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SubjectRe: [PATCH v2 06/29] LoongArch: KVM: Implement vcpu create and destroy interface
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

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