linux-kernel - Re: [PATCH v2 2/3] LoongArch: Add paravirt support with vcpu_is

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Message-ID: <47fed3cd-58fd-4670-a939-7b2e7ca1b673@suse.com>
Date: Mon, 24 Nov 2025 07:55:46 +0100
From: Jürgen Groß <jgross@...e.com>
To: Huacai Chen <chenhuacai@...nel.org>, Bibo Mao <maobibo@...ngson.cn>
Cc: Paolo Bonzini <pbonzini@...hat.com>, WANG Xuerui <kernel@...0n.name>,
 Ajay Kaher <ajay.kaher@...adcom.com>,
 Alexey Makhalov <alexey.makhalov@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, kvm@...r.kernel.org,
 loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
 virtualization@...ts.linux.dev, x86@...nel.org
Subject: Re: [PATCH v2 2/3] LoongArch: Add paravirt support with
 vcpu_is_preempted() in guest side

On 24.11.25 07:33, Huacai Chen wrote:
> Hi, Bibo,
> 
> On Mon, Nov 24, 2025 at 11:54 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> Function vcpu_is_preempted() is used to check whether vCPU is preempted
>> or not. Here add implementation with vcpu_is_preempted() when option
>> CONFIG_PARAVIRT is enabled.
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>>   arch/loongarch/include/asm/qspinlock.h |  5 +++++
>>   arch/loongarch/kernel/paravirt.c       | 16 ++++++++++++++++
>>   2 files changed, 21 insertions(+)
>>
>> diff --git a/arch/loongarch/include/asm/qspinlock.h b/arch/loongarch/include/asm/qspinlock.h
>> index e76d3aa1e1eb..9a5b7ba1f4cb 100644
>> --- a/arch/loongarch/include/asm/qspinlock.h
>> +++ b/arch/loongarch/include/asm/qspinlock.h
>> @@ -34,6 +34,11 @@ static inline bool virt_spin_lock(struct qspinlock *lock)
>>          return true;
>>   }
>>
>> +#ifdef CONFIG_SMP
>> +#define vcpu_is_preempted      vcpu_is_preempted
>> +bool vcpu_is_preempted(int cpu);
> In V1 there is a build error because you reference mp_ops, so in V2
> you needn't put it in CONFIG_SMP.
> On the other hand, even if you really build a UP guest kernel, when
> multiple guests run together, you probably need vcpu_is_preemtped.

I don't think so. When the UP guest's vcpu is preempted, who will use this
function?


Juergen

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