[RFC PATCH 43/97] drm/i915/guc: Add lrc descriptor context lookup array

[Daniel Vetter]

On Thu, May 06, 2021 at 12:13:57PM -0700, Matthew Brost wrote:
> Add lrc descriptor context lookup array which can resolve the
> intel_context from the lrc descriptor index. In addition to lookup, it
> can determine in the lrc descriptor context is currently registered with
> the GuC by checking if an entry for a descriptor index is present.
> Future patches in the series will make use of this array.
> 
> Cc: John Harrison <john.c.harrison at intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/uc/intel_guc.h        |  5 +++
>  .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 32 +++++++++++++++++--
>  2 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> index d84f37afb9d8..2eb6c497e43c 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> @@ -6,6 +6,8 @@
>  #ifndef _INTEL_GUC_H_
>  #define _INTEL_GUC_H_
>  
> +#include "linux/xarray.h"
> +
>  #include "intel_uncore.h"
>  #include "intel_guc_fw.h"
>  #include "intel_guc_fwif.h"
> @@ -47,6 +49,9 @@ struct intel_guc {
>  	struct i915_vma *lrc_desc_pool;
>  	void *lrc_desc_pool_vaddr;
>  
> +	/* guc_id to intel_context lookup */
> +	struct xarray context_lookup;

The current code sets a disastrous example, but for stuff like this it's
always good to explain the locking, and who's holding references and how
you're handling cycles. Since I guess the intel_context also holds the
guc_id alive somehow.

Again holds for the entire series, where it makes sense (as in we don't
expect to rewrite the entire code anyway).
-Daniel

> +
>  	/* Control params for fw initialization */
>  	u32 params[GUC_CTL_MAX_DWORDS];
>  
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 6acc1ef34f92..c2b6d27404b7 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -65,8 +65,6 @@ static inline struct i915_priolist *to_priolist(struct rb_node *rb)
>  	return rb_entry(rb, struct i915_priolist, node);
>  }
>  
> -/* Future patches will use this function */
> -__attribute__ ((unused))
>  static struct guc_lrc_desc *__get_lrc_desc(struct intel_guc *guc, u32 index)
>  {
>  	struct guc_lrc_desc *base = guc->lrc_desc_pool_vaddr;
> @@ -76,6 +74,15 @@ static struct guc_lrc_desc *__get_lrc_desc(struct intel_guc *guc, u32 index)
>  	return &base[index];
>  }
>  
> +static inline struct intel_context *__get_context(struct intel_guc *guc, u32 id)
> +{
> +	struct intel_context *ce = xa_load(&guc->context_lookup, id);
> +
> +	GEM_BUG_ON(id >= GUC_MAX_LRC_DESCRIPTORS);
> +
> +	return ce;
> +}
> +
>  static int guc_lrc_desc_pool_create(struct intel_guc *guc)
>  {
>  	u32 size;
> @@ -96,6 +103,25 @@ static void guc_lrc_desc_pool_destroy(struct intel_guc *guc)
>  	i915_vma_unpin_and_release(&guc->lrc_desc_pool, I915_VMA_RELEASE_MAP);
>  }
>  
> +static inline void reset_lrc_desc(struct intel_guc *guc, u32 id)
> +{
> +	struct guc_lrc_desc *desc = __get_lrc_desc(guc, id);
> +
> +	memset(desc, 0, sizeof(*desc));
> +	xa_erase_irq(&guc->context_lookup, id);
> +}
> +
> +static inline bool lrc_desc_registered(struct intel_guc *guc, u32 id)
> +{
> +	return __get_context(guc, id);
> +}
> +
> +static inline void set_lrc_desc_registered(struct intel_guc *guc, u32 id,
> +					   struct intel_context *ce)
> +{
> +	xa_store_irq(&guc->context_lookup, id, ce, GFP_ATOMIC);
> +}
> +
>  static void guc_add_request(struct intel_guc *guc, struct i915_request *rq)
>  {
>  	/* Leaving stub as this function will be used in future patches */
> @@ -404,6 +430,8 @@ int intel_guc_submission_init(struct intel_guc *guc)
>  	 */
>  	GEM_BUG_ON(!guc->lrc_desc_pool);
>  
> +	xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ);
> +
>  	return 0;
>  }
>  
> -- 
> 2.28.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch