linux-kernel - Re: [PATCH v2 06/29] LoongArch: KVM: Implement vcpu create and destroy interface

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Date:   Thu, 23 Feb 2023 09:23:14 +0800
From:   Tianrui Zhao <zhaotianrui@...ngson.cn>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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>,
        Oliver Upton <oliver.upton@...ux.dev>, maobibo@...ngson.cn
Subject: Re: [PATCH v2 06/29] LoongArch: KVM: Implement vcpu create and
 destroy interface



在 2023年02月22日 20:17, Paolo Bonzini 写道:
> On 2/22/23 02:52, Tianrui Zhao wrote:
>>>
>>>> +    vcpu->arch.guest_eentry = (unsigned long)kvm_context->kvm_eentry;
>>>> +    vcpu->arch.vcpu_run = kvm_context->kvm_enter_guest;
>>>> +    vcpu->arch.handle_exit = _kvm_handle_exit;
>>>
>>> Here as well, whatever is constant must not be stored in struct 
>>> kvm_arch_vcpu.
>>>
>>> Paolo
>>
>> Thanks,  we use this in vcpu_arch because the vcpu_arch is used as 
>> argument in switch.S' methods, we can quickly access the guest_eentry 
>> and handle_exit by using the  KVM_ARCH_GEENTRY, KVM_ARCH_HANDLE_EXIT 
>> offsets. If we change to global variable , we should relocate it in 
>> switch.S and may lead  to lower accessing speed.
>
> For guest_eentry and handle_exit this is correct so you can add a 
> comment in kvm_host.h, like
>
>     /* Pointers stored here for easy access from assembly code. */
>
> However, vcpu->arch.vcpu_run is not used in switch.S so there is no 
> need to store it in struct kvm_arch_vcpu.  Since you're already going 
> to move kvm_enter_guest out of kvm_context and into a global variable, 
> please give it the right pointer-to-function type instead of using 
> unsigned long.
>
> Paolo

Thanks, I will remove this vcpu_run and replace it with the new global 
variable, and fix the pointer-to-function type.

Thanks
Tianrui Zhao