From: Kunwu Chan <kunwu.chan@hotmail.com>
To: Sean Christopherson <seanjc@google.com>,
Andrew Jones <ajones@ventanamicro.com>,
chentao@kylinos.cn
Cc: Markus Elfring <Markus.Elfring@web.de>,
linux-kselftest@vger.kernel.org, kvm@vger.kernel.org,
kernel-janitors@vger.kernel.org,
Muhammad Usama Anjum <usama.anjum@collabora.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Shuah Khan <shuah@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Kunwu Chan <kunwu.chan@hotmail.com>,
Anup Patel <anup@brainfault.org>, Thomas Huth <thuth@redhat.com>,
Oliver Upton <oliver.upton@linux.dev>
Subject: Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state
Date: Wed, 24 Apr 2024 10:59:31 +0800 [thread overview]
Message-ID: <DS7PR11MB7784C50A318F0FA92CC334EF97102@DS7PR11MB7784.namprd11.prod.outlook.com> (raw)
In-Reply-To: <ZigI48_cI7Twb9gD@google.com>
Thanks all for the reply.
On 2024/4/24 03:15, Sean Christopherson wrote:
> On Tue, Apr 23, 2024, Andrew Jones wrote:
>> On Tue, Apr 23, 2024 at 07:56:01AM -0700, Sean Christopherson wrote:
>>> +others
>>>
>>> On Tue, Apr 23, 2024, Markus Elfring wrote:
>>>> …
>>>>> This patch will add the malloc failure checking
>>>> …
>>>>
>>>> * Please use a corresponding imperative wording for the change description.
>>>>
>>>> * Would you like to add the tag “Fixes” accordingly?
>>> Nah, don't bother with Fixes. OOM will cause the test to fail regardless, the
>>> fact that it gets an assert instead a NULL pointer deref is nice to have, but by
>>> no means does it fix a bug.
>>>
>>>>> +++ b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
>>>>> @@ -91,6 +91,7 @@ void test_vmx_nested_state(struct kvm_vcpu *vcpu)
>>>>> const int state_sz = sizeof(struct kvm_nested_state) + getpagesize();
>>>>> struct kvm_nested_state *state =
>>>>> (struct kvm_nested_state *)malloc(state_sz);
>>>>> + TEST_ASSERT(state, "-ENOMEM when allocating kvm state");
>>>> …
>>>>
>>>> Can “errno” be relevant for the error message construction?
>>> Probably not, but there's also no reason to assume ENOMEM. TEST_ASSERT() spits
>>> out the actual errno, and we can just say something like "malloc() failed for
>>> blah blah blah".
>>>
>>> But rather than keeping playing whack-a-mole, what if we add macros to perform
>>> allocations and assert on the result? I have zero interest in chasing down all
>>> of the "unsafe" allocations, and odds are very good that we'll collectively fail
>>> to enforce checking on new code.
>>>
>>> E.g. something like (obviously won't compile, just for demonstration purposes)
>>>
>>> #define kvm_malloc(x)
>>> ({
>>> void *__ret;
>>>
>>> __ret = malloc(x);
>>> TEST_ASSERT(__ret, "Failed malloc(" #x ")\n");
>>> __ret;
>>> })
>>>
>>> #define kvm_calloc(x, y)
>>> ({
>>> void *__ret;
>>>
>>> __ret = calloc(x, y);
>>> TEST_ASSERT(__ret, "Failed calloc(" #x ", " #y ")\n");
>>> __ret;
>>> })
>> Sounds good to me, but I'd call them test_malloc, test_calloc, etc. and
>> put them in include/test_util.h
> Possibly terrible idea: what if we used kmalloc() and kcalloc()? K is for KVM :-)
I'am agree with that we should keep opening state for other memory
allocate calls as well.
> I like test_* more than kvm_*, but I'm mildly concerned that readers will be
> confused by "test", e.g. initially thinking the "test" means it's just "testing"
> if allocation is possible.
>
> The obvious counter-argument is that people might also get tripped by kmalloc(),
> e.g. thinking that selftests is somehow doing a kernel allocation.
>
> I almost wonder if we should just pick a prefix that's less obviously connected
> to KVM and/or selftests, but unique and short.
It's a good idea. The marco should be more versatile, cause we had many
different way in selftests to check the null pointer or fail state, such
as '
ksft_exit_fail_*' 'ASSERT_*' 'CHECK*' or just use if statement.
Different part different developer has different usage habits.
We should think these status quo before doing sth.
>
> Hmm, tmalloc(), i.e t[est]malloc()? tcalloc() gets a bit close to Google's
> TCMalloc[*], but I suspect that any confusion would be entirely limited to
> Googlers, and I'll volunteer us to suck it up and deal with it :-)
>
> [*] https://github.com/google/tcmalloc
And another question is if we add a new macro, whether these old usage
should be changed as well.
Thanks for your reply.
Looking forward to your reply.
next prev parent reply other threads:[~2024-04-24 2:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-23 7:39 [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state Kunwu Chan
2024-04-23 8:49 ` Muhammad Usama Anjum
2024-04-23 10:45 ` Markus Elfring
2024-04-23 14:56 ` Sean Christopherson
2024-04-23 15:14 ` Andrew Jones
2024-04-23 19:15 ` Sean Christopherson
2024-04-24 2:59 ` Kunwu Chan [this message]
2024-04-24 5:41 ` Dan Carpenter
2024-04-24 14:47 ` Sean Christopherson
2024-04-24 7:50 ` Andrew Jones
2024-04-24 14:51 ` Sean Christopherson
2024-04-24 17:18 ` Oliver Upton
2024-04-25 16:25 ` Sean Christopherson
2024-05-10 8:40 ` Kunwu Chan
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