[Intel-gfx] [PATCH 1/5] drm/i915: Do not define vma on stack

[Dave Airlie]

On Tue, 14 Sept 2021 at 14:55, Matthew Brost <matthew.brost at intel.com> wrote:
>
> From: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota at intel.com>
>
> Defining vma on stack can cause stack overflow, if
> vma gets populated with new fields.

Is there some higher level locking stopping that from getting trashed?
or a guarantee that uc_fw_bind_ggtt is only entered by one thread at a
time?

Dave.

>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota at intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> Reviewed-by: Matthew Brost <matthew.brost at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 18 +++++++++---------
>  drivers/gpu/drm/i915/gt/uc/intel_uc_fw.h |  2 ++
>  2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> index 3a16d08608a5..f632dbd32b42 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> @@ -413,20 +413,20 @@ static void uc_fw_bind_ggtt(struct intel_uc_fw *uc_fw)
>  {
>         struct drm_i915_gem_object *obj = uc_fw->obj;
>         struct i915_ggtt *ggtt = __uc_fw_to_gt(uc_fw)->ggtt;
> -       struct i915_vma dummy = {
> -               .node.start = uc_fw_ggtt_offset(uc_fw),
> -               .node.size = obj->base.size,
> -               .pages = obj->mm.pages,
> -               .vm = &ggtt->vm,
> -       };
> +       struct i915_vma *dummy = &uc_fw->dummy;
> +
> +       dummy->node.start = uc_fw_ggtt_offset(uc_fw);
> +       dummy->node.size = obj->base.size;
> +       dummy->pages = obj->mm.pages;
> +       dummy->vm = &ggtt->vm;
>
>         GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
> -       GEM_BUG_ON(dummy.node.size > ggtt->uc_fw.size);
> +       GEM_BUG_ON(dummy->node.size > ggtt->uc_fw.size);
>
>         /* uc_fw->obj cache domains were not controlled across suspend */
> -       drm_clflush_sg(dummy.pages);
> +       drm_clflush_sg(dummy->pages);
>
> -       ggtt->vm.insert_entries(&ggtt->vm, &dummy, I915_CACHE_NONE, 0);
> +       ggtt->vm.insert_entries(&ggtt->vm, dummy, I915_CACHE_NONE, 0);
>  }
>
>  static void uc_fw_unbind_ggtt(struct intel_uc_fw *uc_fw)
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.h b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.h
> index 99bb1fe1af66..693cc0ebcd63 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.h
> @@ -10,6 +10,7 @@
>  #include "intel_uc_fw_abi.h"
>  #include "intel_device_info.h"
>  #include "i915_gem.h"
> +#include "i915_vma.h"
>
>  struct drm_printer;
>  struct drm_i915_private;
> @@ -75,6 +76,7 @@ struct intel_uc_fw {
>         bool user_overridden;
>         size_t size;
>         struct drm_i915_gem_object *obj;
> +       struct i915_vma dummy;
>
>         /*
>          * The firmware build process will generate a version header file with major and
> --
> 2.32.0
>