Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Markus Elfring]

…
> 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?


…
> +++ 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?

Regards,
Markus

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Sean Christopherson]

+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;
})

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Andrew Jones]

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

Thanks,
drew

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Sean Christopherson]

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 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.

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

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Kunwu Chan]

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.

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Dan Carpenter]

On Tue, Apr 23, 2024 at 12:15:47PM -0700, 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 :-)

That's a legit terrible idea...  It probably would trigger more static
checker warnings because the general policy is kmalloc() is kernel code
and we *have* to test for errors.

To be honest, I would have just rejected the first patch.  You
obviously know this and have said this earlier in the thread but just
for the other people, this is a userspace test that runs for a short
time and then exits.  If it gets killed because we don't have enough
memory that's fine.  It would be better to just fix the static checker
to not print pointless warnings or educate people to ignore warnings
like this.

Creating the test_malloc() to silence the warning also seems like an
okay idea as well.

regards,
dan carpenter

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Andrew Jones]

On Tue, Apr 23, 2024 at 12:15:47PM -0700, Sean Christopherson wrote:
...
> I almost wonder if we should just pick a prefix that's less obviously connected
> to KVM and/or selftests, but unique and short.
>

How about kvmsft_ ? It's based on the ksft_ prefix of kselftest.h. Maybe
it's too close to ksft though and would be confusing when using both in
the same test? I'm not a huge fan of capital letters, but we could also
do something like MALLOC()/CALLOC(). Eh, I don't know. Naming is hard.

Thanks,
drew

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Sean Christopherson]

On Wed, Apr 24, 2024, Dan Carpenter wrote:
> On Tue, Apr 23, 2024 at 12:15:47PM -0700, 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 :-)
> 
> That's a legit terrible idea...  It probably would trigger more static
> checker warnings because the general policy is kmalloc() is kernel code
> and we *have* to test for errors.

Roger that.

> To be honest, I would have just rejected the first patch.  You
> obviously know this and have said this earlier in the thread but just
> for the other people, this is a userspace test that runs for a short
> time and then exits.  If it gets killed because we don't have enough
> memory that's fine.  It would be better to just fix the static checker
> to not print pointless warnings or educate people to ignore warnings
> like this.

This particular patch may have been motiviated by a static checker, but I doubt
static checkers are responsible for all of the many sanity checks on malloc() in
KVM selftests.  And while I agree that the sanity checks don't and much value,
deleting the existing checks and preventing checks from being reintroduced would
be a never ending battle.

> Creating the test_malloc() to silence the warning also seems like an
> okay idea as well.

Yeah, it's not exactly my first choice, but the reality is that people write KVM
elftests by copying an existing test (often literally), and so the best way to
educate developers on the preferred approach/style is to have all existing code
adhere to a single approach/style.

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Sean Christopherson]

On Wed, Apr 24, 2024, Andrew Jones wrote:
> On Tue, Apr 23, 2024 at 12:15:47PM -0700, Sean Christopherson wrote:
> ...
> > I almost wonder if we should just pick a prefix that's less obviously connected
> > to KVM and/or selftests, but unique and short.
> >
> 
> How about kvmsft_ ? It's based on the ksft_ prefix of kselftest.h. Maybe
> it's too close to ksft though and would be confusing when using both in
> the same test?

I would prefer something short, and for whatever reason I have a mental block
with ksft.  I always read it as "k soft", which is completely nonsensical :-)

> I'm not a huge fan of capital letters, but we could also do something like
> MALLOC()/CALLOC().

Hmm, I'm not usually a fan either, but that could actually work quite well in this
case.  It would be quite intuitive, easy to visually parse whereas tmalloc() vs
malloc() kinda looks like a typo, and would more clearly communicate that they're
macros.

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Oliver Upton]

Hey,

On Wed, Apr 24, 2024 at 07:51:44AM -0700, Sean Christopherson wrote:
> On Wed, Apr 24, 2024, Andrew Jones wrote:
> > On Tue, Apr 23, 2024 at 12:15:47PM -0700, Sean Christopherson wrote:
> > ...
> > > I almost wonder if we should just pick a prefix that's less obviously connected
> > > to KVM and/or selftests, but unique and short.
> > >
> > 
> > How about kvmsft_ ? It's based on the ksft_ prefix of kselftest.h. Maybe
> > it's too close to ksft though and would be confusing when using both in
> > the same test?
> 
> I would prefer something short, and for whatever reason I have a mental block
> with ksft.  I always read it as "k soft", which is completely nonsensical :-)

I despise brevity in tests, so my strong preference is to use some form
of 'namespaced' helper. Perhaps others have better memory than
I do, but I'm quick to forget the selftests library and find the more
verbose / obvious function names helpful for jogging my memory.

> > I'm not a huge fan of capital letters, but we could also do something like
> > MALLOC()/CALLOC().
> 
> Hmm, I'm not usually a fan either, but that could actually work quite well in this
> case.  It would be quite intuitive, easy to visually parse whereas tmalloc() vs
> malloc() kinda looks like a typo, and would more clearly communicate that they're
> macros.

Ooo, don't leave me out on the bikeshedding! How about TEST_MALLOC() /
TEST_CALLOC(). It is vaguely similar to TEST_ASSERT(), which I'd hope
would give the impression that an assertion is lurking below.

-- 
Thanks,
Oliver

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Sean Christopherson]

On Wed, Apr 24, 2024, Oliver Upton wrote:
> Hey,
> 
> On Wed, Apr 24, 2024 at 07:51:44AM -0700, Sean Christopherson wrote:
> > On Wed, Apr 24, 2024, Andrew Jones wrote:
> > > On Tue, Apr 23, 2024 at 12:15:47PM -0700, Sean Christopherson wrote:
> > > ...
> > > > I almost wonder if we should just pick a prefix that's less obviously connected
> > > > to KVM and/or selftests, but unique and short.
> > > >
> > > 
> > > How about kvmsft_ ? It's based on the ksft_ prefix of kselftest.h. Maybe
> > > it's too close to ksft though and would be confusing when using both in
> > > the same test?
> > 
> > I would prefer something short, and for whatever reason I have a mental block
> > with ksft.  I always read it as "k soft", which is completely nonsensical :-)
> 
> I despise brevity in tests, so my strong preference is to use some form
> of 'namespaced' helper. Perhaps others have better memory than
> I do, but I'm quick to forget the selftests library and find the more
> verbose / obvious function names helpful for jogging my memory.

Hmm, I generally agree, but in this case I think there's value in having the
names *not* stand out, because they really are uninteresting and would ideally
blend in.  I can't envision a scenario where we don't want to assert on an OOM,
i.e. there should never be a need to use a raw malloc(), and so I don't see much
value in making it obvious that the call sites are doing something special.

> > > I'm not a huge fan of capital letters, but we could also do something like
> > > MALLOC()/CALLOC().
> > 
> > Hmm, I'm not usually a fan either, but that could actually work quite well in this
> > case.  It would be quite intuitive, easy to visually parse whereas tmalloc() vs
> > malloc() kinda looks like a typo, and would more clearly communicate that they're
> > macros.
> 
> Ooo, don't leave me out on the bikeshedding! How about TEST_MALLOC() /
> TEST_CALLOC(). It is vaguely similar to TEST_ASSERT(), which I'd hope
> would give the impression that an assertion is lurking below.

Yeah, but it could also give the false impression that the macro does something
fancier, e.g. this makes me want to peek at TEST_MALLOC() to see what it's doing

	cpuid = TEST_MALLOC(kvm_cpuid2_size(nr_entries));

whereas this isn't quite enough to pique my curiosity.

	cpuid = MALLOC(kvm_cpuid2_size(nr_entries));

So I have a slight preference for just MALLOC()/CALLOC(), but I'm also ok with a
TEST_ prefix, my brain can adapt.  One of those two flavors has my vote.

Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

[Kunwu Chan]

Thanks for reply.

On 2024/4/26 00:25, Sean Christopherson wrote:
> On Wed, Apr 24, 2024, Oliver Upton wrote:
>> Hey,
>>
>> On Wed, Apr 24, 2024 at 07:51:44AM -0700, Sean Christopherson wrote:
>>> On Wed, Apr 24, 2024, Andrew Jones wrote:
>>>> On Tue, Apr 23, 2024 at 12:15:47PM -0700, Sean Christopherson wrote:
>>>> ...
>>>>> I almost wonder if we should just pick a prefix that's less obviously connected
>>>>> to KVM and/or selftests, but unique and short.
>>>>>
>>>> How about kvmsft_ ? It's based on the ksft_ prefix of kselftest.h. Maybe
>>>> it's too close to ksft though and would be confusing when using both in
>>>> the same test?
>>> I would prefer something short, and for whatever reason I have a mental block
>>> with ksft.  I always read it as "k soft", which is completely nonsensical :-)
>> I despise brevity in tests, so my strong preference is to use some form
>> of 'namespaced' helper. Perhaps others have better memory than
>> I do, but I'm quick to forget the selftests library and find the more
>> verbose / obvious function names helpful for jogging my memory.
> Hmm, I generally agree, but in this case I think there's value in having the
> names *not* stand out, because they really are uninteresting and would ideally
> blend in.  I can't envision a scenario where we don't want to assert on an OOM,
> i.e. there should never be a need to use a raw malloc(), and so I don't see much
> value in making it obvious that the call sites are doing something special.
>
>>>> I'm not a huge fan of capital letters, but we could also do something like
>>>> MALLOC()/CALLOC().
>>> Hmm, I'm not usually a fan either, but that could actually work quite well in this
>>> case.  It would be quite intuitive, easy to visually parse whereas tmalloc() vs
>>> malloc() kinda looks like a typo, and would more clearly communicate that they're
>>> macros.
>> Ooo, don't leave me out on the bikeshedding! How about TEST_MALLOC() /
>> TEST_CALLOC(). It is vaguely similar to TEST_ASSERT(), which I'd hope
>> would give the impression that an assertion is lurking below.
> Yeah, but it could also give the false impression that the macro does something
> fancier, e.g. this makes me want to peek at TEST_MALLOC() to see what it's doing
>
> 	cpuid = TEST_MALLOC(kvm_cpuid2_size(nr_entries));
>
> whereas this isn't quite enough to pique my curiosity.
>
> 	cpuid = MALLOC(kvm_cpuid2_size(nr_entries));
>
> So I have a slight preference for just MALLOC()/CALLOC(), but I'm also ok with a
> TEST_ prefix, my brain can adapt.  One of those two flavors has my vote.

According to the previous discussion, so which method do we need to use now?

If you have a consensus, if necessary, I can continue to do this work.

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.

If we add a new macro, whether these old usage should be changed as well.