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Message-ID: <1c5cfc23-3f63-404d-a4bf-030c24412b20@linux.intel.com>
Date: Tue, 27 May 2025 16:53:43 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Ackerley Tng <ackerleytng@...gle.com>, Ira Weiny <ira.weiny@...el.com>
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Subject: Re: [RFC PATCH v2 03/51] KVM: selftests: Update guest_memfd_test for
INIT_PRIVATE flag
On 5/17/2025 1:42 AM, Ackerley Tng wrote:
> Ira Weiny <ira.weiny@...el.com> writes:
>
>> Ackerley Tng wrote:
>>> Test that GUEST_MEMFD_FLAG_INIT_PRIVATE is only valid when
>>> GUEST_MEMFD_FLAG_SUPPORT_SHARED is set.
>>>
>>> Change-Id: I506e236a232047cfaee17bcaed02ee14c8d25bbb
>>> Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
>>> ---
>>> .../testing/selftests/kvm/guest_memfd_test.c | 36 ++++++++++++-------
>>> 1 file changed, 24 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
>>> index 60aaba5808a5..bf2876cbd711 100644
>>> --- a/tools/testing/selftests/kvm/guest_memfd_test.c
>>> +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
>>> @@ -401,13 +401,31 @@ static void test_with_type(unsigned long vm_type, uint64_t guest_memfd_flags,
>>> kvm_vm_release(vm);
>>> }
>>>
>>> +static void test_vm_with_gmem_flag(struct kvm_vm *vm, uint64_t flag,
>>> + bool expect_valid)
>>> +{
>>> + size_t page_size = getpagesize();
>>> + int fd;
>>> +
>>> + fd = __vm_create_guest_memfd(vm, page_size, flag);
>>> +
>>> + if (expect_valid) {
>>> + TEST_ASSERT(fd > 0,
>>> + "guest_memfd() with flag '0x%lx' should be valid",
>>> + flag);
>>> + close(fd);
>>> + } else {
>>> + TEST_ASSERT(fd == -1 && errno == EINVAL,
>>> + "guest_memfd() with flag '0x%lx' should fail with EINVAL",
>>> + flag);
>>> + }
>>> +}
>>> +
>>> static void test_vm_type_gmem_flag_validity(unsigned long vm_type,
>>> uint64_t expected_valid_flags)
>>> {
>>> - size_t page_size = getpagesize();
>>> struct kvm_vm *vm;
>>> uint64_t flag = 0;
>>> - int fd;
>>>
>>> if (!(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(vm_type)))
>>> return;
>>> @@ -415,17 +433,11 @@ static void test_vm_type_gmem_flag_validity(unsigned long vm_type,
>>> vm = vm_create_barebones_type(vm_type);
>>>
>>> for (flag = BIT(0); flag; flag <<= 1) {
>>> - fd = __vm_create_guest_memfd(vm, page_size, flag);
>>> + test_vm_with_gmem_flag(vm, flag, flag & expected_valid_flags);
>>>
>>> - if (flag & expected_valid_flags) {
>>> - TEST_ASSERT(fd > 0,
>>> - "guest_memfd() with flag '0x%lx' should be valid",
>>> - flag);
>>> - close(fd);
>>> - } else {
>>> - TEST_ASSERT(fd == -1 && errno == EINVAL,
>>> - "guest_memfd() with flag '0x%lx' should fail with EINVAL",
>>> - flag);
>>> + if (flag == GUEST_MEMFD_FLAG_SUPPORT_SHARED) {
>>> + test_vm_with_gmem_flag(
>>> + vm, flag | GUEST_MEMFD_FLAG_INIT_PRIVATE, true);
>> I don't understand the point of this check. In 2/51 we set
>> GUEST_MEMFD_FLAG_INIT_PRIVATE when GUEST_MEMFD_FLAG_SUPPORT_SHARED is set.
>>
>> When can this check ever fail?
>>
>> Ira
> In 02/51, GUEST_MEMFD_FLAG_INIT_PRIVATE is not set by default,
> GUEST_MEMFD_FLAG_INIT_PRIVATE is set as one of the valid_flags.
>
> The intention is that GUEST_MEMFD_FLAG_INIT_PRIVATE is only valid if
> GUEST_MEMFD_FLAG_SUPPORT_SHARED is requested by userspace.
>
> In this test, the earlier part before the if block calls
> test_vm_with_gmem_flag() all valid flags, and that already tests
> GUEST_MEMFD_FLAG_SUPPORT_SHARED individually.
>
> Specifically if GUEST_MEMFD_FLAG_SUPPORT_SHARED is set, this if block
> adds a test for when both GUEST_MEMFD_FLAG_SUPPORT_SHARED and
> GUEST_MEMFD_FLAG_INIT_PRIVATE are set, and sets that expect_valid is
> true.
Maybe it's more clear to move this case out of the loop?
>
> This second test doesn't fail, it is meant to check that the kernel
> allows the pair of flags to be set. Hope that makes sense.
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