Message-ID: <d6e794c7-4741-a656-07ae-1cad4c26d93e@redhat.com>
Date:   Tue, 21 Feb 2023 07:49:49 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
Subject: Re: [PATCH v2 01/29] LoongArch: KVM: Add kvm related header files
Content-Language: en-US
To:     Tianrui Zhao <zhaotianrui@loongson.cn>
Cc:     Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        loongarch@lists.linux.dev, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        Mark Brown <broonie@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Oliver Upton <oliver.upton@linux.dev>, maobibo@loongson.cn
References: <20230220065735.1282809-1-zhaotianrui@loongson.cn>
 <20230220065735.1282809-2-zhaotianrui@loongson.cn>
 <2b047b75-7397-0cce-e7af-ebba67ae2561@redhat.com>
 <c9dada46-829c-d3cd-c3b6-68a570552e84@loongson.cn>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <c9dada46-829c-d3cd-c3b6-68a570552e84@loongson.cn>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 2/21/23 03:56, Tianrui Zhao wrote:
>>
>> In _kvm_check_vmid(), you already have
>>
>> +    if (migrated || (ver != old)) {
>> +        _kvm_update_vpid(vcpu, cpu);
>> +        trace_kvm_vpid_change(vcpu, vcpu->arch.vpid[cpu]);
>> +    }
>>
>> so a vpid will never be recycled if a vCPU migrates from physical CPU 
>> A to B and back to A.
>>
>> So please keep the current VPID in the per-cpu struct vmcs, and you 
>> can just copy it from there in _kvm_check_vmid().
> 
> Thanks,  that is to say we should remove the vpid[NR_CPUS] array and it 
> is enough to use only one vpid variable?

Yes, you need a vpid variable here and one in struct kvm_context.

Paolo