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Message-ID: <diqzwm9x6f9x.fsf@ackerleytng-ctop.c.googlers.com>
Date: Fri, 30 May 2025 12:59:38 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: Binbin Wu <binbin.wu@...ux.intel.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
Binbin Wu <binbin.wu@...ux.intel.com> writes:
> 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?
>
Will try that in the next revision. Thanks!
>>
>> 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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