Re: [Intel-gfx] [PATCH] i915: Drop relocation support on all new hardware (v3)

On 10/03/2021 21:50, Jason Ekstrand wrote:

The Vulkan driver in Mesa for Intel hardware never uses relocations if it's running on a version of i915 that supports at least softpin which all versions of i915 supporting Gen12 do. On the OpenGL side, Gen12+ is only supported by iris which never uses relocations. The older i965 driver in Mesa does use relocations but it only supports Intel hardware through Gen11 and has been deprecated for all hardware Gen9+. The compute driver also never uses relocations. This only leaves the media driver which is supposed to be switching to softpin going forward.

How does "supposed to be" translates to actually being ready? Cc someone from media so they can ack?

Making softpin a requirement for all future hardware seems reasonable.

Rejecting relocations starting with Gen12 has the benefit that we don't have to bother supporting it on platforms with local memory. Given how much CPU touching of memory is required for relocations, not having to do so on platforms where not all memory is directly CPU-accessible carries significant advantages.

v2 (Jason Ekstrand):

• Allow TGL-LP platforms as they've already shipped

v3 (Jason Ekstrand):

• WARN_ON platforms with LMEM support in case the check is wrong

Signed-off-by: Jason Ekstrand jason@jlekstrand.net Cc: Dave Airlie airlied@redhat.com Cc: Daniel Vetter daniel.vetter@intel.com

---

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 99772f37bff60..b02dbd16bfa03 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -1764,7 +1764,8 @@ eb_relocate_vma_slow(struct i915_execbuffer *eb, struct eb_vma *ev) return err; }

-static int check_relocations(const struct drm_i915_gem_exec_object2 *entry) +static int check_relocations(const struct i915_execbuffer *eb,

• 	     const struct drm_i915_gem_exec_object2 *entry)
  

  { const char __user *addr, *end; unsigned long size;

@@ -1774,6 +1775,14 @@ static int check_relocations(const struct drm_i915_gem_exec_object2 *entry) if (size == 0) return 0;

• /* Relocations are disallowed for all platforms after TGL-LP */
• if (INTEL_GEN(eb->i915) >= 12 && !IS_TIGERLAKE(eb->i915))

• return -EINVAL;
  

• /* All discrete memory platforms are Gen12 or above */
• if (WARN_ON(HAS_LMEM(eb->i915)))

• return -EINVAL;
  

Maybe ENODEV as our more typical "this platform does not support this" instead of "you are using it wrong".

Regards,

Tvrtko

• if (size > N_RELOC(ULONG_MAX)) return -EINVAL;

@@ -1807,7 +1816,7 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) if (nreloc == 0) continue;

• err = check_relocations(&eb->exec[i]);
  

• err = check_relocations(eb, &eb->exec[i]);
  

  if (err) goto err;

@@ -1880,7 +1889,7 @@ static int eb_prefault_relocations(const struct i915_execbuffer *eb) for (i = 0; i < count; i++) { int err;

• err = check_relocations(&eb->exec[i]);
  

• err = check_relocations(eb, &eb->exec[i]);
  

  if (err) return err; }