drm/i915: enforce min page size for scratch

If the device needs 64K minimum GTT pages for device local-memory,
like on XEHPSDV, then we need to fail the allocation if we can't
meet it, instead of falling back to 4K pages, otherwise we can't
safely support the insertion of device local-memory pages for
this vm, since the HW expects the correct physical alignment and
size for every PTE, if we mark the page-table as 64K GTT mode.

v2: s/userpsace/userspace [Thomas]

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211208141613.7251-5-ramalingam.c@intel.com

diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
index 1428e2b9075a2de4cb3e572d7f28d5ba27dae78d..b30e4478f09833a631a68396bf82ad6deca1aa97 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_gtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
@@ -337,6 +337,18 @@ skip:
                if (size == I915_GTT_PAGE_SIZE_4K)
                        return -ENOMEM;
 
+               /*
+                * If we need 64K minimum GTT pages for device local-memory,
+                * like on XEHPSDV, then we need to fail the allocation here,
+                * otherwise we can't safely support the insertion of
+                * local-memory pages for this vm, since the HW expects the
+                * correct physical alignment and size when the page-table is
+                * operating in 64K GTT mode, which includes any scratch PTEs,
+                * since userspace can still touch them.
+                */
+               if (HAS_64K_PAGES(vm->i915))
+                       return -ENOMEM;
+
                size = I915_GTT_PAGE_SIZE_4K;
        } while (1);
 }