video: tegra: nvmap: Fix build failure

Linux v6.10 and v6.11 are failing as follow_pfn was removed since kernel
v6.10 Use conftest to detect if follow_pfn, follow_pfnmap_start
functions are present or not and based upon this result, call the
appropriate functions in nvmap code.

Bug 5007238

Change-Id: Ie7e0c9bde652fd89158a5778aa8254fc86bf4696
Signed-off-by: Ketan Patil <ketanp@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3311535
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
Reviewed-by: svcacv <svcacv@nvidia.com>

drivers/video/tegra/nvmap/nvmap_alloc.c

@@ -353,7 +353,7 @@ static const unsigned int heap_policy_excl[] = {
 
 static int nvmap_page_from_vma(struct vm_area_struct *vma, ulong vaddr, struct page **page)
 {
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 12, 0)
+#if defined(NV_FOLLOW_PFNMAP_START_PRESENT)
 	unsigned long pfn;
 	struct follow_pfnmap_args args = {
 		.vma = vma,
@@ -379,7 +379,7 @@ static int nvmap_page_from_vma(struct vm_area_struct *vma, ulong vaddr, struct p
 
 fail:
 	return -EINVAL;
-#else
+#elif defined(NV_FOLLOW_PFN_PRESENT)
 	unsigned long pfn;
 
 	if (follow_pfn(vma, vaddr, &pfn)) {
@@ -398,6 +398,33 @@ fail:
 
 fail:
 	return -EINVAL;
+#else
+	unsigned long pfn;
+	spinlock_t *ptl;
+	pte_t *ptep;
+
+	mmap_read_lock(current->mm);
+	if (follow_pte(vma, vaddr, &ptep, &ptl)) {
+		pr_err("follow_pte failed\n");
+		goto fail;
+	}
+
+	pfn = pte_pfn(ptep_get(ptep));
+	if (!pfn_is_map_memory(pfn)) {
+		pr_err("no-map memory not allowed\n");
+		pte_unmap_unlock(ptep, ptl);
+		goto fail;
+	}
+
+	*page = pfn_to_page(pfn);
+	get_page(*page);
+	pte_unmap_unlock(ptep, ptl);
+	mmap_read_unlock(current->mm);
+	return 0;
+
+fail:
+	mmap_read_unlock(current->mm);
+	return -EINVAL;
 #endif
 }
 

scripts/conftest/Makefile

@@ -138,6 +138,8 @@ NV_CONFTEST_FUNCTION_COMPILE_TESTS += fd_empty
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += fd_file
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += file_struct_has_f_ref
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += folio_entire_mapcount
+NV_CONFTEST_FUNCTION_COMPILE_TESTS += follow_pfn
+NV_CONFTEST_FUNCTION_COMPILE_TESTS += follow_pfnmap_start
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += fop_unsigned_offset
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += genpd_xlate_t_has_const_of_phandle_args
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += get_file_rcu_has_double_ptr_file_arg

scripts/conftest/conftest.sh

@@ -7480,6 +7480,40 @@ compile_test() {
             compile_check_conftest "$CODE" "NV_FOLIO_ENTIRE_MAPCOUNT_PRESENT" "" "functions"
         ;;
 
+        follow_pfn)
+            #
+            # Determine if function follow_pfn() is present.
+            #
+            # Commit cb10c28ac82c9 ("mm: remove follow_pfn")
+            # remove follow_pfn() in Linux v6.10.
+            #
+            CODE="
+            #include <linux/mm.h>
+            int conftest(void)
+            {
+                return follow_pfn();
+            }"
+
+            compile_check_conftest "$CODE" "NV_FOLLOW_PFN_PRESENT" "" "functions"
+        ;;
+
+        follow_pfnmap_start)
+            #
+            # Determine if function follow_pfnmap_start() is present.
+            #
+            # Commit 6da8e9634bb7e3 ("mm: new follow_pfnmap API")
+            # add follow_pfnmap_start() in Linux v6.12.
+            #
+            CODE="
+            #include <linux/mm.h>
+            int conftest(void)
+            {
+                return follow_pfnmap_start();
+            }"
+
+            compile_check_conftest "$CODE" "NV_FOLLOW_PFNMAP_START_PRESENT" "" "functions"
+        ;;
+
         fop_unsigned_offset)
             #
             # Determine if definition FOP_UNSIGNED_OFFSET is present.