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[v2] drm/i915: Move the release of PT page to the upper caller

Message ID 1480472243-26256-1-git-send-email-zhi.a.wang@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Wang, Zhi A Nov. 30, 2016, 2:17 a.m. UTC 
a PT page will be released if it doesn't contain any meaningful mappings
during PPGTT page table shrinking. The PT entry in the upper level will
be set to a scratch entry.

Normally this works nicely, but in virtualization world, the PPGTT page
table is tracked by hypervisor. Releasing the PT page before modifying
the upper level PT entry would cause extra efforts.

As the tracked page has been returned to OS before losing track from
hypervisor, it could be written in any pattern. Hypervisor has to recognize
if a page is still being used as a PT page by validating these writing
patterns. It's complicated. Better let the guest modify the PT entry in
upper level PT first, then release the PT page.

v2:

Tvrtko:
- Reuse struct drm_i915_private * as much as possible in functions.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> v1
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com> v1
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhiyuan Lv <zhiyuan.lv@intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index b4bde14..e788d22 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -736,10 +736,8 @@  static bool gen8_ppgtt_clear_pt(struct i915_address_space *vm,
 
 	bitmap_clear(pt->used_ptes, pte, num_entries);
 
-	if (bitmap_empty(pt->used_ptes, GEN8_PTES)) {
-		free_pt(to_i915(vm->dev), pt);
+	if (bitmap_empty(pt->used_ptes, GEN8_PTES))
 		return true;
-	}
 
 	pt_vaddr = kmap_px(pt);
 
@@ -775,13 +773,12 @@  static bool gen8_ppgtt_clear_pd(struct i915_address_space *vm,
 			pde_vaddr = kmap_px(pd);
 			pde_vaddr[pde] = scratch_pde;
 			kunmap_px(ppgtt, pde_vaddr);
+			free_pt(to_i915(vm->dev), pt);
 		}
 	}
 
-	if (bitmap_empty(pd->used_pdes, I915_PDES)) {
-		free_pd(to_i915(vm->dev), pd);
+	if (bitmap_empty(pd->used_pdes, I915_PDES))
 		return true;
-	}
 
 	return false;
 }
@@ -813,16 +810,14 @@  static bool gen8_ppgtt_clear_pdp(struct i915_address_space *vm,
 				pdpe_vaddr[pdpe] = scratch_pdpe;
 				kunmap_px(ppgtt, pdpe_vaddr);
 			}
+			free_pd(dev_priv, pd);
 		}
 	}
 
 	mark_tlbs_dirty(ppgtt);
 
-	if (USES_FULL_48BIT_PPGTT(dev_priv) &&
-	    bitmap_empty(pdp->used_pdpes, I915_PDPES_PER_PDP(dev_priv))) {
-		free_pdp(dev_priv, pdp);
+	if (bitmap_empty(pdp->used_pdpes, I915_PDPES_PER_PDP(dev_priv)))
 		return true;
-	}
 
 	return false;
 }
@@ -854,6 +849,7 @@  static void gen8_ppgtt_clear_pml4(struct i915_address_space *vm,
 			pml4e_vaddr = kmap_px(pml4);
 			pml4e_vaddr[pml4e] = scratch_pml4e;
 			kunmap_px(ppgtt, pml4e_vaddr);
+			free_pdp(to_i915(vm->dev), pdp);
 		}
 	}
 }