linux-kernel - Re: [PATCH v1 01/24] LoongArch: KVM: Implement kvm module related interface

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Date:   Tue, 14 Feb 2023 21:05:40 +0800
From:   maobibo <maobibo@...ngson.cn>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tianrui Zhao <zhaotianrui@...ngson.cn>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>, Mark Brown <broonie@...nel.org>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH v1 01/24] LoongArch: KVM: Implement kvm module related
 interface



在 2023/2/14 17:58, Greg Kroah-Hartman 写道:
> On Tue, Feb 14, 2023 at 05:00:56PM +0800, Tianrui Zhao wrote:
>>>> +#define KVM_GET_CSRS		_IOWR(KVMIO, 0xc5, struct kvm_csrs)
>>>> +#define KVM_SET_CSRS		_IOW(KVMIO,  0xc6, struct kvm_csrs)
>>> Why does this arch need new ioctls?
>> We want to use this ioctl to access multiple csrs at one time. If without
>> this, we only access one csr.
> 
> What is wrong with accessing only one csr at a time?  Isn't this what
> other architectures do?
It is ok to access CSR register once at a time, the other platforms do this
except x86 platform. Only that I think that batch method is better such as
KVM_GET/SET_MSRS ioctl cmds in x86. 

Regards
Bibo, Mao
> 
>> There is another function, can we use the KVM_GET/SET_MSRS to access our
>> csrs?
> 
> I do not know, that's up to the KVM developers to answer.
> 
> thanks,
> 
> greg k-h