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Sender: Guenter Roeck <groeck7@gmail.com>
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Date: Mon, 5 Feb 2024 08:06:03 -0800
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Subject: Re: Kunit test failures with cpumask tests on parisc
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To: Helge Deller <deller@gmx.de>, Yury Norov <yury.norov@gmail.com>
Cc: James.Bottomley@hansenpartnership.com, linux-parisc@vger.kernel.org,
 Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
 Rasmus Villemoes <linux@rasmusvillemoes.dk>, linux-kernel@vger.kernel.org
References: <e6f0ab85-5bbe-41c1-8976-5ba00044998c@roeck-us.net>
 <929506cf-a1a7-436e-938d-4e5eff0181e4@gmx.de>
From: Guenter Roeck <linux@roeck-us.net>
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On 2/5/24 01:28, Helge Deller wrote:
> On 2/5/24 07:53, Guenter Roeck wrote:
>> when running cpumask Kunit tests on parisc/parisc64 in qemu,
>> I get the following errors.
>>
>>        KTAP version 1
>>        # Subtest: cpumask
>>        # module: cpumask_kunit
>>        1..6
>>        # test_cpumask_weight: EXPECTATION FAILED at lib/cpumask_kunit.c:68
>>        Expected nr_cpu_ids == cpumask_weight(((const struct cpumask *)&__cpu_possible_mask)), but
>>            nr_cpu_ids == 16 (0x10)
>>            cpumask_weight(((const struct cpumask *)&__cpu_possible_mask)) == 1 (0x1)
>>    cpu_possible_mask contains CPUs 0
>>        not ok 1 test_cpumask_weight
>>        # test_cpumask_first: EXPECTATION FAILED at lib/cpumask_kunit.c:79
>>        Expected nr_cpu_ids <= cpumask_first_zero(((const struct cpumask *)&__cpu_possible_mask)), but
>>            nr_cpu_ids == 16 (0x10)
>>            cpumask_first_zero(((const struct cpumask *)&__cpu_possible_mask)) == 1 (0x1)
>>    cpu_possible_mask contains CPUs 0
>>        not ok 2 test_cpumask_first
>>        # test_cpumask_last: EXPECTATION FAILED at lib/cpumask_kunit.c:87
>>        Expected nr_cpu_ids - 1 == cpumask_last(((const struct cpumask *)&__cpu_possible_mask)), but
>>            nr_cpu_ids - 1 == 15 (0xf)
>>            cpumask_last(((const struct cpumask *)&__cpu_possible_mask)) == 0 (0x0)
>>    cpu_possible_mask contains CPUs 0
>>        not ok 3 test_cpumask_last
>>        # test_cpumask_next: EXPECTATION FAILED at lib/cpumask_kunit.c:94
>>        Expected nr_cpu_ids <= cpumask_next_zero(-1, ((const struct cpumask *)&__cpu_possible_mask)), but
>>            nr_cpu_ids == 16 (0x10)
>>            cpumask_next_zero(-1, ((const struct cpumask *)&__cpu_possible_mask)) == 1 (0x1)
>>    cpu_possible_mask contains CPUs 0
>>        not ok 4 test_cpumask_next
>>        ok 5 test_cpumask_iterators
>>        ok 6 test_cpumask_iterators_builtin
>>    # cpumask: pass:2 fail:4 skip:0 total:6
>>    # Totals: pass:2 fail:4 skip:0 total:6
>>    not ok 5 cpumask
>>
>> It appears that parisc sets __cpu_possible_mask to the number of online CPUs,
>> which is limited in qemu and doesn't match CONFIG_NR_CPUS. Is this a problem
>> with the unit test or with the parisc architecture, or does the unit test
>> simply not apply for parisc ?
> 
> Thank you for finding and reporting this!
> It's a bug (or a misunderstanding) in the parisc kernel.
> Reverting commit 0921244f6f4f ("parisc: Only list existing CPUs in cpu_possible_mask")
> fixes the KUnit test.
> 
> Furthermore the revert fixes the issue that CPU hot-unplugging doesn't
> work and which I just was starting to debug:
> https://lore.kernel.org/lkml/Zb0mbHlIud_bqftx@slm.duckdns.org/t/
> 

Glad to help, and thanks for the update.

Guenter