On 12/03/2021 14:52, Jason Ekstrand wrote:
On Fri, Mar 12, 2021 at 6:17 AM Matthew Auld
<matthew.william.auld@xxxxxxxxx> wrote:
On Fri, 12 Mar 2021 at 11:47, Tvrtko Ursulin
<tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote:
On 12/03/2021 10:56, Matthew Auld wrote:
On Fri, 12 Mar 2021 at 09:50, Tvrtko Ursulin
<tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote:
On 11/03/2021 18:17, 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.
Making softpin a requirement for all future hardware seems reasonable.
There is one piece of hardware enabled by default in i915: RKL which was
enabled by e22fa6f0a976 which has not yet landed in drm-next so this
almost but not really a userspace API change for RKL. If it becomes a
problem, we can always add !IS_ROCKETLAKE(eb->i915) to the condition.
Rejecting relocations starting with newer Gen12 platforms 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
v4 (Jason Ekstrand):
- Call out Rocket Lake in the commit message
Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
Acked-by: Keith Packard <keithp@xxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
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;
I still recommend ENODEV as more inline with our established error
codes. (Platform does not support vs dear userspace you messed up your
flags, modes, whatever.)
I don't know that I care that much what color we paint this shed. I
just want it decided so we can all move on. Here's a few comments:
-ENODEV, at least based on the DRM error code docs doesn't make much
sense to me because the device is very much still there, you just did
something wrong.
-EOPNOTSUPP I could see but the operation of execbuf is very much
supported, just not with this set of parameters. This makes sense to
me for the removal of pread/pwrite but not here.
-EINVAL is always a correct choice but tells you nothing. On the
other hand, this is what's returned by drm_invalid_op which is what we
use when we entirely delete a feature.
As someone who has spent way too much of their life trying to figure
out why execbuffer is returning -EINVAL, I really don't think one more
makes it any worse. If anything, -EINVAL has the advantage that you
can smash some #defines at the top of the file and get dmesg stuff
which can be pretty useful.
In any case, could we please pick a color so I can send a, hopefully
final, new version. :-)
EINVAL is not the end of the world for me and you have some r-bs and
acks already so your call.
I was simply pointing our how to stay consistent with the other ioctls
in i915. Because to me consistency trumps a lot of other things. So if
we go along the route of ENODEV makes no sense argument, then I wouldn't
be far from suggesting to evaluate all of the existing ones as well.
Regards,
Tvrtko
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