linux-kernel - Re: [PATCH v2 3/3] LoongArch: Add paravirt preempt print prompt

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Message-ID: <fa25523c-4913-186b-caea-d7a46d52a71e@loongson.cn>
Date: Mon, 24 Nov 2025 15:10:10 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Juergen Gross <jgross@...e.com>,
 Ajay Kaher <ajay.kaher@...adcom.com>,
 Alexey Makhalov <alexey.makhalov@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, WANG Xuerui <kernel@...0n.name>,
 kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev, x86@...nel.org
Subject: Re: [PATCH v2 3/3] LoongArch: Add paravirt preempt print prompt



On 2025/11/24 下午2:33, Huacai Chen wrote:
> Hi, Bibo,
> 
> On Mon, Nov 24, 2025 at 11:54 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> Add paravirt preempt print prompt together with steal timer information,
>> so that it is easy to check whether paravirt preempt feature is enabled
>> or not.
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>>   arch/loongarch/kernel/paravirt.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
>> index d4163679adc4..ffe1cf284c41 100644
>> --- a/arch/loongarch/kernel/paravirt.c
>> +++ b/arch/loongarch/kernel/paravirt.c
>> @@ -300,6 +300,7 @@ static struct notifier_block pv_reboot_nb = {
>>   int __init pv_time_init(void)
>>   {
>>          int r;
>> +       bool pv_preempted = false;
>>
>>          if (!kvm_para_has_feature(KVM_FEATURE_STEAL_TIME))
>>                  return 0;
>> @@ -322,8 +323,10 @@ int __init pv_time_init(void)
>>                  return r;
>>          }
>>
>> -       if (kvm_para_has_feature(KVM_FEATURE_PREEMPT))
>> +       if (kvm_para_has_feature(KVM_FEATURE_PREEMPT)) {
>>                  static_branch_enable(&virt_preempt_key);
>> +               pv_preempted = true;
>> +       }
>>   #endif
>>
>>          static_call_update(pv_steal_clock, paravt_steal_clock);
>> @@ -334,7 +337,10 @@ int __init pv_time_init(void)
>>                  static_key_slow_inc(&paravirt_steal_rq_enabled);
>>   #endif
>>
>> -       pr_info("Using paravirt steal-time\n");
>> +       if (pv_preempted)
> No pv_preempted needed, you can just use
> static_key_enabled(&virt_preempt_key) and merge this patch to Patch-2.
yes, good idea.
Will do in next version with these two points.

Regards
Bibo Mao
> 
> 
> Huacai
> 
>> +               pr_info("Using paravirt steal-time with preempt hint enabled\n");
>> +       else
>> +               pr_info("Using paravirt steal-time with preempt hint disabled\n");
>>
>>          return 0;
>>   }
>> --
>> 2.39.3
>>