linux-kernel - [PATCH V2] SelfTest: KVM: Drop Asserts for madvise MADV

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Date:   Fri, 16 Nov 2018 13:50:55 +0200
From:   Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>
To:     Shuah Khan <shuah@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Colin Ian King <colin.king@...onical.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hossam Hassan <7ossam9063@...il.com>,
        Ahmed Lotfy <A7med.lotfey@...il.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Anders Roxell <anders.roxell@...aro.org>
Cc:     Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>
Subject: [PATCH V2] SelfTest: KVM: Drop Asserts for madvise MADV_NOHUGEPAGE failure

From: Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>

madvise() returns -1 without CONFIG_TRANSPARENT_HUGEPAGE=y. That would
trigger asserts when checking for return value of madvice. Following
similar decision to [1]. I thought it is ok to assume that madvise()
MADV_NOHUGEPAGE failures implies that THP is not supported by host kernel.

Other options was to check for Transparent Huge Page support in
/sys/kernel/mm/transparent_hugepage/enabled.

-- links --
[1] https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg04514.html

Signed-off-by: Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 1b41e71283d5..437c5bb48061 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -586,14 +586,23 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 				 src_type == VM_MEM_SRC_ANONYMOUS_THP ?  huge_page_size : 1);
 
 	/* As needed perform madvise */
-	if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
+	if (src_type == VM_MEM_SRC_ANONYMOUS) {
+		/*
+		 * Neglect madvise error because it is ok to not have THP
+		 * support in this case.
+		 */
+		madvise(region->host_mem, npages * vm->page_size,
+			MADV_NOHUGEPAGE);
+	} else if (src_type == VM_MEM_SRC_ANONYMOUS_THP) {
 		ret = madvise(region->host_mem, npages * vm->page_size,
-			     src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
+			MADV_HUGEPAGE);
 		TEST_ASSERT(ret == 0, "madvise failed,\n"
-			    "  addr: %p\n"
-			    "  length: 0x%lx\n"
-			    "  src_type: %x",
-			    region->host_mem, npages * vm->page_size, src_type);
+			"Does the kernel have CONFIG_TRANSPARENT_HUGEPAGE=y\n"
+			"  addr: %p\n"
+			"  length: 0x%lx\n"
+			"  src_type: %x\n",
+			region->host_mem, npages * vm->page_size,
+			src_type);
 	}
 
 	region->unused_phy_pages = sparsebit_alloc();
-- 
2.18.1