diff options
| author | Chris Wilson <chris@chris-wilson.co.uk> | 2022-12-01 21:39:12 +0100 |
|---|---|---|
| committer | Andi Shyti <andi.shyti@linux.intel.com> | 2022-12-06 10:52:45 +0100 |
| commit | 6110225144d1136db5b026a22efbd76cee197027 (patch) | |
| tree | ad0977fa473be3036839bd6f8c5ddde02849180c /drivers/gpu/drm/i915/i915_gem_gtt.h | |
| parent | 8e4ee5e87ce60be439eca8d3a65bd870f6821902 (diff) | |
drm/i915: Introduce guard pages to i915_vma
Introduce the concept of padding the i915_vma with guard pages before
and after. The major consequence is that all ordinary uses of i915_vma
must use i915_vma_offset/i915_vma_size and not i915_vma.node.start/size
directly, as the drm_mm_node will include the guard pages that surround
our object.
The biggest connundrum is how exactly to mix requesting a fixed address
with guard pages, particularly through the existing uABI. The user does
not know about guard pages, so such must be transparent to the user, and
so the execobj.offset must be that of the object itself excluding the
guard. So a PIN_OFFSET_FIXED must then be exclusive of the guard pages.
The caveat is that some placements will be impossible with guard pages,
as wrap arounds need to be avoided, and the vma itself will require a
larger node. We must not report EINVAL but ENOSPC as these are unavailable
locations within the GTT rather than conflicting user requirements.
In the next patch, we start using guard pages for scanout objects. While
these are limited to GGTT vma, on a few platforms these vma (or at least
an alias of the vma) is shared with userspace, so we may leak the
existence of such guards if we are not careful to ensure that the
execobj.offset is transparent and excludes the guards. (On such platforms
like ivb, without full-ppgtt, userspace has to use relocations so the
presence of more untouchable regions within its GTT such be of no further
issue.)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221201203912.346110-1-andi.shyti@linux.intel.com
Diffstat (limited to 'drivers/gpu/drm/i915/i915_gem_gtt.h')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem_gtt.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h index 8c2f57eb5dda..243419783052 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.h +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h @@ -44,7 +44,8 @@ int i915_gem_gtt_insert(struct i915_address_space *vm, #define PIN_HIGH BIT_ULL(5) #define PIN_OFFSET_BIAS BIT_ULL(6) #define PIN_OFFSET_FIXED BIT_ULL(7) -#define PIN_VALIDATE BIT_ULL(8) /* validate placement only, no need to call unpin() */ +#define PIN_OFFSET_GUARD BIT_ULL(8) +#define PIN_VALIDATE BIT_ULL(9) /* validate placement only, no need to call unpin() */ #define PIN_GLOBAL BIT_ULL(10) /* I915_VMA_GLOBAL_BIND */ #define PIN_USER BIT_ULL(11) /* I915_VMA_LOCAL_BIND */ |