[PATCH] drm/gpusvm: Reject VMAs with VM_IO or VM_PFNMAP when creating SVM ranges

[Matthew Brost <matthew.brost@intel.com>]

VMAs marked with VM_IO or VM_PFNMAP are not backed by struct page
objects, which GPUSVM requires in order to operate correctly. In
particular, get_pages() relies on hmm_range_fault() to resolve struct
pages for the target range.

Attempting to create an SVM range on such VMAs results in repeated
get_pages() failures and can lead to an infinite loop inside a driver’s
page‑fault handler. Prevent this by rejecting ranges on VM_IO or
VM_PFNMAP VMAs and returning -EIO.

Fixes: 99624bdff867 ("drm/gpusvm: Add support for GPU Shared Virtual Memory")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/drm_gpusvm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 4b928fda5b12..7993e85c0566 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -1065,6 +1065,11 @@ drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm,
 		goto err_notifier_remove;
 	}
 
+	if (vas->vm_flags & (VM_IO | VM_PFNMAP)) {
+		err = -EIO;
+		goto err_notifier_remove;
+	}
+
 	range = drm_gpusvm_range_find(notifier, fault_addr, fault_addr + 1);
 	if (range)
 		goto out_mmunlock;
-- 
2.34.1