[Intel-gfx] [RFC PATCH 101/162] drm/i915/gtt/dg1: add PTE_LM plumbing for PPGTT

[Chris Wilson]

Quoting Matthew Auld (2020-11-27 12:06:17)
> For the PTEs we get an LM bit, to signal whether the page resides in
> SMEM or LMEM.
> 
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/gen8_ppgtt.c  | 35 ++++++++++++++++++++++-----
>  drivers/gpu/drm/i915/gt/intel_gtt.h   |  3 +++
>  drivers/gpu/drm/i915/gt/intel_ppgtt.c |  4 +++
>  3 files changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> index e2f1dfc48d43..b6fcebeef02a 100644
> --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
> @@ -5,6 +5,7 @@
>  
>  #include <linux/log2.h>
>  
> +#include "gem/i915_gem_lmem.h"
>  #include "gen8_ppgtt.h"
>  #include "i915_scatterlist.h"
>  #include "i915_trace.h"
> @@ -50,6 +51,21 @@ static u64 gen8_pte_encode(dma_addr_t addr,
>         return pte;
>  }
>  
> +static u64 gen12_pte_encode(dma_addr_t addr,
> +                           enum i915_cache_level level,
> +                           u32 flags)
> +{
> +       gen8_pte_t pte = addr | _PAGE_PRESENT | _PAGE_RW;
> +
> +       if (unlikely(flags & PTE_READ_ONLY))
> +               pte &= ~_PAGE_RW;
> +
> +       if (flags & PTE_LM)
> +               pte |= GEN12_PPGTT_PTE_LM;
> +
> +       return pte;
> +}
> +
>  static void gen8_ppgtt_notify_vgt(struct i915_ppgtt *ppgtt, bool create)
>  {
>         struct drm_i915_private *i915 = ppgtt->vm.i915;
> @@ -365,7 +381,7 @@ gen8_ppgtt_insert_pte(struct i915_ppgtt *ppgtt,
>                       u32 flags)
>  {
>         struct i915_page_directory *pd;
> -       const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level, flags);
> +       const gen8_pte_t pte_encode = ppgtt->vm.pte_encode(0, cache_level, flags);

We don't need the vfunc, since that flag will not be sent for gen8.

That bit test will be cheaper than the retpoline.
-Chris