@@ -4,6 +4,7 @@ config DRM_I915
depends on X86 && PCI
select INTEL_GTT
select INTERVAL_TREE
+ select STOP_MACHINE
# we need shmfs for the swappable backing store, and in particular
# the shmem_readpage() which depends upon tmpfs
select SHMEM
@@ -735,6 +735,8 @@ struct drm_i915_error_state {
struct kref ref;
struct timeval time;
+ struct drm_i915_private *i915;
+
char error_msg[128];
bool simulated;
int iommu;
@@ -28,6 +28,7 @@
*/
#include <generated/utsrelease.h>
+#include <linux/stop_machine.h>
#include "i915_drv.h"
#ifdef CONFIG_DRM_I915_CAPTURE_ERROR
@@ -720,14 +721,12 @@ i915_error_object_create(struct drm_i915_private *dev_priv,
dst->page_count = num_pages;
while (num_pages--) {
- unsigned long flags;
void *d;
d = kmalloc(PAGE_SIZE, GFP_ATOMIC);
if (d == NULL)
goto unwind;
- local_irq_save(flags);
if (use_ggtt) {
void __iomem *s;
@@ -746,15 +745,10 @@ i915_error_object_create(struct drm_i915_private *dev_priv,
page = i915_gem_object_get_page(src, i);
- drm_clflush_pages(&page, 1);
-
s = kmap_atomic(page);
memcpy(d, s, PAGE_SIZE);
kunmap_atomic(s);
-
- drm_clflush_pages(&page, 1);
}
- local_irq_restore(flags);
dst->pages[i++] = d;
reloc_offset += PAGE_SIZE;
@@ -1420,6 +1414,31 @@ static void i915_capture_gen_state(struct drm_i915_private *dev_priv,
sizeof(error->device_info));
}
+static int capture(void *data)
+{
+ struct drm_i915_error_state *error = data;
+
+ /* Ensure that what we readback from memory matches what the GPU sees */
+ wbinvd();
+
+ i915_capture_gen_state(error->i915, error);
+ i915_capture_reg_state(error->i915, error);
+ i915_gem_record_fences(error->i915, error);
+ i915_gem_record_rings(error->i915, error);
+ i915_capture_active_buffers(error->i915, error);
+ i915_capture_pinned_buffers(error->i915, error);
+
+ do_gettimeofday(&error->time);
+
+ error->overlay = intel_overlay_capture_error_state(error->i915);
+ error->display = intel_display_capture_error_state(error->i915);
+
+ /* And make sure we don't leave trash in the CPU cache */
+ wbinvd();
+
+ return 0;
+}
+
/**
* i915_capture_error_state - capture an error record for later analysis
* @dev: drm device
@@ -1451,18 +1470,9 @@ void i915_capture_error_state(struct drm_i915_private *dev_priv,
}
kref_init(&error->ref);
+ error->i915 = dev_priv;
- i915_capture_gen_state(dev_priv, error);
- i915_capture_reg_state(dev_priv, error);
- i915_gem_record_fences(dev_priv, error);
- i915_gem_record_rings(dev_priv, error);
- i915_capture_active_buffers(dev_priv, error);
- i915_capture_pinned_buffers(dev_priv, error);
-
- do_gettimeofday(&error->time);
-
- error->overlay = intel_overlay_capture_error_state(dev_priv);
- error->display = intel_display_capture_error_state(dev_priv);
+ stop_machine(capture, error, NULL);
i915_error_capture_msg(dev_priv, error, engine_mask, error_msg);
DRM_INFO("%s\n", error->error_msg);
The error state is purposefully racy as we expect it to be called at any time and so have avoided any locking whilst capturing the crash dump. However, with multi-engine GPUs and multiple CPUs, those races can manifest into OOPSes as we attempt to chase dangling pointers freed on other CPUs. Under discussion are lots of ways to slow down normal operation in order to protect the post-mortem error capture, but what it we take the opposite approach and freeze the machine whilst the error capture runs (note the GPU may still running, but as long as we don't process any of the results the driver's bookkeeping will be static). Note that by of itself, this is not a complete fix. It also depends on the compiler barriers in list_add/list_del to prevent traversing the lists into the void. We also depend that we only require state from carefully controlled sources - i.e. all the state we require for post-mortem debugging should be reachable from the request itself so that we only have to worry about retrieving the request carefully. Once we have the request, we know that all pointers from it are intact. v2: Avoid drm_clflush_pages() inside stop_machine() as it may use stop_machine() itself for its wbinvd fallback. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> --- drivers/gpu/drm/i915/Kconfig | 1 + drivers/gpu/drm/i915/i915_drv.h | 2 ++ drivers/gpu/drm/i915/i915_gpu_error.c | 46 +++++++++++++++++++++-------------- 3 files changed, 31 insertions(+), 18 deletions(-)