[PATCH v4 3/4] drm/xe: Assert that VF will never use fixed placement of BOs

[Tomasz Lis <tomasz.lis@intel.com>]

Most BOs do not care at which offset they will be accessed within
GGTT or PPGTT. The few which do care, should be only created
on PF, and mapped within GGTT. On VFs, mapping at fixed offset
would be problematic, as each VF is granted access to a range of
GGTT address space.

So, since fixed addresses of GGTT mapping can only be used on PF,
we can add an assert which makes sure no attempt of fixed placement
will happen for a driver probed on a VF.

The assert will also ensure that VF migration can be properly
performed without a need for special handling of the fixed placement
addresses.

Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
---
 drivers/gpu/drm/xe/xe_bo.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 7b6502081873..8e826a4aa574 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -2259,6 +2259,12 @@ static int __xe_bo_fixed_placement(struct xe_device *xe,
 	struct ttm_place *place = bo->placements;
 	u32 vram_flag, vram_stolen_flags;
 
+	/*
+	 * to allow fixed placement in GGTT of a VF, post-migration fixups
+	 * would have to include shifting the page ranges
+	 */
+	xe_assert(xe, !IS_SRIOV_VF(xe) || !(bo->flags & XE_BO_FLAG_GGTT));
+
 	if (flags & (XE_BO_FLAG_USER | XE_BO_FLAG_SYSTEM))
 		return -EINVAL;
 
-- 
2.25.1