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@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Cc: Michel Thierry <michel.thierry@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
Cc: Zhiyuan Lv <zhiyuan.lv@xxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> #v4.10+
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Zhi Wang <zhi.a.wang@xxxxxxxxx>
Link:
https://patchwork.freedesktop.org/patch/122697/msgid/1479728666-25333-1-git-send-email-zhi.a.wang@xxxxxxxxx
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Link:
http://patchwork.freedesktop.org/patch/msgid/1480402516-22275-1-git-send-email-zhi.a.wang@xxxxxxxxx
---
drivers/gpu/drm/i915/i915_gem_gtt.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c
b/drivers/gpu/drm/i915/i915_gem_gtt.c
index b4bde14..6cee707 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;
}
@@ -795,7 +792,6 @@ static bool gen8_ppgtt_clear_pdp(struct
i915_address_space *vm,
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
i915_address_space *vm,
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
i915_address_space *vm,
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
i915_address_space *vm,
pml4e_vaddr = kmap_px(pml4);
pml4e_vaddr[pml4e] = scratch_pml4e;
kunmap_px(ppgtt, pml4e_vaddr);
+ free_pdp(dev_priv, pdp);
}
}
}