Re: [PATCH] drm/xe: Allow to exclude part of GGTT from allocations

["Piotr Piórkowski" <piotr.piorkowski@intel.com>]

Michal Wajdeczko <michal.wajdeczko@intel.com> wrote on czw [2024-sty-11 19:25:59 +0100]:
> Soon we will be required to exclude some of the GGTT addresses
> from the allocations, since on some platforms running the SR-IOV VF
> mode, we will be able to use only selected range of the GGTT space.
> 
> Add helper functions to manage such GGTT range exclusions, and
> follow the naming from the similar concept used by GVT-g.
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_ggtt.c | 71 ++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_ggtt.h |  3 ++
>  2 files changed, 74 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
> index c639dbf3bdd2..6fdf830678b3 100644
> --- a/drivers/gpu/drm/xe/xe_ggtt.c
> +++ b/drivers/gpu/drm/xe/xe_ggtt.c
> @@ -11,9 +11,12 @@
>  #include <drm/i915_drm.h>
>  
>  #include "regs/xe_gt_regs.h"
> +#include "regs/xe_regs.h"
> +#include "xe_assert.h"
>  #include "xe_bo.h"
>  #include "xe_device.h"
>  #include "xe_gt.h"
> +#include "xe_gt_printk.h"
>  #include "xe_gt_tlb_invalidation.h"
>  #include "xe_map.h"
>  #include "xe_mmio.h"
> @@ -312,6 +315,74 @@ void xe_ggtt_printk(struct xe_ggtt *ggtt, const char *prefix)
>  	}
>  }
>  
> +static void xe_ggtt_dump_node(struct xe_ggtt *ggtt,
> +			      const struct drm_mm_node *node, const char *description)
> +{
> +	char buf[10];
> +
> +	if (IS_ENABLED(CONFIG_DRM_XE_DEBUG)) {
> +		string_get_size(node->size, 1, STRING_UNITS_2, buf, sizeof(buf));
> +		xe_gt_dbg(ggtt->tile->primary_gt, "GGTT %#llx-%#llx (%s) %s\n",
> +			  node->start, node->start + node->size, buf, description);
My personal preference in the log is for the address range to be 0x1000 - 0x1fff rather
than 0x1000 - 0x2000.

> +	}
> +}
> +
> +/**
> + * xe_ggtt_balloon - prevent allocation of specified GGTT addresses
> + * @ggtt: the &xe_ggtt where we want to make reservation
> + * @start: the starting GGTT address of the reserved region
> + * @end: then end GGTT address of the reserved region
> + * @node: the &drm_mm_node to hold reserved GGTT node
> + *
> + * Use xe_ggtt_deballoon() to release a reserved GGTT node.
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int xe_ggtt_balloon(struct xe_ggtt *ggtt, u64 start, u64 end, struct drm_mm_node *node)
> +{
> +	int err;
> +
> +	xe_tile_assert(ggtt->tile, start < end);
> +	xe_tile_assert(ggtt->tile, IS_ALIGNED(start, XE_PAGE_SIZE));
> +	xe_tile_assert(ggtt->tile, IS_ALIGNED(end, XE_PAGE_SIZE));
> +	xe_tile_assert(ggtt->tile, !drm_mm_node_allocated(node));
> +
> +	node->color = 0;
> +	node->start = start;
> +	node->size = end - start;
> +
> +	mutex_lock(&ggtt->lock);
> +	err = drm_mm_reserve_node(&ggtt->mm, node);
> +	mutex_unlock(&ggtt->lock);
> +
> +	if (xe_gt_WARN(ggtt->tile->primary_gt, err,
> +		       "Failed to balloon GGTT %#llx-%#llx (%pe)\n",
> +		       node->start, node->start + node->size, ERR_PTR(err)))
> +		return err;
> +
> +	xe_ggtt_dump_node(ggtt, node, "balloon");
> +	return 0;
> +}
> +
> +/**
> + * xe_ggtt_deballoon - release a reserved GGTT region
> + * @ggtt: the &xe_ggtt where reserved node belongs
> + * @node: the &drm_mm_node with reserved GGTT region
> + *
> + * See xe_ggtt_balloon() for details.
> + */
> +void xe_ggtt_deballoon(struct xe_ggtt *ggtt, struct drm_mm_node *node)
> +{
> +	if (!drm_mm_node_allocated(node))
> +		return;
> +
> +	xe_ggtt_dump_node(ggtt, node, "deballoon");
> +
> +	mutex_lock(&ggtt->lock);
> +	drm_mm_remove_node(node);
> +	mutex_unlock(&ggtt->lock);
> +}
> +

Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>

>  int xe_ggtt_insert_special_node_locked(struct xe_ggtt *ggtt, struct drm_mm_node *node,
>  				       u32 size, u32 align, u32 mm_flags)
>  {
> diff --git a/drivers/gpu/drm/xe/xe_ggtt.h b/drivers/gpu/drm/xe/xe_ggtt.h
> index a09c166dff70..42705e1338e1 100644
> --- a/drivers/gpu/drm/xe/xe_ggtt.h
> +++ b/drivers/gpu/drm/xe/xe_ggtt.h
> @@ -16,6 +16,9 @@ int xe_ggtt_init_early(struct xe_ggtt *ggtt);
>  int xe_ggtt_init(struct xe_ggtt *ggtt);
>  void xe_ggtt_printk(struct xe_ggtt *ggtt, const char *prefix);
>  
> +int xe_ggtt_balloon(struct xe_ggtt *ggtt, u64 start, u64 size, struct drm_mm_node *node);
> +void xe_ggtt_deballoon(struct xe_ggtt *ggtt, struct drm_mm_node *node);
> +
>  int xe_ggtt_insert_special_node(struct xe_ggtt *ggtt, struct drm_mm_node *node,
>  				u32 size, u32 align);
>  int xe_ggtt_insert_special_node_locked(struct xe_ggtt *ggtt,
> 
> base-commit: 79184e72263e91528195db01783148435c7e4fad
> -- 
> 2.25.1
> 

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