Patch "drm/i915: Move the release of PT page to the upper caller" has been added to the 4.10-stable tree

Patch "drm/i915: Move the release of PT page to the upper caller" has been added to the 4.10-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 4.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-i915-move-the-release-of-pt-page-to-the-upper-caller.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From a18dbba8f01ffae229d00517994f84e7bfad4c49 Mon Sep 17 00:00:00 2001
From: Zhi Wang <zhi.a.wang@intel.com>
Date: Tue, 29 Nov 2016 14:55:16 +0800
Subject: drm/i915: Move the release of PT page to the upper caller
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Zhi Wang <zhi.a.wang@intel.com>

commit a18dbba8f01ffae229d00517994f84e7bfad4c49 upstream.

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.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michał Winiarski <michal.winiarski@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>
Link: https://patchwork.freedesktop.org/patch/122697/msgid/1479728666-25333-1-git-send-email-zhi.a.wang@intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1480402516-22275-1-git-send-email-zhi.a.wang@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/i915_gem_gtt.c |   18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

--- 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 i
 
 	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 i
 			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;
 }
@@ -795,7 +792,6 @@ static bool gen8_ppgtt_clear_pdp(struct
 				 uint64_t length)
 {
 	struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
-	struct drm_i915_private *dev_priv = to_i915(vm->dev);
 	struct i915_page_directory *pd;
 	uint64_t pdpe;
 	gen8_ppgtt_pdpe_t *pdpe_vaddr;
@@ -813,16 +809,14 @@ static bool gen8_ppgtt_clear_pdp(struct
 				pdpe_vaddr[pdpe] = scratch_pdpe;
 				kunmap_px(ppgtt, pdpe_vaddr);
 			}
+			free_pd(to_i915(vm->dev), 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;
 }
@@ -836,6 +830,7 @@ static void gen8_ppgtt_clear_pml4(struct
 				  uint64_t start,
 				  uint64_t length)
 {
+	struct drm_i915_private *dev_priv = to_i915(vm->dev);
 	struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
 	struct i915_page_directory_pointer *pdp;
 	uint64_t pml4e;
@@ -854,6 +849,7 @@ static void gen8_ppgtt_clear_pml4(struct
 			pml4e_vaddr = kmap_px(pml4);
 			pml4e_vaddr[pml4e] = scratch_pml4e;
 			kunmap_px(ppgtt, pml4e_vaddr);
+			free_pdp(dev_priv, pdp);
 		}
 	}
 }


Patches currently in stable-queue which might be from zhi.a.wang@intel.com are

queue-4.10/drm-i915-let-execlist_update_context-cover-full_ppgtt-mode.patch
queue-4.10/drm-i915-move-the-release-of-pt-page-to-the-upper-caller.patch
queue-4.10/drm-i915-kvmgt-hold-struct-kvm-reference.patch
queue-4.10/drm-i915-a-hotfix-for-making-aliasing-ppgtt-work-for-gvt-g.patch