Quoting Lionel Landwerlin (2018-06-01 10:52:14)
> We currently using GuC as a proxy to the hardware. When Guc is used in
> such mode, it consumes the bit 20 of the hw_id to indicate that the
> workload was submitted by proxy.
>
> So far we probably haven't seen the issue because we need to allocate
> 1048576+ contexts to hit this issue. Still, we should avoid allocating
> the hw_id on that bit and restriction to bits [0:19] (i.e 20bits
> instead of 21).
>
> v2: Leave the max hw_id computation in i915_gem_context.c (Michel)
>
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
> BSpec: 1237
> ---
> drivers/gpu/drm/i915/i915_drv.h | 1 +
> drivers/gpu/drm/i915/i915_gem_context.c | 14 +++++++++++---
> drivers/gpu/drm/i915/intel_lrc.c | 2 +-
> 3 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 38157df6ff5c..7088a1c3b6ad 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1841,6 +1841,7 @@ struct drm_i915_private {
> */
> struct ida hw_ida;
> #define MAX_CONTEXT_HW_ID (1<<21) /* exclusive */
> +#define MAX_GUC_CONTEXT_HW_ID (1<<20) /* exclusive */
> #define GEN11_MAX_CONTEXT_HW_ID (1<<11) /* exclusive */
> } contexts;
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 81f086397d10..fa732592e221 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -208,10 +208,18 @@ static int assign_hw_id(struct drm_i915_private *dev_priv, unsigned *out)
> int ret;
> unsigned int max;
>
> - if (INTEL_GEN(dev_priv) >= 11)
> + if (INTEL_GEN(dev_priv) >= 11) {
> max = GEN11_MAX_CONTEXT_HW_ID;
> - else
> - max = MAX_CONTEXT_HW_ID;
> + } else {
> + /*
> + * When using GuC in proxy submission, GuC consumes the
> + * highest bit in the context id to indicate proxy submission.
> + */
> + max = USES_GUC_SUBMISSION(dev_priv) ?
> + MAX_GUC_CONTEXT_HW_ID :
> + MAX_CONTEXT_HW_ID;
I'm just going to say mixing if() and ternary ?: isn't great style.
Acked-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris
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