linux-kernel - [RFC PATCH 34/39] KVM: selftests: Add notes in private_mem_kvm_exits_test for mmap-able guest

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Message-ID: <0ea30ee1128f7e6d033783034b6bc48dfbabb5db.1726009989.git.ackerleytng@google.com>
Date: Tue, 10 Sep 2024 23:44:05 +0000
From: Ackerley Tng <ackerleytng@...gle.com>
To: tabba@...gle.com, quic_eberman@...cinc.com, roypat@...zon.co.uk, 
	jgg@...dia.com, peterx@...hat.com, david@...hat.com, rientjes@...gle.com, 
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Cc: erdemaktas@...gle.com, vannapurve@...gle.com, ackerleytng@...gle.com, 
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	linux-mm@...ck.org, kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-fsdevel@...ck.org
Subject: [RFC PATCH 34/39] KVM: selftests: Add notes in private_mem_kvm_exits_test
 for mmap-able guest_memfd

Note in comments why madvise() is not needed before setting memory to
private.

Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
---
 .../selftests/kvm/x86_64/private_mem_kvm_exits_test.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
index 13e72fcec8dd..f8bcfc897f6a 100644
--- a/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
@@ -62,7 +62,11 @@ static void test_private_access_memslot_deleted(void)
 
 	virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);
 
-	/* Request to access page privately */
+	/*
+	 * Request to access page privately. madvise(MADV_DONTNEED) not required
+	 * since memory was never mmap()-ed from guest_memfd. Anonymous memory
+	 * was used instead for this memslot's userspace_addr.
+	 */
 	vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);
 
 	pthread_create(&vm_thread, NULL,
@@ -98,7 +102,10 @@ static void test_private_access_memslot_not_private(void)
 
 	virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);
 
-	/* Request to access page privately */
+	/*
+	 * Request to access page privately. madvise(MADV_DONTNEED) not required
+	 * since the affected memslot doesn't use guest_memfd.
+	 */
 	vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);
 
 	exit_reason = run_vcpu_get_exit_reason(vcpu);
-- 
2.46.0.598.g6f2099f65c-goog