Re: [PATCH 1/2] drm/i915: Check for scratch page scribbling

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Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:

> Periodically check, for example when idling and upon closing user
> contexts, whether or not some client has written into unallocated PTE in
> their ppGTT.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
>  .../drm/i915/gem/selftests/i915_gem_context.c | 19 +++++++--
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 31 +-------------
>  drivers/gpu/drm/i915/gt/intel_gt_pm.c         |  4 ++
>  drivers/gpu/drm/i915/gt/intel_gtt.c           | 42 +++++++++++++++++++
>  drivers/gpu/drm/i915/gt/intel_gtt.h           |  1 +
>  drivers/gpu/drm/i915/i915_scheduler.c         | 33 +--------------
>  drivers/gpu/drm/i915/i915_utils.c             | 29 +++++++++++++
>  drivers/gpu/drm/i915/i915_utils.h             |  3 ++
>  8 files changed, 98 insertions(+), 64 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> index df949320f2b5..b0c349a46e6a 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> @@ -1737,7 +1737,7 @@ static int read_from_scratch(struct i915_gem_context *ctx,
>  	return err;
>  }
>  
> -static int check_scratch_page(struct i915_gem_context *ctx, u32 *out)
> +static int check_ctx_scratch(struct i915_gem_context *ctx, u32 *out)
>  {
>  	struct i915_address_space *vm;
>  	struct page *page;
> @@ -1770,6 +1770,17 @@ static int check_scratch_page(struct i915_gem_context *ctx, u32 *out)
>  	return err;
>  }
>  
> +static void reset_ctx_scratch(struct i915_gem_context *ctx, u32 value)
> +{
> +	struct i915_address_space *vm = ctx_vm(ctx);
> +	struct page *page = __px_page(vm->scratch[0]);
> +	u32 *vaddr;
> +
> +	vaddr = kmap(page);
> +	memset32(vaddr, value, PAGE_SIZE / sizeof(value));
> +	kunmap(page);
> +}
> +
>  static int igt_vm_isolation(void *arg)
>  {
>  	struct drm_i915_private *i915 = arg;
> @@ -1816,11 +1827,11 @@ static int igt_vm_isolation(void *arg)
>  		goto out_file;
>  
>  	/* Read the initial state of the scratch page */
> -	err = check_scratch_page(ctx_a, &expected);
> +	err = check_ctx_scratch(ctx_a, &expected);
>  	if (err)
>  		goto out_file;
>  
> -	err = check_scratch_page(ctx_b, &expected);
> +	err = check_ctx_scratch(ctx_b, &expected);
>  	if (err)
>  		goto out_file;
>  
> @@ -1876,6 +1887,8 @@ static int igt_vm_isolation(void *arg)
>  		count, num_engines);
>  
>  out_file:
> +	/* As we deliberately write into scratch, cover up our tracks */
> +	reset_ctx_scratch(ctx_a, expected);
>  	if (igt_live_test_end(&t))
>  		err = -EIO;
>  	fput(file);
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 577ebd4a324f..8443794df3ee 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -1265,35 +1265,6 @@ bool intel_engine_can_store_dword(struct intel_engine_cs *engine)
>  	}
>  }
>  
> -static void hexdump(struct drm_printer *m, const void *buf, size_t len)
> -{
> -	const size_t rowsize = 8 * sizeof(u32);
> -	const void *prev = NULL;
> -	bool skip = false;
> -	size_t pos;
> -
> -	for (pos = 0; pos < len; pos += rowsize) {
> -		char line[128];
> -
> -		if (prev && !memcmp(prev, buf + pos, rowsize)) {
> -			if (!skip) {
> -				drm_printf(m, "*\n");
> -				skip = true;
> -			}
> -			continue;
> -		}
> -
> -		WARN_ON_ONCE(hex_dump_to_buffer(buf + pos, len - pos,
> -						rowsize, sizeof(u32),
> -						line, sizeof(line),
> -						false) >= sizeof(line));
> -		drm_printf(m, "[%04zx] %s\n", pos, line);
> -
> -		prev = buf + pos;
> -		skip = false;
> -	}
> -}
> -
>  static void intel_engine_print_registers(struct intel_engine_cs *engine,
>  					 struct drm_printer *m)
>  {
> @@ -1450,7 +1421,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
>  	}
>  
>  	drm_printf(m, "HWSP:\n");
> -	hexdump(m, engine->status_page.addr, PAGE_SIZE);
> +	i915_hexdump(m, engine->status_page.addr, PAGE_SIZE);
>  
>  	drm_printf(m, "Idle? %s\n", yesno(intel_engine_is_idle(engine)));
>  
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> index 0bd303d2823e..38375a006a99 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> @@ -11,6 +11,7 @@
>  #include "intel_context.h"
>  #include "intel_engine_pm.h"
>  #include "intel_gt.h"
> +#include "intel_gtt.h"
>  #include "intel_gt_clock_utils.h"
>  #include "intel_gt_pm.h"
>  #include "intel_gt_requests.h"
> @@ -100,6 +101,9 @@ static int __gt_park(struct intel_wakeref *wf)
>  	runtime_end(gt);
>  	intel_gt_park_requests(gt);
>  
> +	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> +		check_scratch_page(gt->vm);
> +
>  	i915_vma_parked(gt);
>  	i915_pmu_gt_parked(i915);
>  	intel_rps_park(&gt->rps);
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
> index d34770ae4c9a..5ac9eb4a3a92 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
> @@ -158,10 +158,49 @@ static void poison_scratch_page(struct drm_i915_gem_object *scratch)
>  
>  		vaddr = kmap(page);
>  		memset(vaddr, val, PAGE_SIZE);
> +		set_page_dirty(page); /* keep the poisoned contents */

Should we use locked version in here?

-Mika

>  		kunmap(page);
>  	}
>  }
>  
> +void check_scratch_page(const struct i915_address_space *vm)
> +{
> +	struct drm_i915_gem_object *scratch;
> +	struct sgt_iter sgt;
> +	struct page *page;
> +	void *vaddr;
> +	u8 val;
> +
> +	scratch = vm->scratch[0];
> +	if (!scratch || !i915_gem_object_has_struct_page(scratch))
> +		return;
> +
> +	val = 0;
> +	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> +		val = POISON_FREE;
> +
> +	for_each_sgt_page(page, sgt, scratch->mm.pages) {
> +		vaddr = kmap(page);
> +		drm_clflush_virt_range(vaddr, PAGE_SIZE);
> +		if (memchr_inv(vaddr, val, PAGE_SIZE)) {
> +			struct drm_printer p = drm_err_printer(__func__);
> +
> +			drm_err(&vm->i915->drm,
> +				"%s scratch page overwitten!\n",
> +				i915_is_ggtt(vm) ? "Global" : "Per-process");
> +			i915_hexdump(&p, vaddr, PAGE_SIZE);
> +			vaddr = NULL;
> +		}
> +		kunmap(page);
> +		if (!vaddr)
> +			break;
> +	}
> +
> +	/* Restore the poison, so fresh errors will be detected */
> +	if (!vaddr)
> +		poison_scratch_page(scratch);
> +}
> +
>  int setup_scratch_page(struct i915_address_space *vm)
>  {
>  	unsigned long size;
> @@ -229,6 +268,9 @@ void free_scratch(struct i915_address_space *vm)
>  {
>  	int i;
>  
> +	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> +		check_scratch_page(vm);
> +
>  	for (i = 0; i <= vm->top; i++)
>  		i915_gem_object_put(vm->scratch[i]);
>  }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
> index 24b5808df16d..a5b312c6485a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
> @@ -519,6 +519,7 @@ fill_page_dma(struct drm_i915_gem_object *p, const u64 val, unsigned int count);
>  } while (0)
>  
>  int setup_scratch_page(struct i915_address_space *vm);
> +void check_scratch_page(const struct i915_address_space *vm);
>  void free_scratch(struct i915_address_space *vm);
>  
>  struct drm_i915_gem_object *alloc_pt_dma(struct i915_address_space *vm, int sz);
> diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
> index a8fb787278e6..7241f85c9967 100644
> --- a/drivers/gpu/drm/i915/i915_scheduler.c
> +++ b/drivers/gpu/drm/i915/i915_scheduler.c
> @@ -1095,35 +1095,6 @@ void i915_request_show_with_schedule(struct drm_printer *m,
>  	rcu_read_unlock();
>  }
>  
> -static void hexdump(struct drm_printer *m, const void *buf, size_t len)
> -{
> -	const size_t rowsize = 8 * sizeof(u32);
> -	const void *prev = NULL;
> -	bool skip = false;
> -	size_t pos;
> -
> -	for (pos = 0; pos < len; pos += rowsize) {
> -		char line[128];
> -
> -		if (prev && !memcmp(prev, buf + pos, rowsize)) {
> -			if (!skip) {
> -				drm_printf(m, "*\n");
> -				skip = true;
> -			}
> -			continue;
> -		}
> -
> -		WARN_ON_ONCE(hex_dump_to_buffer(buf + pos, len - pos,
> -						rowsize, sizeof(u32),
> -						line, sizeof(line),
> -						false) >= sizeof(line));
> -		drm_printf(m, "[%04zx] %s\n", pos, line);
> -
> -		prev = buf + pos;
> -		skip = false;
> -	}
> -}
> -
>  static void
>  print_request_ring(struct drm_printer *m, const struct i915_request *rq)
>  {
> @@ -1153,7 +1124,7 @@ print_request_ring(struct drm_printer *m, const struct i915_request *rq)
>  		}
>  		memcpy(ring + len, vaddr + head, size - len);
>  
> -		hexdump(m, ring, size);
> +		i915_hexdump(m, ring, size);
>  		kfree(ring);
>  	}
>  }
> @@ -1195,7 +1166,7 @@ void i915_sched_show(struct drm_printer *m,
>  
>  		if (rq->context->lrc_reg_state) {
>  			drm_printf(m, "Logical Ring Context:\n");
> -			hexdump(m, rq->context->lrc_reg_state, PAGE_SIZE);
> +			i915_hexdump(m, rq->context->lrc_reg_state, PAGE_SIZE);
>  		}
>  	}
>  
> diff --git a/drivers/gpu/drm/i915/i915_utils.c b/drivers/gpu/drm/i915/i915_utils.c
> index 894de60833ec..432ad0926586 100644
> --- a/drivers/gpu/drm/i915/i915_utils.c
> +++ b/drivers/gpu/drm/i915/i915_utils.c
> @@ -49,6 +49,35 @@ __i915_printk(struct drm_i915_private *dev_priv, const char *level,
>  	}
>  }
>  
> +void i915_hexdump(struct drm_printer *m, const void *buf, size_t len)
> +{
> +	const size_t rowsize = 8 * sizeof(u32);
> +	const void *prev = NULL;
> +	bool skip = false;
> +	size_t pos;
> +
> +	for (pos = 0; pos < len; pos += rowsize) {
> +		char line[128];
> +
> +		if (prev && !memcmp(prev, buf + pos, rowsize)) {
> +			if (!skip) {
> +				drm_printf(m, "*\n");
> +				skip = true;
> +			}
> +			continue;
> +		}
> +
> +		WARN_ON_ONCE(hex_dump_to_buffer(buf + pos, len - pos,
> +						rowsize, sizeof(u32),
> +						line, sizeof(line),
> +						false) >= sizeof(line));
> +		drm_printf(m, "[%04zx] %s\n", pos, line);
> +
> +		prev = buf + pos;
> +		skip = false;
> +	}
> +}
> +
>  void add_taint_for_CI(struct drm_i915_private *i915, unsigned int taint)
>  {
>  	__i915_printk(i915, KERN_NOTICE, "CI tainted:%#x by %pS\n",
> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
> index 4618fe8aacb5..c82461d6ae71 100644
> --- a/drivers/gpu/drm/i915/i915_utils.h
> +++ b/drivers/gpu/drm/i915/i915_utils.h
> @@ -32,6 +32,7 @@
>  #include <linux/workqueue.h>
>  
>  struct drm_i915_private;
> +struct drm_printer;
>  struct timer_list;
>  
>  #define FDO_BUG_URL "https://gitlab.freedesktop.org/drm/intel/-/wikis/How-to-file-i915-bugs";
> @@ -82,6 +83,8 @@ bool i915_error_injected(void);
>  	__i915_printk(i915, i915_error_injected() ? KERN_DEBUG : KERN_ERR, \
>  		      fmt, ##__VA_ARGS__)
>  
> +void i915_hexdump(struct drm_printer *m, const void *buf, size_t len);
> +
>  #if defined(GCC_VERSION) && GCC_VERSION >= 70000
>  #define add_overflows_t(T, A, B) \
>  	__builtin_add_overflow_p((A), (B), (T)0)
> -- 
> 2.20.1
>
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> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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