[PATCH i-g-t, v2 4/6] lib/intel_compute: Allow the user to provide a custom compute kernel

[Francois Dugast]

Allow the user to provide a custom compute kernel which will be used
instead of the default compute square one. This custom kernel _must_
fulfill requirements specified in the user_execenv::kernel doc. IGT
does not provide a complete runtime which can run generic kernels.

Allowing custom compute kernels gives us the possibility to leverage
the existing lib/intel_compute infrastructure to test corner cases.
More complex KMD tests will require simple specific compute kernels.
For example this one can trigger a page fault at 0x10000 from the
compute kernel context, so that we run other checks in KMD, all from
IGT:

    __kernel void square(__global float* input,
                         __global float* output,
                         const unsigned int count) {
        int i = get_global_id(0);
        const __global uint* addr = 0x10000;
        output[i] = *addr;
    }

v2: Improve documentation and commit message

Signed-off-by: Francois Dugast <francois.dugast at intel.com>
---
 lib/intel_compute.c | 26 ++++++++++++++++++--------
 lib/intel_compute.h | 14 ++++++++++++++
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/lib/intel_compute.c b/lib/intel_compute.c
index cad932c24..04fb83321 100644
--- a/lib/intel_compute.c
+++ b/lib/intel_compute.c
@@ -1778,6 +1778,8 @@ static bool __run_intel_compute_kernel(int fd,
 	unsigned int batch;
 	const struct intel_compute_kernels *kernels = intel_compute_square_kernels;
 	enum intel_driver driver = get_intel_driver(fd);
+	const unsigned char *kernel;
+	unsigned int kernel_size;
 
 	for (batch = 0; batch < ARRAY_SIZE(intel_compute_batches); batch++) {
 		if (ip_ver == intel_compute_batches[batch].ip_ver)
@@ -1795,16 +1797,24 @@ static bool __run_intel_compute_kernel(int fd,
 		return false;
 	}
 
-	while (kernels->kernel) {
-		if (ip_ver == kernels->ip_ver)
-			break;
-		kernels++;
+	/* If the user provides a kernel, use it */
+	if (user && user->kernel) {
+		kernel = user->kernel;
+		kernel_size = user->kernel_size;
+	} else {
+		while (kernels->kernel) {
+			if (ip_ver == kernels->ip_ver)
+				break;
+			kernels++;
+		}
+		if (!kernels->kernel)
+			return false;
+		kernel = kernels->kernel;
+		kernel_size = kernels->size;
 	}
-	if (!kernels->kernel)
-		return false;
 
-	intel_compute_batches[batch].compute_exec(fd, kernels->kernel,
-						  kernels->size, eci, user);
+	intel_compute_batches[batch].compute_exec(fd, kernel,
+						  kernel_size, eci, user);
 
 	return true;
 }
diff --git a/lib/intel_compute.h b/lib/intel_compute.h
index 62e2422c4..3f6d0bb1d 100644
--- a/lib/intel_compute.h
+++ b/lib/intel_compute.h
@@ -39,6 +39,20 @@ struct intel_compute_kernels {
 struct user_execenv {
 	/** @vm: use this VM if provided, otherwise create one */
 	uint32_t vm;
+	/**
+	 * @kernel: use this custom kernel if provided, otherwise use a default square kernel
+	 *
+	 * Custom kernel execution in lib/intel_compute has strong limitations, it does not
+	 * allow running any custom kernel. "count" is the size of the input and output arrays
+	 * and the provided kernel must have the following prototype:
+	 *
+	 *    __kernel void square(__global float* input,
+	 *                         __global float* output,
+	 *                         const unsigned int count)
+	 */
+	const unsigned char *kernel;
+	/** @kernel_size: size of the custom kernel, if provided */
+	unsigned int kernel_size;
 };
 
 extern const struct intel_compute_kernels intel_compute_square_kernels[];
-- 
2.43.0