[PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dave Airlie]

On Thu, 4 Jan 2024 at 00:47, Dan Carpenter <dan.carpenter at linaro.org> wrote:
>
> Hi Dave,
>
> kernel test robot noticed the following build warnings:
>
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
> base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
> patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
> patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
> config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
> compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp at intel.com>
> | Reported-by: Dan Carpenter <dan.carpenter at linaro.org>
> | Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/

This is a false positive, I think the code is operating like I'd
expect, we maybe could restructure it to avoid this warning?

The idea is you send an rpc msg, if there's a reply you get a reply,
if no reply you get NULL and if an error you get an error.

So in the case you get an error or NULL you just want to return 0 for
the NULL as it's successful, and error otherwise.

Would using PTR_ERR_OR_ZERO make smatch happy? (even if it's not
really what we want).

Dave.
>
> New smatch warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:659 r535_gsp_rpc_rm_ctrl_push() warn: passing zero to 'PTR_ERR'
> drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c:1063 r535_dp_aux_xfer() warn: passing a valid pointer to 'PTR_ERR'
>
> Old smatch warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1887 nvkm_gsp_radix3_sg() error: uninitialized symbol 'addr'.
>
> vim +/PTR_ERR +659 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
>
> af265ee961627a Dave Airlie 2023-12-22  649  static int
> af265ee961627a Dave Airlie 2023-12-22  650  r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void **argv, u32 repc)
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  651  {
> af265ee961627a Dave Airlie 2023-12-22  652      rpc_gsp_rm_control_v03_00 *rpc = container_of((*argv), typeof(*rpc), params);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  653      struct nvkm_gsp *gsp = object->client->gsp;
> af265ee961627a Dave Airlie 2023-12-22  654      int ret = 0;
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  655
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  656      rpc = nvkm_gsp_rpc_push(gsp, rpc, true, repc);
> af265ee961627a Dave Airlie 2023-12-22  657      if (IS_ERR_OR_NULL(rpc)) {
> af265ee961627a Dave Airlie 2023-12-22  658              *argv = NULL;
> af265ee961627a Dave Airlie 2023-12-22 @659              return PTR_ERR(rpc);
>
> If nvkm_gsp_rpc_push() returns NULL (probably a failure) then this
> returns PTR_ERR(NULL) which is zero/success.
>
> af265ee961627a Dave Airlie 2023-12-22  660      }
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  661
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  662      if (rpc->status) {
> af265ee961627a Dave Airlie 2023-12-22  663              ret = r535_rpc_status_to_errno(rpc->status);
> 555bb9c29a45be Dave Airlie 2023-12-22  664              if (ret != -EAGAIN)
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  665                      nvkm_error(&gsp->subdev, "cli:0x%08x obj:0x%08x ctrl cmd:0x%08x failed: 0x%08x\n",
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  666                                 object->client->object.handle, object->handle, rpc->cmd, rpc->status);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  667      }
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  668
> af265ee961627a Dave Airlie 2023-12-22  669      if (repc)
> af265ee961627a Dave Airlie 2023-12-22  670              *argv = rpc->params;
> af265ee961627a Dave Airlie 2023-12-22  671      else
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  672              nvkm_gsp_rpc_done(gsp, rpc);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  673
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  674      return ret;
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  675  }
>
> --
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> https://github.com/intel/lkp-tests/wiki
>