
>>>>>>>> + *
>>>>>>>> + * When we're done iterating a vm_bo list, we should call
>>>>>>>> restore_vm_bo_list()
>>>>>>>> + * to restore the original state and let new iterations take
>>>>>>>> place.
>>>>>>>> + */
>>>>>>>> +#define restore_vm_bo_list(__gpuvm, __list_name,
>>>>>>>> __local_list)                         \
>>>>>>>> +       do
>>>>>>>> {
>>>>>>>>                  \
>>>>>>>> +               /* Merge back the two lists, moving local
>>>>>>>> list elements to the          \
>>>>>>>> +                * head to preserve previous ordering, in
>>>>>>>> case it matters.              \
>>>>>>>> +
>>>>>>>> */
>>>>>>>>            \
>>>>>>>> +               spin_lock(&(__gpuvm)-
>>>>>>>>> __list_name.lock);                                \
>>>>>>>> +               list_splice(__local_list, &(__gpuvm)-
>>>>>>>>> __list_name.list);                \
>>>>>>>> +               spin_unlock(&(__gpuvm)-
>>>>>>>>> __list_name.lock);                              \
>>>>>>>> +       } while (0)
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_bo_list_add() - insert a vm_bo into the given
>>>>>>>> list
>>>>>>>> + * @__vm_bo: the &drm_gpuvm_bo
>>>>>>>> + * @__list_name: the name of the list to insert into
>>>>>>>> + *
>>>>>>>> + * Inserts the given @__vm_bo into the list specified by
>>>>>>>> @__list_name and
>>>>>>>> + * increases the vm_bo's reference count.
>>>>>>>> + */
>>>>>>>> +#define drm_gpuvm_bo_list_add(__vm_bo,
>>>>>>>> __list_name)                            \
>>>>>>>> +       do
>>>>>>>> {
>>>>>>>>          \
>>>>>>>> +               spin_lock(&(__vm_bo)->vm-
>>>>>>>>> __list_name.lock);                    \
>>>>>>>> +               if (list_empty(&(__vm_bo)-
>>>>>>>>> list.entry.__list_name))             \
>>>>>>>> +                       list_add_tail(&(__vm_bo)-
>>>>>>>>> list.entry.__list_name,       \
>>>>>>>> +                                     &(__vm_bo)->vm-
>>>>>>>>> __list_name.list);        \
>>>>>>>> +               spin_unlock(&(__vm_bo)->vm-
>>>>>>>>> __list_name.lock);                  \
>>>>>>>> +       } while (0)
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_bo_list_del() - remove a vm_bo from the given
>>>>>>>> list
>>>>>>>> + * @__vm_bo: the &drm_gpuvm_bo
>>>>>>>> + * @__list_name: the name of the list to insert into
>>>>>>>> + *
>>>>>>>> + * Removes the given @__vm_bo from the list specified by
>>>>>>>> @__list_name and
>>>>>>>> + * decreases the vm_bo's reference count.
>>>>>>>> + */
>>>>>>>> +#define drm_gpuvm_bo_list_del(__vm_bo,
>>>>>>>> __list_name)                            \
>>>>>>>> +       do
>>>>>>>> {
>>>>>>>>          \
>>>>>>>> +               spin_lock(&(__vm_bo)->vm-
>>>>>>>>> __list_name.lock);                    \
>>>>>>>> +               if (!list_empty(&(__vm_bo)-
>>>>>>>>> list.entry.__list_name))            \
>>>>>>>> +                       list_del_init(&(__vm_bo)-
>>>>>>>>> list.entry.__list_name);      \
>>>>>>>> +               spin_unlock(&(__vm_bo)->vm-
>>>>>>>>> __list_name.lock);                  \
>>>>>>>> +       } while (0)
>>>>>>>> +
>>>>>>>> +static int __must_check
>>>>>>>> +drm_gpuvm_bo_get_unless_zero(struct drm_gpuvm_bo *vm_bo);
>>>>>>>> +
>>>>>>>>     #define to_drm_gpuva(__node) container_of((__node), struct
>>>>>>>> drm_gpuva, rb.node)
>>>>>>>>     #define GPUVA_START(node) ((node)->va.addr)
>>>>>>>> @@ -713,6 +867,12 @@ drm_gpuvm_init(struct drm_gpuvm *gpuvm,
>>>>>>>> struct drm_device *drm,
>>>>>>>>          gpuvm->rb.tree = RB_ROOT_CACHED;
>>>>>>>>          INIT_LIST_HEAD(&gpuvm->rb.list);
>>>>>>>> +       INIT_LIST_HEAD(&gpuvm->extobj.list);
>>>>>>>> +       spin_lock_init(&gpuvm->extobj.lock);
>>>>>>>> +
>>>>>>>> +       INIT_LIST_HEAD(&gpuvm->evict.list);
>>>>>>>> +       spin_lock_init(&gpuvm->evict.lock);
>>>>>>>> +
>>>>>>>>          drm_gpuva_check_overflow(start_offset, range);
>>>>>>>>          gpuvm->mm_start = start_offset;
>>>>>>>>          gpuvm->mm_range = range;
>>>>>>>> @@ -754,10 +914,302 @@ drm_gpuvm_destroy(struct drm_gpuvm
>>>>>>>> *gpuvm)
>>>>>>>>          WARN(!RB_EMPTY_ROOT(&gpuvm->rb.tree.rb_root),
>>>>>>>>               "GPUVA tree is not empty, potentially leaking
>>>>>>>> memory.\n");
>>>>>>>> +       WARN(!list_empty(&gpuvm->extobj.list), "Extobj list
>>>>>>>> should be empty.\n");
>>>>>>>> +       WARN(!list_empty(&gpuvm->evict.list), "Evict list
>>>>>>>> should be empty.\n");
>>>>>>>> +
>>>>>>>>          drm_gem_private_object_fini(&gpuvm->d_obj);
>>>>>>>>     }
>>>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_prepare_objects() - prepare all assoiciated BOs
>>>>>>>> + * @gpuvm: the &drm_gpuvm
>>>>>>>> + * @exec: the &drm_exec locking context
>>>>>>>> + * @num_fences: the amount of &dma_fences to reserve
>>>>>>>> + *
>>>>>>>> + * Calls drm_exec_prepare_obj() for all &drm_gem_objects the
>>>>>>>> given
>>>>>>>> + * &drm_gpuvm contains mappings of.
>>>>>>>> + *
>>>>>>>> + * Using this function directly, it is the drivers
>>>>>>>> responsibility to call
>>>>>>>> + * drm_exec_init() and drm_exec_fini() accordingly.
>>>>>>>> + *
>>>>>>>> + * Note: This function is safe against concurrent insertion
>>>>>>>> and removal of
>>>>>>>> + * external objects, however it is not safe against
>>>>>>>> concurrent usage itself.
>>>>>>>> + *
>>>>>>>> + * Drivers need to make sure to protect this case with
>>>>>>>> either an outer VM lock
>>>>>>>> + * or by calling drm_gpuvm_prepare_vm() before this function
>>>>>>>> within the
>>>>>>>> + * drm_exec_until_all_locked() loop, such that the GPUVM's
>>>>>>>> dma-resv lock ensures
>>>>>>>> + * mutual exclusion.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +int
>>>>>>>> +drm_gpuvm_prepare_objects(struct drm_gpuvm *gpuvm,
>>>>>>>> +                         struct drm_exec *exec,
>>>>>>>> +                         unsigned int num_fences)
>>>>>>>> +{
>>>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>>>> +       LIST_HEAD(extobjs);
>>>>>>>> +       int ret = 0;
>>>>>>>> +
>>>>>>>> +       for_each_vm_bo_in_list(gpuvm, extobj, &extobjs,
>>>>>>>> vm_bo) {
>>>>>>>> +               ret = drm_exec_prepare_obj(exec, vm_bo->obj,
>>>>>>>> num_fences);
>>>>>>>> +               if (ret)
>>>>>>>> +                       break;
>>>>>>>> +       }
>>>>>>>> +       /* Drop ref in case we break out of the loop. */
>>>>>>>> +       drm_gpuvm_bo_put(vm_bo);
>>>>>>>> +       restore_vm_bo_list(gpuvm, extobj, &extobjs);
>>>>>>>> +
>>>>>>>> +       return ret;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_prepare_objects);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_prepare_range() - prepare all BOs mapped within
>>>>>>>> a given range
>>>>>>>> + * @gpuvm: the &drm_gpuvm
>>>>>>>> + * @exec: the &drm_exec locking context
>>>>>>>> + * @addr: the start address within the VA space
>>>>>>>> + * @range: the range to iterate within the VA space
>>>>>>>> + * @num_fences: the amount of &dma_fences to reserve
>>>>>>>> + *
>>>>>>>> + * Calls drm_exec_prepare_obj() for all &drm_gem_objects
>>>>>>>> mapped between @addr
>>>>>>>> + * and @addr + @range.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +int
>>>>>>>> +drm_gpuvm_prepare_range(struct drm_gpuvm *gpuvm, struct
>>>>>>>> drm_exec *exec,
>>>>>>>> +                       u64 addr, u64 range, unsigned int
>>>>>>>> num_fences)
>>>>>>>> +{
>>>>>>>> +       struct drm_gpuva *va;
>>>>>>>> +       u64 end = addr + range;
>>>>>>>> +       int ret;
>>>>>>>> +
>>>>>>>> +       drm_gpuvm_for_each_va_range(va, gpuvm, addr, end) {
>>>>>>>> +               struct drm_gem_object *obj = va->gem.obj;
>>>>>>>> +
>>>>>>>> +               ret = drm_exec_prepare_obj(exec, obj,
>>>>>>>> num_fences);
>>>>>>>> +               if (ret)
>>>>>>>> +                       return ret;
>>>>>>>> +       }
>>>>>>>> +
>>>>>>>> +       return 0;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_prepare_range);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_exec_lock() - lock all dma-resv of all
>>>>>>>> assoiciated BOs
>>>>>>>> + * @vm_exec: the &drm_gpuvm_exec abstraction
>>>>>>>> + * @num_fences: the amount of &dma_fences to reserve
>>>>>>>> + * @interruptible: sleep interruptible if waiting
>>>>>>>> + *
>>>>>>>> + * Acquires all dma-resv locks of all &drm_gem_objects the
>>>>>>>> given
>>>>>>>> + * &drm_gpuvm contains mappings of.
>>>>>>>> + *
>>>>>>>> + * Addionally, when calling this function with struct
>>>>>>>> drm_gpuvm_exec::extra
>>>>>>>> + * being set the driver receives the given @fn callback to
>>>>>>>> lock additional
>>>>>>>> + * dma-resv in the context of the &drm_gpuvm_exec instance.
>>>>>>>> Typically, drivers
>>>>>>>> + * would call drm_exec_prepare_obj() from within this
>>>>>>>> callback.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +int
>>>>>>>> +drm_gpuvm_exec_lock(struct drm_gpuvm_exec *vm_exec,
>>>>>>>> +                   unsigned int num_fences,
>>>>>>>> +                   bool interruptible)
>>>>>>>> +{
>>>>>>>> +       struct drm_gpuvm *gpuvm = vm_exec->vm;
>>>>>>>> +       struct drm_exec *exec = &vm_exec->exec;
>>>>>>>> +       uint32_t flags;
>>>>>>>> +       int ret;
>>>>>>>> +
>>>>>>>> +       flags = interruptible ? DRM_EXEC_INTERRUPTIBLE_WAIT :
>>>>>>>> 0 |
>>>>>>>> +               DRM_EXEC_IGNORE_DUPLICATES;
>>>>>>>> +
>>>>>>>> +       drm_exec_init(exec, flags);
>>>>>>>> +
>>>>>>>> +       drm_exec_until_all_locked(exec) {
>>>>>>>> +               ret = drm_gpuvm_prepare_vm(gpuvm, exec,
>>>>>>>> num_fences);
>>>>>>>> +               drm_exec_retry_on_contention(exec);
>>>>>>>> +               if (ret)
>>>>>>>> +                       goto err;
>>>>>>>> +
>>>>>>>> +               ret = drm_gpuvm_prepare_objects(gpuvm, exec,
>>>>>>>> num_fences);
>>>>>>>> +               drm_exec_retry_on_contention(exec);
>>>>>>>> +               if (ret)
>>>>>>>> +                       goto err;
>>>>>>>> +
>>>>>>>> +               if (vm_exec->extra.fn) {
>>>>>>>> +                       ret = vm_exec->extra.fn(vm_exec,
>>>>>>>> num_fences);
>>>>>>>> +                       drm_exec_retry_on_contention(exec);
>>>>>>>> +                       if (ret)
>>>>>>>> +                               goto err;
>>>>>>>> +               }
>>>>>>>> +       }
>>>>>>>> +
>>>>>>>> +       return 0;
>>>>>>>> +
>>>>>>>> +err:
>>>>>>>> +       drm_exec_fini(exec);
>>>>>>>> +       return ret;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_exec_lock);
>>>>>>>> +
>>>>>>>> +static int
>>>>>>>> +fn_lock_array(struct drm_gpuvm_exec *vm_exec, unsigned int
>>>>>>>> num_fences)
>>>>>>>> +{
>>>>>>>> +       struct {
>>>>>>>> +               struct drm_gem_object **objs;
>>>>>>>> +               unsigned int num_objs;
>>>>>>>> +       } *args = vm_exec->extra.priv;
>>>>>>>> +
>>>>>>>> +       return drm_exec_prepare_array(&vm_exec->exec, args-
>>>>>>>>> objs,
>>>>>>>> +                                     args->num_objs,
>>>>>>>> num_fences);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_exec_lock_array() - lock all dma-resv of all
>>>>>>>> assoiciated BOs
>>>>>>>> + * @vm_exec: the &drm_gpuvm_exec abstraction
>>>>>>>> + * @objs: additional &drm_gem_objects to lock
>>>>>>>> + * @num_objs: the number of additional &drm_gem_objects to
>>>>>>>> lock
>>>>>>>> + * @num_fences: the amount of &dma_fences to reserve
>>>>>>>> + * @interruptible: sleep interruptible if waiting
>>>>>>>> + *
>>>>>>>> + * Acquires all dma-resv locks of all &drm_gem_objects the
>>>>>>>> given &drm_gpuvm
>>>>>>>> + * contains mappings of, plus the ones given through @objs.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +int
>>>>>>>> +drm_gpuvm_exec_lock_array(struct drm_gpuvm_exec *vm_exec,
>>>>>>>> +                         struct drm_gem_object **objs,
>>>>>>>> +                         unsigned int num_objs,
>>>>>>>> +                         unsigned int num_fences,
>>>>>>>> +                         bool interruptible)
>>>>>>>> +{
>>>>>>>> +       struct {
>>>>>>>> +               struct drm_gem_object **objs;
>>>>>>>> +               unsigned int num_objs;
>>>>>>>> +       } args;
>>>>>>>> +
>>>>>>>> +       args.objs = objs;
>>>>>>>> +       args.num_objs = num_objs;
>>>>>>>> +
>>>>>>>> +       vm_exec->extra.fn = fn_lock_array;
>>>>>>>> +       vm_exec->extra.priv = &args;
>>>>>>>> +
>>>>>>>> +       return drm_gpuvm_exec_lock(vm_exec, num_fences,
>>>>>>>> interruptible);
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_exec_lock_array);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_exec_lock_range() - prepare all BOs mapped
>>>>>>>> within a given range
>>>>>>>> + * @vm_exec: the &drm_gpuvm_exec abstraction
>>>>>>>> + * @addr: the start address within the VA space
>>>>>>>> + * @range: the range to iterate within the VA space
>>>>>>>> + * @num_fences: the amount of &dma_fences to reserve
>>>>>>>> + * @interruptible: sleep interruptible if waiting
>>>>>>>> + *
>>>>>>>> + * Acquires all dma-resv locks of all &drm_gem_objects
>>>>>>>> mapped between @addr and
>>>>>>>> + * @addr + @range.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +int
>>>>>>>> +drm_gpuvm_exec_lock_range(struct drm_gpuvm_exec *vm_exec,
>>>>>>>> +                         u64 addr, u64 range,
>>>>>>>> +                         unsigned int num_fences,
>>>>>>>> +                         bool interruptible)
>>>>>>>> +{
>>>>>>>> +       struct drm_gpuvm *gpuvm = vm_exec->vm;
>>>>>>>> +       struct drm_exec *exec = &vm_exec->exec;
>>>>>>>> +       uint32_t flags;
>>>>>>>> +       int ret;
>>>>>>>> +
>>>>>>>> +       flags = interruptible ? DRM_EXEC_INTERRUPTIBLE_WAIT :
>>>>>>>> 0 |
>>>>>>>> +               DRM_EXEC_IGNORE_DUPLICATES;
>>>>>>>> +
>>>>>>>> +       drm_exec_init(exec, flags);
>>>>>>>> +
>>>>>>>> +       drm_exec_until_all_locked(exec) {
>>>>>>>> +               ret = drm_gpuvm_prepare_range(gpuvm, exec,
>>>>>>>> addr, range,
>>>>>>>> +                                             num_fences);
>>>>>>>> +               drm_exec_retry_on_contention(exec);
>>>>>>>> +               if (ret)
>>>>>>>> +                       goto err;
>>>>>>>> +       }
>>>>>>>> +
>>>>>>>> +       return ret;
>>>>>>>> +
>>>>>>>> +err:
>>>>>>>> +       drm_exec_fini(exec);
>>>>>>>> +       return ret;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_exec_lock_range);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_validate() - validate all BOs marked as evicted
>>>>>>>> + * @gpuvm: the &drm_gpuvm to validate evicted BOs
>>>>>>>> + *
>>>>>>>> + * Calls the &drm_gpuvm_ops.bo_validate callback for all
>>>>>>>> evicted buffer
>>>>>>>> + * objects being mapped in the given &drm_gpuvm.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +int
>>>>>>>> +drm_gpuvm_validate(struct drm_gpuvm *gpuvm)
>>>>>>>> +{
>>>>>>>> +       const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>>>> +       LIST_HEAD(evict);
>>>>>>>> +       int ret = 0;
>>>>>>>> +
>>>>>>>> +       if (unlikely(!ops || !ops->bo_validate))
>>>>>>>> +               return -ENOTSUPP;
>>>>>>>> +
>>>>>>>> +       for_each_vm_bo_in_list(gpuvm, evict, &evict, vm_bo) {
>>>>>>>> +               dma_resv_assert_held(vm_bo->obj->resv);
>>>>>>>> +               ret = ops->bo_validate(vm_bo->obj);
>>>>>>>> +               if (ret)
>>>>>>>> +                       break;
>>>>>>>> +       }
>>>>>>>> +       /* Drop ref in case we break out of the loop. */
>>>>>>>> +       drm_gpuvm_bo_put(vm_bo);
>>>>>>>> +       restore_vm_bo_list(gpuvm, evict, &evict);
>>>>>>>> +
>>>>>>>> +       return ret;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_validate);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_resv_add_fence - add fence to private and all
>>>>>>>> extobj
>>>>>>>> + * dma-resv
>>>>>>>> + * @gpuvm: the &drm_gpuvm to add a fence to
>>>>>>>> + * @exec: the &drm_exec locking context
>>>>>>>> + * @fence: fence to add
>>>>>>>> + * @private_usage: private dma-resv usage
>>>>>>>> + * @extobj_usage: extobj dma-resv usage
>>>>>>>> + */
>>>>>>>> +void
>>>>>>>> +drm_gpuvm_resv_add_fence(struct drm_gpuvm *gpuvm,
>>>>>>>> +                        struct drm_exec *exec,
>>>>>>>> +                        struct dma_fence *fence,
>>>>>>>> +                        enum dma_resv_usage private_usage,
>>>>>>>> +                        enum dma_resv_usage extobj_usage)
>>>>>>>> +{
>>>>>>>> +       struct drm_gem_object *obj;
>>>>>>>> +       unsigned long index;
>>>>>>>> +
>>>>>>>> +       drm_exec_for_each_locked_object(exec, index, obj) {
>>>>>>>> +               dma_resv_assert_held(obj->resv);
>>>>>>>> +               dma_resv_add_fence(obj->resv, fence,
>>>>>>>> +                                  drm_gpuvm_is_extobj(gpuvm,
>>>>>>>> obj) ?
>>>>>>>> +                                  private_usage :
>>>>>>>> extobj_usage);
>>>>>>>> +       }
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_resv_add_fence);
>>>>>>>> +
>>>>>>>>     /**
>>>>>>>>      * drm_gpuvm_bo_create() - create a new instance of struct
>>>>>>>> drm_gpuvm_bo
>>>>>>>>      * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>>>>>>> @@ -790,6 +1242,9 @@ drm_gpuvm_bo_create(struct drm_gpuvm
>>>>>>>> *gpuvm,
>>>>>>>>          INIT_LIST_HEAD(&vm_bo->list.gpuva);
>>>>>>>>          INIT_LIST_HEAD(&vm_bo->list.entry.gem);
>>>>>>>> +       INIT_LIST_HEAD(&vm_bo->list.entry.extobj);
>>>>>>>> +       INIT_LIST_HEAD(&vm_bo->list.entry.evict);
>>>>>>>> +
>>>>>>>>          drm_gem_object_get(obj);
>>>>>>>>          return vm_bo;
>>>>>>>> @@ -807,6 +1262,14 @@ drm_gpuvm_bo_destroy(struct kref *kref)
>>>>>>>>          drm_gem_gpuva_assert_lock_held(vm_bo->obj);
>>>>>>>> +       spin_lock(&gpuvm->extobj.lock);
>>>>>>>> +       list_del(&vm_bo->list.entry.extobj);
>>>>>>>> +       spin_unlock(&gpuvm->extobj.lock);
>>>>>>>> +
>>>>>>>> +       spin_lock(&gpuvm->evict.lock);
>>>>>>>> +       list_del(&vm_bo->list.entry.evict);
>>>>>>>> +       spin_unlock(&gpuvm->evict.lock);
>>>>>>>> +
>>>>>>>>          list_del(&vm_bo->list.entry.gem);
>>>>>>>>          drm_gem_object_put(obj);
>>>>>>>> @@ -822,6 +1285,11 @@ drm_gpuvm_bo_destroy(struct kref *kref)
>>>>>>>>      * @vm_bo: the &drm_gpuvm_bo to release the reference of
>>>>>>>>      *
>>>>>>>>      * This releases a reference to @vm_bo.
>>>>>>>> + *
>>>>>>>> + * If the reference count drops to zero, the &gpuvm_bo is
>>>>>>>> destroyed, which
>>>>>>>> + * includes removing it from the GEMs gpuva list. Hence, if
>>>>>>>> a call to this
>>>>>>>> + * function can potentially let the reference count to zero
>>>>>>>> the caller must
>>>>>>>> + * hold the dma-resv or driver specific GEM gpuva lock.
>>>>>>>>      */
>>>>>>>>     void
>>>>>>>>     drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
>>>>>>>> @@ -831,6 +1299,12 @@ drm_gpuvm_bo_put(struct drm_gpuvm_bo
>>>>>>>> *vm_bo)
>>>>>>>>     }
>>>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
>>>>>>>> +static int __must_check
>>>>>>>> +drm_gpuvm_bo_get_unless_zero(struct drm_gpuvm_bo *vm_bo)
>>>>>>>> +{
>>>>>>>> +       return kref_get_unless_zero(&vm_bo->kref);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>     static struct drm_gpuvm_bo *
>>>>>>>>     __drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>>>>>>>                      struct drm_gem_object *obj)
>>>>>>>> @@ -938,6 +1412,48 @@ drm_gpuvm_bo_obtain_prealloc(struct
>>>>>>>> drm_gpuvm_bo *__vm_bo)
>>>>>>>>     }
>>>>>>>>     EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_bo_extobj_add() - adds the &drm_gpuvm_bo to its
>>>>>>>> &drm_gpuvm's
>>>>>>>> + * extobj list
>>>>>>>> + * @vm_bo: The &drm_gpuvm_bo to add to its &drm_gpuvm's the
>>>>>>>> extobj list.
>>>>>>>> + *
>>>>>>>> + * Adds the given @vm_bo to its &drm_gpuvm's extobj list if
>>>>>>>> not on the list
>>>>>>>> + * already and if the corresponding &drm_gem_object is an
>>>>>>>> external object,
>>>>>>>> + * actually.
>>>>>>>> + */
>>>>>>>> +void
>>>>>>>> +drm_gpuvm_bo_extobj_add(struct drm_gpuvm_bo *vm_bo)
>>>>>>>> +{
>>>>>>>> +       struct drm_gpuvm *gpuvm = vm_bo->vm;
>>>>>>>> +
>>>>>>>> +       if (drm_gpuvm_is_extobj(gpuvm, vm_bo->obj))
>>>>>>>> +               drm_gpuvm_bo_list_add(vm_bo, extobj);
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_extobj_add);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_bo_evict() - add / remove a &drm_gem_object to
>>>>>>>> / from a
>>>>>>>> + * &drm_gpuvms evicted list
>>>>>>>> + * @obj: the &drm_gem_object to add or remove
>>>>>>>> + * @evict: indicates whether the object is evicted
>>>>>>>> + *
>>>>>>>> + * Adds a &drm_gem_object to or removes it from all
>>>>>>>> &drm_gpuvms evicted
>>>>>>>> + * list containing a mapping of this &drm_gem_object.
>>>>>>>> + */
>>>>>>>> +void
>>>>>>>> +drm_gpuvm_bo_evict(struct drm_gem_object *obj, bool evict)
>>>>>>>> +{
>>>>>>>> +       struct drm_gpuvm_bo *vm_bo;
>>>>>>>> +
>>>>>>>> +       drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>>>>>>> +               if (evict)
>>>>>>>> +                       drm_gpuvm_bo_list_add(vm_bo, evict);
>>>>>>>> +               else
>>>>>>>> +                       drm_gpuvm_bo_list_del(vm_bo, evict);
>>>>>>>> +       }
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_evict);
>>>>>>>> +
>>>>>>>>     static int
>>>>>>>>     __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
>>>>>>>>                     struct drm_gpuva *va)
>>>>>>>> diff --git a/include/drm/drm_gpuvm.h
>>>>>>>> b/include/drm/drm_gpuvm.h
>>>>>>>> index afa50b9059a2..834bb6d6617e 100644
>>>>>>>> --- a/include/drm/drm_gpuvm.h
>>>>>>>> +++ b/include/drm/drm_gpuvm.h
>>>>>>>> @@ -26,10 +26,12 @@
>>>>>>>>      */
>>>>>>>>     #include <linux/list.h>
>>>>>>>> +#include <linux/dma-resv.h>
>>>>>>>>     #include <linux/rbtree.h>
>>>>>>>>     #include <linux/types.h>
>>>>>>>>     #include <drm/drm_gem.h>
>>>>>>>> +#include <drm/drm_exec.h>
>>>>>>>>     struct drm_gpuvm;
>>>>>>>>     struct drm_gpuvm_bo;
>>>>>>>> @@ -259,6 +261,38 @@ struct drm_gpuvm {
>>>>>>>>           * space
>>>>>>>>           */
>>>>>>>>          struct dma_resv *resv;
>>>>>>>> +
>>>>>>>> +       /**
>>>>>>>> +        * @extobj: structure holding the extobj list
>>>>>>>> +        */
>>>>>>>> +       struct {
>>>>>>>> +               /**
>>>>>>>> +                * @list: &list_head storing &drm_gpuvm_bos
>>>>>>>> serving as
>>>>>>>> +                * external object
>>>>>>>> +                */
>>>>>>>> +               struct list_head list;
>>>>>>>> +
>>>>>>>> +               /**
>>>>>>>> +                * @lock: spinlock to protect the extobj list
>>>>>>>> +                */
>>>>>>>> +               spinlock_t lock;
>>>>>>>> +       } extobj;
>>>>>>>> +
>>>>>>>> +       /**
>>>>>>>> +        * @evict: structure holding the evict list and evict
>>>>>>>> list lock
>>>>>>>> +        */
>>>>>>>> +       struct {
>>>>>>>> +               /**
>>>>>>>> +                * @list: &list_head storing &drm_gpuvm_bos
>>>>>>>> currently being
>>>>>>>> +                * evicted
>>>>>>>> +                */
>>>>>>>> +               struct list_head list;
>>>>>>>> +
>>>>>>>> +               /**
>>>>>>>> +                * @lock: spinlock to protect the evict list
>>>>>>>> +                */
>>>>>>>> +               spinlock_t lock;
>>>>>>>> +       } evict;
>>>>>>>>     };
>>>>>>>>     void drm_gpuvm_init(struct drm_gpuvm *gpuvm, struct
>>>>>>>> drm_device *drm,
>>>>>>>> @@ -268,6 +302,21 @@ void drm_gpuvm_init(struct drm_gpuvm
>>>>>>>> *gpuvm, struct drm_device *drm,
>>>>>>>>                      const struct drm_gpuvm_ops *ops);
>>>>>>>>     void drm_gpuvm_destroy(struct drm_gpuvm *gpuvm);
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_is_extobj() - indicates whether the given
>>>>>>>> &drm_gem_object is an
>>>>>>>> + * external object
>>>>>>>> + * @gpuvm: the &drm_gpuvm to check
>>>>>>>> + * @obj: the &drm_gem_object to check
>>>>>>>> + *
>>>>>>>> + * Returns: true if the &drm_gem_object &dma_resv differs
>>>>>>>> from the
>>>>>>>> + * &drm_gpuvms &dma_resv, false otherwise
>>>>>>>> + */
>>>>>>>> +static inline bool drm_gpuvm_is_extobj(struct drm_gpuvm
>>>>>>>> *gpuvm,
>>>>>>>> +                                      struct drm_gem_object
>>>>>>>> *obj)
>>>>>>>> +{
>>>>>>>> +       return obj && obj->resv != gpuvm->resv;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>     static inline struct drm_gpuva *
>>>>>>>>     __drm_gpuva_next(struct drm_gpuva *va)
>>>>>>>>     {
>>>>>>>> @@ -346,6 +395,128 @@ __drm_gpuva_next(struct drm_gpuva *va)
>>>>>>>>     #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__)
>>>>>>>> \
>>>>>>>>          list_for_each_entry_safe(va__, next__, &(gpuvm__)-
>>>>>>>>> rb.list, rb.entry)
>>>>>>>> +/**
>>>>>>>> + * struct drm_gpuvm_exec - &drm_gpuvm abstraction of
>>>>>>>> &drm_exec
>>>>>>>> + *
>>>>>>>> + * This structure should be created on the stack as
>>>>>>>> &drm_exec should be.
>>>>>>>> + *
>>>>>>>> + * Optionally, @extra can be set in order to lock additional
>>>>>>>> &drm_gem_objects.
>>>>>>>> + */
>>>>>>>> +struct drm_gpuvm_exec {
>>>>>>>> +       /**
>>>>>>>> +        * @exec: the &drm_exec structure
>>>>>>>> +        */
>>>>>>>> +       struct drm_exec exec;
>>>>>>>> +
>>>>>>>> +       /**
>>>>>>>> +        * @vm: the &drm_gpuvm to lock its DMA reservations
>>>>>>>> +        */
>>>>>>>> +       struct drm_gpuvm *vm;
>>>>>>>> +
>>>>>>>> +       /**
>>>>>>>> +        * @extra: Callback and corresponding private data
>>>>>>>> for the driver to
>>>>>>>> +        * lock arbitrary additional &drm_gem_objects.
>>>>>>>> +        */
>>>>>>>> +       struct {
>>>>>>>> +               /**
>>>>>>>> +                * @fn: The driver callback to lock
>>>>>>>> additional &drm_gem_objects.
>>>>>>>> +                */
>>>>>>>> +               int (*fn)(struct drm_gpuvm_exec *vm_exec,
>>>>>>>> +                         unsigned int num_fences);
>>>>>>>> +
>>>>>>>> +               /**
>>>>>>>> +                * @priv: driver private data for the @fn
>>>>>>>> callback
>>>>>>>> +                */
>>>>>>>> +               void *priv;
>>>>>>>> +       } extra;
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_prepare_vm() - prepare the GPUVMs common dma-
>>>>>>>> resv
>>>>>>>> + * @gpuvm: the &drm_gpuvm
>>>>>>>> + * @exec: the &drm_exec context
>>>>>>>> + * @num_fences: the amount of &dma_fences to reserve
>>>>>>>> + *
>>>>>>>> + * Calls drm_exec_prepare_obj() for the GPUVMs dummy
>>>>>>>> &drm_gem_object.
>>>>>>>> + *
>>>>>>>> + * Using this function directly, it is the drivers
>>>>>>>> responsibility to call
>>>>>>>> + * drm_exec_init() and drm_exec_fini() accordingly.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +static inline int
>>>>>>>> +drm_gpuvm_prepare_vm(struct drm_gpuvm *gpuvm,
>>>>>>>> +                    struct drm_exec *exec,
>>>>>>>> +                    unsigned int num_fences)
>>>>>>>> +{
>>>>>>>> +       return drm_exec_prepare_obj(exec, &gpuvm->d_obj,
>>>>>>>> num_fences);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +int drm_gpuvm_prepare_objects(struct drm_gpuvm *gpuvm,
>>>>>>>> +                             struct drm_exec *exec,
>>>>>>>> +                             unsigned int num_fences);
>>>>>>>> +
>>>>>>>> +int drm_gpuvm_prepare_range(struct drm_gpuvm *gpuvm,
>>>>>>>> +                           struct drm_exec *exec,
>>>>>>>> +                           u64 addr, u64 range,
>>>>>>>> +                           unsigned int num_fences);
>>>>>>>> +
>>>>>>>> +int drm_gpuvm_exec_lock(struct drm_gpuvm_exec *vm_exec,
>>>>>>>> +                       unsigned int num_fences,
>>>>>>>> +                       bool interruptible);
>>>>>>>> +
>>>>>>>> +int drm_gpuvm_exec_lock_array(struct drm_gpuvm_exec
>>>>>>>> *vm_exec,
>>>>>>>> +                             struct drm_gem_object **objs,
>>>>>>>> +                             unsigned int num_objs,
>>>>>>>> +                             unsigned int num_fences,
>>>>>>>> +                             bool interruptible);
>>>>>>>> +
>>>>>>>> +int drm_gpuvm_exec_lock_range(struct drm_gpuvm_exec
>>>>>>>> *vm_exec,
>>>>>>>> +                             u64 addr, u64 range,
>>>>>>>> +                             unsigned int num_fences,
>>>>>>>> +                             bool interruptible);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_lock() - lock all dma-resv of all assoiciated
>>>>>>>> BOs
>>>>>>>> + * @gpuvm: the &drm_gpuvm
>>>>>>>> + *
>>>>>>>> + * Releases all dma-resv locks of all &drm_gem_objects
>>>>>>>> previously acquired
>>>>>>>> + * through drm_gpuvm_lock() or its variants.
>>>>>>>> + *
>>>>>>>> + * Returns: 0 on success, negative error code on failure.
>>>>>>>> + */
>>>>>>>> +static inline void
>>>>>>>> +drm_gpuvm_exec_unlock(struct drm_gpuvm_exec *vm_exec)
>>>>>>>> +{
>>>>>>>> +       drm_exec_fini(&vm_exec->exec);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +int drm_gpuvm_validate(struct drm_gpuvm *gpuvm);
>>>>>>>> +void drm_gpuvm_resv_add_fence(struct drm_gpuvm *gpuvm,
>>>>>>>> +                             struct drm_exec *exec,
>>>>>>>> +                             struct dma_fence *fence,
>>>>>>>> +                             enum dma_resv_usage
>>>>>>>> private_usage,
>>>>>>>> +                             enum dma_resv_usage
>>>>>>>> extobj_usage);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_gpuvm_exec_resv_add_fence()
>>>>>>>> + * @vm_exec: the &drm_gpuvm_exec abstraction
>>>>>>>> + * @fence: fence to add
>>>>>>>> + * @private_usage: private dma-resv usage
>>>>>>>> + * @extobj_usage: extobj dma-resv usage
>>>>>>>> + *
>>>>>>>> + * See drm_gpuvm_resv_add_fence().
>>>>>>>> + */
>>>>>>>> +static inline void
>>>>>>>> +drm_gpuvm_exec_resv_add_fence(struct drm_gpuvm_exec
>>>>>>>> *vm_exec,
>>>>>>>> +                             struct dma_fence *fence,
>>>>>>>> +                             enum dma_resv_usage
>>>>>>>> private_usage,
>>>>>>>> +                             enum dma_resv_usage
>>>>>>>> extobj_usage)
>>>>>>>> +{
>>>>>>>> +       drm_gpuvm_resv_add_fence(vm_exec->vm, &vm_exec->exec,
>>>>>>>> fence,
>>>>>>>> +                                private_usage,
>>>>>>>> extobj_usage);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>     /**
>>>>>>>>      * struct drm_gpuvm_bo - structure representing a
>>>>>>>> &drm_gpuvm and
>>>>>>>>      * &drm_gem_object combination
>>>>>>>> @@ -398,6 +569,18 @@ struct drm_gpuvm_bo {
>>>>>>>>                           * gpuva list.
>>>>>>>>                           */
>>>>>>>>                          struct list_head gem;
>>>>>>>> +
>>>>>>>> +                       /**
>>>>>>>> +                        * @evict: List entry to attach to
>>>>>>>> the &drm_gpuvms
>>>>>>>> +                        * extobj list.
>>>>>>>> +                        */
>>>>>>>> +                       struct list_head extobj;
>>>>>>>> +
>>>>>>>> +                       /**
>>>>>>>> +                        * @evict: List entry to attach to
>>>>>>>> the &drm_gpuvms evict
>>>>>>>> +                        * list.
>>>>>>>> +                        */
>>>>>>>> +                       struct list_head evict;
>>>>>>>>                  } entry;
>>>>>>>>          } list;
>>>>>>>>     };
>>>>>>>> @@ -432,6 +615,9 @@ struct drm_gpuvm_bo *
>>>>>>>>     drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>>>>>>>                    struct drm_gem_object *obj);
>>>>>>>> +void drm_gpuvm_bo_evict(struct drm_gem_object *obj, bool
>>>>>>>> evict);
>>>>>>>> +void drm_gpuvm_bo_extobj_add(struct drm_gpuvm_bo *vm_bo);
>>>>>>>> +
>>>>>>>>     /**
>>>>>>>>      * drm_gpuvm_bo_for_each_va() - iterator to walk over a
>>>>>>>> list of &drm_gpuva
>>>>>>>>      * @va__: &drm_gpuva structure to assign to in each
>>>>>>>> iteration step
>>>>>>>> @@ -837,6 +1023,17 @@ struct drm_gpuvm_ops {
>>>>>>>>           * used.
>>>>>>>>           */
>>>>>>>>          int (*sm_step_unmap)(struct drm_gpuva_op *op, void
>>>>>>>> *priv);
>>>>>>>> +
>>>>>>>> +       /**
>>>>>>>> +        * @bo_validate: called from drm_gpuvm_validate()
>>>>>>>> +        *
>>>>>>>> +        * Drivers receive this callback for every evicted
>>>>>>>> &drm_gem_object being
>>>>>>>> +        * mapped in the corresponding &drm_gpuvm.
>>>>>>>> +        *
>>>>>>>> +        * Typically, drivers would call their driver
>>>>>>>> specific variant of
>>>>>>>> +        * ttm_bo_validate() from within this callback.
>>>>>>>> +        */
>>>>>>>> +       int (*bo_validate)(struct drm_gem_object *obj);
>>>>>>>>     };
>>>>>>>>     int drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm, void *priv,
>