nvidia: use vzalloc for oversized page table allocations

nvos_create_alloc() allocates at->page_table as a single array of
nvidia_pte_t entries:

    pt_size = num_pages * sizeof(nvidia_pte_t)

For very large registered system-memory ranges, pt_size can exceed
INT_MAX. For example, a 512 GiB range with 4 KiB base pages requires
134,217,728 entries. With 16-byte nvidia_pte_t entries, pt_size is
2,147,483,648 bytes.

kvzalloc() rejects sizes larger than INT_MAX before falling back to
vmalloc, so nvos_create_alloc() can fail even though the page table is
CPU-side metadata and does not require physical contiguity.

Use vzalloc() directly when pt_size exceeds INT_MAX, while preserving
the existing kvzalloc() path for smaller allocations.

The existing kvfree() release path remains valid for both kvzalloc()
and vzalloc() allocations.

Signed-off-by: Guzebing <guzebing1612@gmail.com>

Author: guzebing1612-dev

kernel-open/nvidia/nv.c

@@ -411,7 +411,15 @@ nv_alloc_t *nvos_create_alloc(
         return NULL;
     }
 
-    at->page_table = kvzalloc(pt_size, NV_GFP_KERNEL);
+    /*
+     * kvmalloc()/kvzalloc() reject sizes larger than INT_MAX before
+     * falling back to vmalloc. Large registered system-memory ranges can
+     * require a page table larger than that, so use vzalloc() directly.
+     */
+    if (pt_size > (NvU64)INT_MAX)
+	at->page_table = vzalloc(pt_size);
+    else
+	at->page_table = kvzalloc(pt_size, NV_GFP_KERNEL);
     if (at->page_table == NULL)
     {
         nv_printf(NV_DBG_ERRORS, "NVRM: failed to allocate page table\n");