[RFC PATCH 01/25] KVM: arm64: Add has_reset_once flag for vcpu

[Andrew Jones]

On Mon, Oct 11, 2021 at 09:35:11PM -0700, Reiji Watanabe wrote:
> Introduce 'has_reset_once' flag in kvm_vcpu_arch, which indicates
> if the vCPU reset has been done once, for later use.
> 
> Signed-off-by: Reiji Watanabe <reijiw at google.com>
> ---
>  arch/arm64/include/asm/kvm_host.h | 2 ++
>  arch/arm64/kvm/reset.c            | 4 ++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index f8be56d5342b..9b5e7a3b6011 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -384,6 +384,7 @@ struct kvm_vcpu_arch {
>  		u64 last_steal;
>  		gpa_t base;
>  	} steal;
> +	bool has_reset_once;
>  };
>  
>  /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
> @@ -449,6 +450,7 @@ struct kvm_vcpu_arch {
>  
>  #define vcpu_has_sve(vcpu) (system_supports_sve() &&			\
>  			    ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE))
> +#define	vcpu_has_reset_once(vcpu) ((vcpu)->arch.has_reset_once)
>  
>  #ifdef CONFIG_ARM64_PTR_AUTH
>  #define vcpu_has_ptrauth(vcpu)						\
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 5ce36b0a3343..4d34e5c1586c 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -305,6 +305,10 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>  	if (loaded)
>  		kvm_arch_vcpu_load(vcpu, smp_processor_id());
>  	preempt_enable();
> +
> +	if (!ret && !vcpu->arch.has_reset_once)
> +		vcpu->arch.has_reset_once = true;
> +
>  	return ret;
>  }
>  
> -- 
> 2.33.0.882.g93a45727a2-goog
>

Hi Reiji,

Can't we use kvm_vcpu_initialized(vcpu)? vcpu->arch.target should
only be >= when we've successfully reset the vcpu at least once.

Thanks,
drew