[PATCH] vmwgfx: Create debugfs ttm_resource_manager entry only if needed

[Zack Rusin]

On Tue, Mar 12, 2024 at 5:36 AM Jocelyn Falempe <jfalempe at redhat.com> wrote:
>
> The driver creates /sys/kernel/debug/dri/0/mob_ttm even when the
> corresponding ttm_resource_manager is not allocated.
> This leads to a crash when trying to read from this file.
>
> Add a check to create mob_ttm, system_mob_ttm, and gmr_ttm debug file
> only when the corresponding ttm_resource_manager is allocated.
>
> crash> bt
> PID: 3133409  TASK: ffff8fe4834a5000  CPU: 3    COMMAND: "grep"
>  #0 [ffffb954506b3b20] machine_kexec at ffffffffb2a6bec3
>  #1 [ffffb954506b3b78] __crash_kexec at ffffffffb2bb598a
>  #2 [ffffb954506b3c38] crash_kexec at ffffffffb2bb68c1
>  #3 [ffffb954506b3c50] oops_end at ffffffffb2a2a9b1
>  #4 [ffffb954506b3c70] no_context at ffffffffb2a7e913
>  #5 [ffffb954506b3cc8] __bad_area_nosemaphore at ffffffffb2a7ec8c
>  #6 [ffffb954506b3d10] do_page_fault at ffffffffb2a7f887
>  #7 [ffffb954506b3d40] page_fault at ffffffffb360116e
>     [exception RIP: ttm_resource_manager_debug+0x11]
>     RIP: ffffffffc04afd11  RSP: ffffb954506b3df0  RFLAGS: 00010246
>     RAX: ffff8fe41a6d1200  RBX: 0000000000000000  RCX: 0000000000000940
>     RDX: 0000000000000000  RSI: ffffffffc04b4338  RDI: 0000000000000000
>     RBP: ffffb954506b3e08   R8: ffff8fee3ffad000   R9: 0000000000000000
>     R10: ffff8fe41a76a000  R11: 0000000000000001  R12: 00000000ffffffff
>     R13: 0000000000000001  R14: ffff8fe5bb6f3900  R15: ffff8fe41a6d1200
>     ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>  #8 [ffffb954506b3e00] ttm_resource_manager_show at ffffffffc04afde7 [ttm]
>  #9 [ffffb954506b3e30] seq_read at ffffffffb2d8f9f3
>     RIP: 00007f4c4eda8985  RSP: 00007ffdbba9e9f8  RFLAGS: 00000246
>     RAX: ffffffffffffffda  RBX: 000000000037e000  RCX: 00007f4c4eda8985
>     RDX: 000000000037e000  RSI: 00007f4c41573000  RDI: 0000000000000003
>     RBP: 000000000037e000   R8: 0000000000000000   R9: 000000000037fe30
>     R10: 0000000000000000  R11: 0000000000000246  R12: 00007f4c41573000
>     R13: 0000000000000003  R14: 00007f4c41572010  R15: 0000000000000003
>     ORIG_RAX: 0000000000000000  CS: 0033  SS: 002b
>
> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
> Fixes: af4a25bbe5e7 ("drm/vmwgfx: Add debugfs entries for various ttm resource managers")
> Cc: <stable at vger.kernel.org>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index d3e308fdfd5b..c7d90f96d16a 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -1444,12 +1444,15 @@ static void vmw_debugfs_resource_managers_init(struct vmw_private *vmw)
>                                             root, "system_ttm");
>         ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, TTM_PL_VRAM),
>                                             root, "vram_ttm");
> -       ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, VMW_PL_GMR),
> -                                           root, "gmr_ttm");
> -       ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, VMW_PL_MOB),
> -                                           root, "mob_ttm");
> -       ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, VMW_PL_SYSTEM),
> -                                           root, "system_mob_ttm");
> +       if (vmw->has_gmr)
> +               ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, VMW_PL_GMR),
> +                                                   root, "gmr_ttm");
> +       if (vmw->has_mob) {
> +               ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, VMW_PL_MOB),
> +                                                   root, "mob_ttm");
> +               ttm_resource_manager_create_debugfs(ttm_manager_type(&vmw->bdev, VMW_PL_SYSTEM),
> +                                                   root, "system_mob_ttm");
> +       }
>  }
>
>  static int vmwgfx_pm_notifier(struct notifier_block *nb, unsigned long val,
>
> base-commit: b33651a5c98dbd5a919219d8c129d0674ef74299
> --
> 2.44.0
>

Thanks! That looks great. I can push it through drm-misc-fixes.

Reviewed-by: Zack Rusin <zack.rusin at broadcom.com>

z