[PATCH v4 1/7] KVM: selftests: Extract guts of THP accessor to standalone sysfs helpers

James Houghton
2025-05-08T18:46:52Z

From: Sean Christopherson <seanjc@google.com>

Extract the guts of thp_configured() and get_trans_hugepagesz() to
standalone helpers so that the core logic can be reused for other sysfs
files, e.g. to query numa_balancing.

Opportunistically assert that the initial fscanf() read at least one byte,
and add a comment explaining the second call to fscanf().

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: James Houghton <jthoughton@google.com>
---
tools/testing/selftests/kvm/lib/test_util.c | 35 ++++++++++++++-------
1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 8ed0b74ae8373..3dc8538f5d696 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -132,37 +132,50 @@ void print_skip(const char *fmt, ...)
puts(", skipping test");
}

-bool thp_configured(void)
+static bool test_sysfs_path(const char *path)
{
- int ret;
struct stat statbuf;
+ int ret;

- ret = stat("/sys/kernel/mm/transparent_hugepage", &statbuf);
+ ret = stat(path, &statbuf);
TEST_ASSERT(ret == 0 || (ret == -1 && errno == ENOENT),
- "Error in stating /sys/kernel/mm/transparent_hugepage");
+ "Error in stat()ing '%s'", path);

return ret == 0;
}

-size_t get_trans_hugepagesz(void)
+bool thp_configured(void)
+{
+ return test_sysfs_path("/sys/kernel/mm/transparent_hugepage");
+}
+
+static size_t get_sysfs_val(const char *path)
{
size_t size;
FILE *f;
int ret;

- TEST_ASSERT(thp_configured(), "THP is not configured in host kernel");
-
- f = fopen("/sys/kernel/mm/transparent_hugepage/hpage_pmd_size", "r");
- TEST_ASSERT(f != NULL, "Error in opening transparent_hugepage/hpage_pmd_size");
+ f = fopen(path, "r");
+ TEST_ASSERT(f, "Error opening '%s'", path);

ret = fscanf(f, "%ld", &size);
+ TEST_ASSERT(ret > 0, "Error reading '%s'", path);
+
+ /* Re-scan the input stream to verify the entire file was read. */
ret = fscanf(f, "%ld", &size);
- TEST_ASSERT(ret < 1, "Error reading transparent_hugepage/hpage_pmd_size");
- fclose(f);
+ TEST_ASSERT(ret < 1, "Error reading '%s'", path);

+ fclose(f);
return size;
}

+size_t get_trans_hugepagesz(void)
+{
+ TEST_ASSERT(thp_configured(), "THP is not configured in host kernel");
+
+ return get_sysfs_val("/sys/kernel/mm/transparent_hugepage/hpage_pmd_size");
+}
+
size_t get_def_hugetlb_pagesz(void)
{
char buf[64];
--
2.49.0.1015.ga840276032-goog