Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Reply-To: Gavin Shan <gshan@redhat.com>
Subject: Re: [PATCH 2/2] KVM: selftests: Use getcpu() instead of
 sched_getcpu() in rseq_test
To:     Florian Weimer <fweimer@redhat.com>
Cc:     kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
        pbonzini@redhat.com, maz@kernel.org, oliver.upton@linux.dev,
        andrew.jones@linux.dev, seanjc@google.com,
        mathieu.desnoyers@efficios.com, yihyu@redhat.com,
        shan.gavin@gmail.com
References: <20220809060627.115847-1-gshan@redhat.com>
 <20220809060627.115847-3-gshan@redhat.com>
 <87y1vxncv1.fsf@oldenburg.str.redhat.com>
 <87mtcdnaxe.fsf@oldenburg.str.redhat.com>
From:   Gavin Shan <gshan@redhat.com>
Message-ID: <ea2ef1a2-0fd8-448b-d7ca-254603518823@redhat.com>
Date:   Tue, 9 Aug 2022 18:46:39 +1000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.2.0
MIME-Version: 1.0
In-Reply-To: <87mtcdnaxe.fsf@oldenburg.str.redhat.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 8/9/22 5:17 PM, Florian Weimer wrote:
> * Florian Weimer:
> 
>> * Gavin Shan:
>>
>>> sched_getcpu() is glibc dependent and it can simply return the CPU
>>> ID from the registered rseq information, as Florian Weimer pointed.
>>> In this case, it's pointless to compare the return value from
>>> sched_getcpu() and that fetched from the registered rseq information.
>>>
>>> Fix the issue by replacing sched_getcpu() with getcpu(), as Florian
>>> suggested. The comments are modified accordingly.
>>
>> Note that getcpu was added in glibc 2.29, so perhaps you need to perform
>> a direct system call?
> 
> One more thing: syscall(__NR_getcpu) also has the advantage that it
> wouldn't have to be changed again if node IDs become available via rseq
> and getcpu is implemented using that.
> 
> Thanks,
> Florian
> 

Thanks, Florian. It makes sense to me to use syscall(__NR_getcpu) in
next revision. Thanks for your quick review :)

I would hold for one or two days to post v2, to see if others have
more comments.

Thanks,
Gavin