On 25/02/16 11:32, Chris Wilson wrote:
On Thu, Feb 25, 2016 at 11:12:06AM +0000, Daniele Ceraolo Spurio wrote:
On 25/02/16 10:41, Chris Wilson wrote:
On Thu, Feb 25, 2016 at 10:32:11AM +0000, daniele.ceraolospurio@xxxxxxxxx wrote:
+/* This test covers the case where we end up in an uninitialised area of the
+ * ppgtt at an offset greater than the one where the last buffer is mapped. This
+ * is particularly relevant if 48b ppgtt is enabled because the ppgtt is
+ * massively bigger compared to the 32b case and it takes a lot more time to
+ * wrap, so the acthd can potentially keep increasing for a long time
+ */
+#define NSEC_PER_SEC 1000000000L
+static void ppgtt_walking(void)
+{
+ int fd;
+ int64_t timeout_ns = 100 * NSEC_PER_SEC; /* 100 seconds */
This needs a note that this has to be greater than ~5*hangcheck.
+ struct drm_i915_gem_execbuffer2 execbuf;
+ struct drm_i915_gem_exec_object2 gem_exec;
+ uint32_t handle;
+ uint32_t batch[4];
+
+ fd = drm_open_driver(DRIVER_INTEL);
+ igt_require(gem_gtt_type(fd) > 2);
Nope, just full-ppgtt is required (and provides a sensible hangcheck
test if !48bit as well).
Note this does require that the hangcheck is enabled, so igt_require().
+
+ /* the batch will be mapped to an offset < 4GB because the flag to allow
+ * 48b offsets is not specified, so jump to address 0x00000001 00000000
+ */
+ batch[0] = MI_BATCH_BUFFER_START | 1;
+ batch[1] = 0;
+ batch[2] = 1;
+ batch[3] = MI_BATCH_BUFFER_END;
The vm is entirely empty. Just submit an unterminated (empty) batch, and
it will walk from 0 to 1<<48bit and around and around and around and
around...
I chose to jump instead of just leaving the batch unterminated to
cover the (rare) case where the rest of the allocated 4k of the
batch contain some random values, which could cause a hang and thus
falsely pass the test.
That would be a huge kernel bug. Freshly allocated buffers have to be
zero to avoid information leaks. I hope you are confusing allocating
from the userspace buffer cache with a fresh kernel allocation...
-Chris
Apologies for the confusion, you're correct I was thinking about it from
a libdrm level and not from a bare kernel level.
Daniele
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
