linux-kernel - [RFC PATCH v4 6/9] KVM: selftests: Add a helper to get system default hugetlb page size

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Message-ID: <20210302125751.19080-7-wangyanan55@huawei.com>
Date:   Tue, 2 Mar 2021 20:57:48 +0800
From:   Yanan Wang <wangyanan55@...wei.com>
To:     <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Ben Gardon <bgardon@...gle.com>,
        "Sean Christopherson" <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        Peter Xu <peterx@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        <wanghaibin.wang@...wei.com>, <yezengruan@...wei.com>,
        <yuzenghui@...wei.com>, Yanan Wang <wangyanan55@...wei.com>
Subject: [RFC PATCH v4 6/9] KVM: selftests: Add a helper to get system default hugetlb page size

If HUGETLB is configured in the host kernel, then we can know the system
default hugetlb page size through *cat /proc/meminfo*. Otherwise, we will
not see the information of hugetlb pages in file /proc/meminfo if it's not
configured. So add a helper to determine whether HUGETLB is configured and
then get the default page size by reading /proc/meminfo.

This helper can be useful when a program wants to use the default hugetlb
pages of the system and doesn't know the default page size.

Signed-off-by: Yanan Wang <wangyanan55@...wei.com>
---
 .../testing/selftests/kvm/include/test_util.h |  1 +
 tools/testing/selftests/kvm/lib/test_util.c   | 27 +++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index ef24c76ba89a..e087174eefe5 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -80,6 +80,7 @@ struct vm_mem_backing_src_alias {
 
 bool thp_configured(void);
 size_t get_trans_hugepagesz(void);
+size_t get_def_hugetlb_pagesz(void);
 void backing_src_help(void);
 enum vm_mem_backing_src_type parse_backing_src_type(const char *type_name);
 
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index f2d133f76c67..80d68dbd72d2 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -153,6 +153,33 @@ size_t get_trans_hugepagesz(void)
 	return size;
 }
 
+size_t get_def_hugetlb_pagesz(void)
+{
+	char buf[64];
+	const char *tag = "Hugepagesize:";
+	FILE *f;
+
+	f = fopen("/proc/meminfo", "r");
+	TEST_ASSERT(f != NULL, "Error in opening /proc/meminfo: %d", errno);
+
+	while (fgets(buf, sizeof(buf), f) != NULL) {
+		if (strstr(buf, tag) == buf) {
+			fclose(f);
+			return strtoull(buf + strlen(tag), NULL, 10) << 10;
+		}
+	}
+
+	if (feof(f)) {
+		fclose(f);
+		TEST_FAIL("HUGETLB is not configured in host kernel");
+	} else {
+		fclose(f);
+		TEST_FAIL("Error in reading /proc/meminfo: %d", errno);
+	}
+
+	return 0;
+}
+
 void backing_src_help(void)
 {
 	int i;
-- 
2.23.0