[PATCH 1/2] drm/amdgpu: Unset context priority is now invalid

[Alex Deucher]

On Tue, Oct 17, 2023 at 10:27 AM Luben Tuikov <luben.tuikov at amd.com> wrote:
>
> On 2023-10-17 09:22, Alex Deucher wrote:
> > On Tue, Oct 17, 2023 at 12:52 AM Luben Tuikov <luben.tuikov at amd.com> wrote:
> >>
> >> A context priority value of AMD_CTX_PRIORITY_UNSET is now invalid--instead of
> >> carrying it around and passing it to the Direct Rendering Manager--and it
> >> becomes AMD_CTX_PRIORITY_NORMAL in amdgpu_ctx_ioctl(), the gateway to context
> >> creation.
> >>
> >> Cc: Alex Deucher <Alexander.Deucher at amd.com>
> >> Cc: Christian König <christian.koenig at amd.com>
> >> Signed-off-by: Luben Tuikov <luben.tuikov at amd.com>
> >> ---
> >>  drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> >> index 0dc9c655c4fbdb..092962b93064fc 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> >> @@ -47,7 +47,6 @@ const unsigned int amdgpu_ctx_num_entities[AMDGPU_HW_IP_NUM] = {
> >>  bool amdgpu_ctx_priority_is_valid(int32_t ctx_prio)
> >>  {
> >>         switch (ctx_prio) {
> >> -       case AMDGPU_CTX_PRIORITY_UNSET:
> >>         case AMDGPU_CTX_PRIORITY_VERY_LOW:
> >>         case AMDGPU_CTX_PRIORITY_LOW:
> >>         case AMDGPU_CTX_PRIORITY_NORMAL:
> >> @@ -55,6 +54,7 @@ bool amdgpu_ctx_priority_is_valid(int32_t ctx_prio)
> >>         case AMDGPU_CTX_PRIORITY_VERY_HIGH:
> >>                 return true;
> >>         default:
> >> +       case AMDGPU_CTX_PRIORITY_UNSET:
> >>                 return false;
> >
> > I  don't recall if any userspace uses this, but this would break
> > userspace if it does.
>
> This is shielded from user space in the following manner,
> 1) amdgpu_ctx_priority_is_valid() is called from amdgpu_ctx_ioctl() and
>    if amdgpu_ctx_priority_is_valid() returns false, we set the priority to NORMAL.
>    See the 2nd patch.

Ah, I see.  Thanks.  Series is:
Acked-by: Alex Deucher <alexander.deucher at amd.com>


> 2) It is also called from amdgpu_ctx_priority_permit(), which is called
>    from amdgpu_ctx_init() which is called from amdgpu_ctx_alloc() which
>    is called from amdgpu_ctx_ioctl(), _after_ the call described above,
>    and thus priority is now NORMAL.
>
> Plus I'm typing this on a running system with 6.6.0 + those two patches.
>
> User space can send us down UNSET, but we set it to NORMAL.
>
> Can I get an R-B?
>
> >
> > Alex
> >
> >>         }
> >>  }
> >>
> >> base-commit: dc9b2e683bcba017588b9aaad80f442ad004a48f
> >> --
> >> 2.42.0
> >>
>
> --
> Regards,
> Luben
>