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

Thomas Hellström
2023-09-19T15:23:20Z

On 9/19/23 17:16, Danilo Krummrich wrote:
> On 9/19/23 14:21, Thomas Hellström wrote:
>> Hi Christian
>>
>> On 9/19/23 14:07, Christian König wrote:
>>> Am 13.09.23 um 17:46 schrieb Danilo Krummrich:
>>>> On 9/13/23 17:33, Christian König wrote:
>>>>> Am 13.09.23 um 17:15 schrieb Danilo Krummrich:
>>>>>> 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.
>>>>>
>>>>> Well the question is which dma-resv lock do we hold?
>>>>>
>>>>> In the move callback we only hold the dma-resv lock of the BO
>>>>> which is moved, but when that is a shared BO then that's not the
>>>>> same as the one for the VM.
>>>>
>>>> Correct, Thomas' idea was to use the GEM's dma_resv lock to protect
>>>> drm_gpuvm_bo::evicted
>>>> and then actually move the drm_gpuvm_bo to the VM's evicted list
>>>> once we grabbed all
>>>> dma-resv locks when locking the VM's BOs using drm_exec. We can
>>>> remove them from the evicted
>>>> list on validate(). This way we never touch the evicted list
>>>> without holding at least the VM's
>>>> dma-resv lock.
>>>>
>>>> Do you have any concerns about that?
>>>
>>> Scratching my head a bit how that is supposed to work.
>>>
>>> This implies that you go over all the evicted BOs during validation
>>> and not just the one mentioned in the CS.
>>>
>>> That might work for Vulkan, but is pretty much a no-go for OpenGL.
>>>
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> 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.
>>>>>
>>>>> Sorry for the confusion we use different terminology in amdgpu.
>>>>>
>>>>> The eviction lock and evicted state is for the VM page tables,
>>>>> e.g. if the whole VM is currently not used and swapped out or even
>>>>> de-allocated.
>>>>>
>>>>> This is necessary because we have cases where we need to access
>>>>> the VM data without holding the dma-resv lock of this VM.
>>>>> Especially figuring out which parts of an address space contain
>>>>> mappings and which doesn't.
>>>>
>>>> I think this is fine, this has nothing to do with lists of evicted
>>>> GEM objects or external GEM
>>>> objects, right? Marking mappings (drm_gpuva) as invalidated
>>>> (DRM_GPUVA_INVALIDATED) or accessing
>>>> the VA space does not require any dma-resv locks.
>>>
>>> I hope so, but I'm not 100% sure.
>>>
>>>>
>>>>>
>>>>> This is a requirement which comes with HMM handling, you won't see
>>>>> this with Vulkan (or OpenGL, VAAPI etc..).
>>>>>
>>>>>
>>>>> The invalidation lock on the other hand is what in this discussion
>>>>> is called eviction lock. This one is needed because what I wrote
>>>>> above, during the move callback only the dma-resv of the BO which
>>>>> is moved is locked, but not necessarily the dma-resv of the VM.
>>>>
>>>> That's yet another thing, right? This is used to track whether
>>>> *any* BO that belongs to the VM is
>>>> currently being evicted, correct? As mentioned, as by now this is
>>>> not supported in GPUVM and hence
>>>> would be the same driver specific code with the same driver specifc
>>>> lock.
>>>
>>> That is most likely a show stopper using this for OpenGL based
>>> workloads as far as I can see. For those you need to able to figure
>>> out which non-VM BOs have been evicted and which parts of the VM
>>> needs updates.
>>
>> We identify those with a bool in the gpuvm_bo, and that bool is
>> protected by the bo_resv. In essence, the "evicted" list must be made
>> up-to-date with all relevant locks held before traversing in the next
>> exec.
>
> What I still miss with this idea is how do we find all the
> drm_gpuvm_bo structures with the evicted bool set to true? When doing
> the drm_exec dance we come across all external ones and can add them
> to the list if needed, but what about the BOs having the VM's dma-resv?

Oh, they can be added to the evict list directly (no bool needed) in the
eviction code, like in v3. Since for those we indeed hold the VM's
dma_resv since it's aliased with the object's dma-resv.

/Thomas

>
>>
>> If you mean that we need to unbind all vmas of all vms of evicted bos
>> before evicting, We don't do that, at least not in Xe, since evicting
>> we wait for VM idle, and it cant access anything through the stale
>> vmas until they have been revalidated and rebound.
>>
>> /Thomas
>>
>>
>>
>>>>
>>>>>
>>>>> Regards,
>>>>> Christian.
>>>>>
>>>>>>
>>>>>>>
>>>>>>> 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,
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>