dma-buf provides an interfaces for receiving notifications from DMA hardware, and for implicitly tracking fences used for rendering into dma-buf. We want to be able to use these event sources along with kfence for easy collection and combining with other events.

Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Shuah Khan shuahkh@osg.samsung.com Cc: Tejun Heo tj@kernel.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Andrew Morton akpm@linux-foundation.org Cc: Ingo Molnar mingo@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Thomas Gleixner tglx@linutronix.de Cc: "Paul E. McKenney" paulmck@linux.vnet.ibm.com Cc: Dan Williams dan.j.williams@intel.com Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Nikolay Aleksandrov nikolay@cumulusnetworks.com Cc: "David S. Miller" davem@davemloft.net Cc: "Peter Zijlstra (Intel)" peterz@infradead.org Cc: Rasmus Villemoes linux@rasmusvillemoes.dk Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Alexander Potapenko glider@google.com Cc: linux-kernel@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org --- drivers/dma-buf/fence.c | 58 +++++++++++++++++++++++++++++++++++++++++++ drivers/dma-buf/reservation.c | 48 +++++++++++++++++++++++++++++++++++ include/linux/fence.h | 6 +++++ include/linux/kfence.h | 2 ++ include/linux/reservation.h | 7 ++++++ kernel/kfence.c | 8 ++++++ 6 files changed, 129 insertions(+)

diff --git a/drivers/dma-buf/fence.c b/drivers/dma-buf/fence.c index 7b05dbe9b296..3f06b3b1b4cc 100644 --- a/drivers/dma-buf/fence.c +++ b/drivers/dma-buf/fence.c @@ -22,6 +22,7 @@ #include <linux/export.h> #include <linux/atomic.h> #include <linux/fence.h> +#include <linux/kfence.h>

#define CREATE_TRACE_POINTS #include <trace/events/fence.h> @@ -530,3 +531,60 @@ fence_init(struct fence *fence, const struct fence_ops *ops, trace_fence_init(fence); } EXPORT_SYMBOL(fence_init); + +struct dma_fence_cb { + struct fence_cb base; + struct kfence *fence; +}; + +static void dma_kfence_wake(struct fence *dma, struct fence_cb *data) +{ + struct dma_fence_cb *cb = container_of(data, typeof(*cb), base); + + kfence_complete(cb->fence); + kfence_put(cb->fence); + kfree(cb); +} + +/** + * kfence_await_dma_fence - set the fence to wait upon a DMA fence + * @fence: this kfence + * @dma: target DMA fence to wait upon + * @gfp: the allowed allocation type + * + * kfence_add_dma() causes the @fence to wait upon completion of a DMA fence. + * + * Returns 1 if the @fence was successfully to the waitqueue of @dma, 0 + * if @dma was already signaled (and so not added), or a negative error code. + */ +int kfence_await_dma_fence(struct kfence *fence, struct fence *dma, gfp_t gfp) +{ + struct dma_fence_cb *cb; + int ret; + + if (fence_is_signaled(dma)) + return 0; + + cb = kmalloc(sizeof(*cb), gfp); + if (!cb) { + if (!gfpflags_allow_blocking(gfp)) + return -ENOMEM; + + return fence_wait(dma, false); + } + + cb->fence = kfence_get(fence); + kfence_await(fence); + + ret = fence_add_callback(dma, &cb->base, dma_kfence_wake); + if (ret == 0) { + ret = 1; + } else { + dma_kfence_wake(dma, &cb->base); + if (ret == -ENOENT) /* fence already signaled */ + ret = 0; + } + + return ret; +} +EXPORT_SYMBOL_GPL(kfence_await_dma_fence); diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 9566a62ad8e3..138b792af0c3 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -543,3 +543,51 @@ unlock_retry: goto retry; } EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu); + +/** + * kfence_add_reservation - set the fence to wait upon a reservation_object + * @fence: this kfence + * @resv: target reservation_object (collection of DMA fences) to wait upon + * @write: Wait for read or read/write access + * @gfp: the allowed allocation type + * + * kfence_add_reservation() causes the @fence to wait upon completion of the + * reservation object (a collection of DMA fences), either for read access + * or for read/write access. + * + * Returns 1 if the @fence was successfully to the waitqueues of @resv, 0 + * if @resev was already signaled (and so not added), or a negative error code. + */ +int kfence_await_reservation(struct kfence *fence, + struct reservation_object *resv, + bool write, + gfp_t gfp) +{ + struct fence *excl, **shared; + unsigned int count, i; + int ret; + + ret = reservation_object_get_fences_rcu(resv, &excl, &count, &shared); + if (ret) + return ret; + + if (write) { + for (i = 0; i < count; i++) { + ret |= kfence_await_dma_fence(fence, shared[i], gfp); + if (ret < 0) + goto out; + } + } + + if (excl) + ret |= kfence_await_dma_fence(fence, excl, gfp); + +out: + fence_put(excl); + for (i = 0; i < count; i++) + fence_put(shared[i]); + kfree(shared); + + return ret; +} +EXPORT_SYMBOL_GPL(kfence_await_reservation); diff --git a/include/linux/fence.h b/include/linux/fence.h index 2056e9fd0138..3c3bc318e826 100644 --- a/include/linux/fence.h +++ b/include/linux/fence.h @@ -34,6 +34,8 @@ struct fence; struct fence_ops; struct fence_cb;

+struct kfence; + /** * struct fence - software synchronization primitive * @refcount: refcount for this fence @@ -378,4 +380,8 @@ unsigned fence_context_alloc(unsigned num); ##args); \ } while (0)

+int kfence_await_dma_fence(struct kfence *fence, + struct fence *dma, + gfp_t gfp); + #endif /* __LINUX_FENCE_H */ diff --git a/include/linux/kfence.h b/include/linux/kfence.h index 76a2f95dfb70..acbfc2ea7c49 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -16,6 +16,8 @@ #include <linux/wait.h>

struct completion; +struct fence; +struct reservation_object; enum hrtimer_mode;

struct kfence { diff --git a/include/linux/reservation.h b/include/linux/reservation.h index b0f305e77b7f..1954bab95db9 100644 --- a/include/linux/reservation.h +++ b/include/linux/reservation.h @@ -49,6 +49,8 @@ extern struct ww_class reservation_ww_class; extern struct lock_class_key reservation_seqcount_class; extern const char reservation_seqcount_string[];

+struct kfence; + /** * struct reservation_object_list - a list of shared fences * @rcu: for internal use @@ -210,4 +212,9 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, bool reservation_object_test_signaled_rcu(struct reservation_object *obj, bool test_all);

+int kfence_await_reservation(struct kfence *fence, + struct reservation_object *resv, + bool write, + gfp_t gfp); + #endif /* _LINUX_RESERVATION_H */ diff --git a/kernel/kfence.c b/kernel/kfence.c index 59c27910a749..4605eabc2c1b 100644 --- a/kernel/kfence.c +++ b/kernel/kfence.c @@ -7,7 +7,9 @@ * of the License. */

+#include <linux/fence.h> #include <linux/kfence.h> +#include <linux/reservation.h> #include <linux/slab.h>

/** @@ -51,6 +53,12 @@ * - kfence_await_hrtimer(): the kfence asynchronously wait for an expiration * of a timer * + * - kfence_await_dma_fence(): the kfence asynchronously waits for a DMA + * (hardware signaled) fence + * + * - kfence_await_reservation(): the kfence asynchronously waits for a DMA + * reservation object + * * A kfence is initialised using kfence_init(), and starts off awaiting an * event. Once you have finished setting up the fence, including adding * all of its asynchronous waits, call kfence_complete().