linux-6.1.76, 6.6.15, and 6.7.3 have modified the non-ARCH-specific
pfn_valid() to use __rcu_read_lock/unlock[1] that is marked GPL and
cannot be used here[2][3][4] unless use the open source variant.

As a workaround, reuse the old implementation until NVIDIA makes
a fixed release (due to no longer be using pfn_valid[5], likely
with its own implementation similarly to this patch).

Safe to use with kernel >=5.15 or so but older ones had a different
pfn_valid implementation. However 5.15 and older branches are
"currently" not affected, so simply limit to >=6.1.76.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/include/linux/mmzone.h?h=v6.7.3&id=3a01daace71b521563c38bbbf874e14c3e58adb7
[2] https://bugs.gentoo.org/923456
[3] https://forums.developer.nvidia.com/t/280908
[4] https://github.com/NVIDIA/open-gpu-kernel-modules/issues/594
[5] https://github.com/NVIDIA/open-gpu-kernel-modules/issues/594#issuecomment-1916197641
--- a/kernel/common/inc/nv-linux.h
+++ b/kernel/common/inc/nv-linux.h
@@ -1990,2 +1990,23 @@
 
+#if defined(CONFIG_HAVE_ARCH_PFN_VALID) || LINUX_VERSION_CODE < KERNEL_VERSION(6,1,76)
+#  define nv_pfn_valid pfn_valid
+#else
+/* pre-6.1.76 kernel pfn_valid version without GPL rcu_read_lock/unlock() */
+static inline int nv_pfn_valid(unsigned long pfn)
+{
+        struct mem_section *ms;
+
+        if (PHYS_PFN(PFN_PHYS(pfn)) != pfn)
+                return 0;
+
+        if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
+                return 0;
+
+        ms = __pfn_to_section(pfn);
+        if (!valid_section(ms))
+                return 0;
+
+        return early_section(ms) || pfn_section_valid(ms, pfn);
+}
+#endif
 #endif  /* _NV_LINUX_H_ */
--- a/kernel/nvidia/nv-mmap.c
+++ b/kernel/nvidia/nv-mmap.c
@@ -576,3 +576,3 @@
             if (!IS_REG_OFFSET(nv, access_start, access_len) &&
-                (pfn_valid(PFN_DOWN(mmap_start))))
+                (nv_pfn_valid(PFN_DOWN(mmap_start))))
             {
--- a/kernel/nvidia/os-mlock.c
+++ b/kernel/nvidia/os-mlock.c
@@ -102,3 +102,3 @@
         if ((nv_follow_pfn(vma, (start + (i * PAGE_SIZE)), &pfn) < 0) ||
-            (!pfn_valid(pfn)))
+            (!nv_pfn_valid(pfn)))
         {
@@ -176,3 +176,3 @@
 
-    if (pfn_valid(pfn))
+    if (nv_pfn_valid(pfn))
     {