Enable these tests to be run on other pfnmap'ed memory like
NVIDIA's EGM.

Add '--' as a separator to pass in file path. This allows
passing of cmd line arguments to kselftest_harness.
Use '/dev/mem' as default filename.

Existing test passes:
	pfnmap
	TAP version 13
	1..6
	# Starting 6 tests from 1 test cases.
	# PASSED: 6 / 6 tests passed.
	# Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0

Pass params to kselftest_harness:
	pfnmap -r pfnmap:mremap_fixed
	TAP version 13
	1..1
	# Starting 1 tests from 1 test cases.
	#  RUN           pfnmap.mremap_fixed ...
	#            OK  pfnmap.mremap_fixed
	ok 1 pfnmap.mremap_fixed
	# PASSED: 1 / 1 tests passed.
	# Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

Pass random file name as input:
	pfnmap -- /dev/blah
	TAP version 13
	1..6
	# Starting 6 tests from 1 test cases.
	#  RUN           pfnmap.madvise_disallowed ...
	#      SKIP      Cannot open '/dev/blah'

Signed-off-by: Sudarsan Mahendran <sudarsanm@google.com>
---
 tools/testing/selftests/mm/pfnmap.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c
index 866ac023baf5..2d4e8b165f91 100644
--- a/tools/testing/selftests/mm/pfnmap.c
+++ b/tools/testing/selftests/mm/pfnmap.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Basic VM_PFNMAP tests relying on mmap() of '/dev/mem'
+ * Basic VM_PFNMAP tests relying on mmap() of input file provided.
+ * Use '/dev/mem' as default.
  *
  * Copyright 2025, Red Hat, Inc.
  *
@@ -25,6 +26,7 @@
 #include "vm_util.h"
 
 static sigjmp_buf sigjmp_buf_env;
+static char *file = "/dev/mem";
 
 static void signal_handler(int sig)
 {
@@ -117,19 +119,19 @@ FIXTURE_SETUP(pfnmap)
 	if (find_ram_target(&self->phys_addr, self->pagesize))
 		SKIP(return, "Cannot find ram target in '/proc/iomem'\n");
 
-	self->dev_mem_fd = open("/dev/mem", O_RDONLY);
+	self->dev_mem_fd = open(file, O_RDONLY);
 	if (self->dev_mem_fd < 0)
-		SKIP(return, "Cannot open '/dev/mem'\n");
+		SKIP(return, "Cannot open '%s'\n", file);
 
 	self->size1 = self->pagesize * 2;
 	self->addr1 = mmap(NULL, self->size1, PROT_READ, MAP_SHARED,
 			   self->dev_mem_fd, self->phys_addr);
 	if (self->addr1 == MAP_FAILED)
-		SKIP(return, "Cannot mmap '/dev/mem'\n");
+		SKIP(return, "Cannot mmap '%s'\n", file);
 
 	/* ... and want to be able to read from them. */
 	if (test_read_access(self->addr1, self->size1, self->pagesize))
-		SKIP(return, "Cannot read-access mmap'ed '/dev/mem'\n");
+		SKIP(return, "Cannot read-access mmap'ed '%s'\n", file);
 
 	self->size2 = 0;
 	self->addr2 = MAP_FAILED;
@@ -246,4 +248,14 @@ TEST_F(pfnmap, fork)
 	ASSERT_EQ(ret, 0);
 }
 
-TEST_HARNESS_MAIN
+int main(int argc, char **argv)
+{
+	for (int i = 1; i < argc; i++) {
+		if (strcmp(argv[i], "--") == 0) {
+			if (i + 1 < argc && strlen(argv[i + 1]) > 0)
+				file = argv[i + 1];
+			return test_harness_run(i, argv);
+		}
+	}
+	return test_harness_run(argc, argv);
+}
-- 
2.50.1.565.gc32cd1483b-goog

On 31.07.25 22:10, Sudarsan Mahendran wrote:
> Enable these tests to be run on other pfnmap'ed memory like
> NVIDIA's EGM.
> 
> Add '--' as a separator to pass in file path. This allows
> passing of cmd line arguments to kselftest_harness.
> Use '/dev/mem' as default filename.
> 
> Existing test passes:
> 	pfnmap
> 	TAP version 13
> 	1..6
> 	# Starting 6 tests from 1 test cases.
> 	# PASSED: 6 / 6 tests passed.
> 	# Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
> Pass params to kselftest_harness:
> 	pfnmap -r pfnmap:mremap_fixed
> 	TAP version 13
> 	1..1
> 	# Starting 1 tests from 1 test cases.
> 	#  RUN           pfnmap.mremap_fixed ...
> 	#            OK  pfnmap.mremap_fixed
> 	ok 1 pfnmap.mremap_fixed
> 	# PASSED: 1 / 1 tests passed.
> 	# Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
> Pass random file name as input:
> 	pfnmap -- /dev/blah
> 	TAP version 13
> 	1..6
> 	# Starting 6 tests from 1 test cases.
> 	#  RUN           pfnmap.madvise_disallowed ...
> 	#      SKIP      Cannot open '/dev/blah'

Now, if you really just pass a random *actual file* that exists, the 
test case will not actually test what we want.

Unless you have a way to verify that you actually get a PFNMAP mapping, 
this extension is questionable. It will make the test report possibly 
wrong results when wrong files are provided.

I think we can test whether we get a PFNMAP mapping by looking at the 
flags in smaps output ("pf" in flags), so I would expect such a test to 
be done in pfnmap, and the test should FAIL if the file would not create 
a PFNMAP.


But more importantly, we rely on "/proc/iomem" to find a RAM target in 
/dev/mem. That doesn't make any sense with what you are doing here.

If we are not provided /dev/mem, you should probably try mapping offset 
0 of the file.

-- 
Cheers,

David / dhildenb

Thanks for the review!
I've sent a follow up v2 patch.


On Fri, Aug 1, 2025 at 12:15 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 31.07.25 22:10, Sudarsan Mahendran wrote:
> > Enable these tests to be run on other pfnmap'ed memory like
> > NVIDIA's EGM.
> >
> > Add '--' as a separator to pass in file path. This allows
> > passing of cmd line arguments to kselftest_harness.
> > Use '/dev/mem' as default filename.
> >
> > Existing test passes:
> >       pfnmap
> >       TAP version 13
> >       1..6
> >       # Starting 6 tests from 1 test cases.
> >       # PASSED: 6 / 6 tests passed.
> >       # Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0
> >
> > Pass params to kselftest_harness:
> >       pfnmap -r pfnmap:mremap_fixed
> >       TAP version 13
> >       1..1
> >       # Starting 1 tests from 1 test cases.
> >       #  RUN           pfnmap.mremap_fixed ...
> >       #            OK  pfnmap.mremap_fixed
> >       ok 1 pfnmap.mremap_fixed
> >       # PASSED: 1 / 1 tests passed.
> >       # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
> >
> > Pass random file name as input:
> >       pfnmap -- /dev/blah
> >       TAP version 13
> >       1..6
> >       # Starting 6 tests from 1 test cases.
> >       #  RUN           pfnmap.madvise_disallowed ...
> >       #      SKIP      Cannot open '/dev/blah'
>
> Now, if you really just pass a random *actual file* that exists, the
> test case will not actually test what we want.
>
> Unless you have a way to verify that you actually get a PFNMAP mapping,
> this extension is questionable. It will make the test report possibly
> wrong results when wrong files are provided.
>
> I think we can test whether we get a PFNMAP mapping by looking at the
> flags in smaps output ("pf" in flags), so I would expect such a test to
> be done in pfnmap, and the test should FAIL if the file would not create
> a PFNMAP.
>
>
> But more importantly, we rely on "/proc/iomem" to find a RAM target in
> /dev/mem. That doesn't make any sense with what you are doing here.
>
> If we are not provided /dev/mem, you should probably try mapping offset
> 0 of the file.
>
> --
> Cheers,
>
> David / dhildenb
>