Re: [PATCH drm-misc-next v3 6/7] drm/gpuvm: generalize dma_resv/extobj handling and GEM validation
From: Danilo Krummrich
Date: Tue Sep 19 2023 - 11:17:35 EST
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 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?
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@xxxxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
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,