Re: [RFC PATCH v2 14/69] KVM: x86: Split core of hypercall emulation to helper function

[Paolo Bonzini]

On 03/07/21 00:04, isaku.yamahata@xxxxxxxxx wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> By necessity, TDX will use a different register ABI for hypercalls.
> Break out the core functionality so that it may be reused for TDX.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
>   arch/x86/include/asm/kvm_host.h |  4 +++
>   arch/x86/kvm/x86.c              | 55 ++++++++++++++++++++-------------
>   2 files changed, 38 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9c7ced0e3171..80b943e4ab6d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1667,6 +1667,10 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu);
>   void kvm_request_apicv_update(struct kvm *kvm, bool activate,
>   			      unsigned long bit);
>   
> +unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
> +				      unsigned long a0, unsigned long a1,
> +				      unsigned long a2, unsigned long a3,
> +				      int op_64_bit);
>   int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
>   
>   int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d11cf87674f3..795f83a1cf9a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8406,26 +8406,15 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
>   	return;
>   }
>   
> -int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> +unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
> +				      unsigned long a0, unsigned long a1,
> +				      unsigned long a2, unsigned long a3,
> +				      int op_64_bit)
>   {
> -	unsigned long nr, a0, a1, a2, a3, ret;
> -	int op_64_bit;
> -
> -	if (kvm_xen_hypercall_enabled(vcpu->kvm))
> -		return kvm_xen_hypercall(vcpu);
> -
> -	if (kvm_hv_hypercall_enabled(vcpu))
> -		return kvm_hv_hypercall(vcpu);
> -
> -	nr = kvm_rax_read(vcpu);
> -	a0 = kvm_rbx_read(vcpu);
> -	a1 = kvm_rcx_read(vcpu);
> -	a2 = kvm_rdx_read(vcpu);
> -	a3 = kvm_rsi_read(vcpu);
> +	unsigned long ret;
>   
>   	trace_kvm_hypercall(nr, a0, a1, a2, a3);
>   
> -	op_64_bit = is_64_bit_mode(vcpu);
>   	if (!op_64_bit) {
>   		nr &= 0xFFFFFFFF;
>   		a0 &= 0xFFFFFFFF;
> @@ -8434,11 +8423,6 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>   		a3 &= 0xFFFFFFFF;
>   	}
>   
> -	if (static_call(kvm_x86_get_cpl)(vcpu) != 0) {
> -		ret = -KVM_EPERM;
> -		goto out;
> -	}
> -
>   	ret = -KVM_ENOSYS;
>   
>   	switch (nr) {
> @@ -8475,6 +8459,35 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>   		ret = -KVM_ENOSYS;
>   		break;
>   	}
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(__kvm_emulate_hypercall);
> +
> +int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> +{
> +	unsigned long nr, a0, a1, a2, a3, ret;
> +	int op_64_bit;
> +
> +	if (kvm_xen_hypercall_enabled(vcpu->kvm))
> +		return kvm_xen_hypercall(vcpu);
> +
> +	if (kvm_hv_hypercall_enabled(vcpu))
> +		return kvm_hv_hypercall(vcpu);
> +
> +	nr = kvm_rax_read(vcpu);
> +	a0 = kvm_rbx_read(vcpu);
> +	a1 = kvm_rcx_read(vcpu);
> +	a2 = kvm_rdx_read(vcpu);
> +	a3 = kvm_rsi_read(vcpu);
> +
> +	op_64_bit = is_64_bit_mode(vcpu);
> +
> +	if (static_call(kvm_x86_get_cpl)(vcpu) != 0) {
> +		ret = -KVM_EPERM;
> +		goto out;
> +	}
> +
> +	ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit);
>   out:
>   	if (!op_64_bit)
>   		ret = (u32)ret;

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>