Re: [PATCH v19 109/130] KVM: TDX: Handle TDX PV port io hypercall

[Binbin Wu]

On 2/26/2024 4:26 PM, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Wire up TDX PV port IO hypercall to the KVM backend function.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> v18:
> - Fix out case to set R10 and R11 correctly when user space handled port
>    out.
> ---
>   arch/x86/kvm/vmx/tdx.c | 67 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 67 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index a2caf2ae838c..55fc6cc6c816 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1152,6 +1152,71 @@ static int tdx_emulate_hlt(struct kvm_vcpu *vcpu)
>   	return kvm_emulate_halt_noskip(vcpu);
>   }
>   
> +static int tdx_complete_pio_out(struct kvm_vcpu *vcpu)
> +{
> +	tdvmcall_set_return_code(vcpu, TDVMCALL_SUCCESS);
> +	tdvmcall_set_return_val(vcpu, 0);
> +	return 1;
> +}
> +
> +static int tdx_complete_pio_in(struct kvm_vcpu *vcpu)
> +{
> +	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
> +	unsigned long val = 0;
> +	int ret;
> +
> +	WARN_ON_ONCE(vcpu->arch.pio.count != 1);
> +
> +	ret = ctxt->ops->pio_in_emulated(ctxt, vcpu->arch.pio.size,
> +					 vcpu->arch.pio.port, &val, 1);
> +	WARN_ON_ONCE(!ret);
> +
> +	tdvmcall_set_return_code(vcpu, TDVMCALL_SUCCESS);
> +	tdvmcall_set_return_val(vcpu, val);
> +
> +	return 1;
> +}
> +
> +static int tdx_emulate_io(struct kvm_vcpu *vcpu)
> +{
> +	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
> +	unsigned long val = 0;
> +	unsigned int port;
> +	int size, ret;
> +	bool write;
> +
> +	++vcpu->stat.io_exits;
> +
> +	size = tdvmcall_a0_read(vcpu);
> +	write = tdvmcall_a1_read(vcpu);
> +	port = tdvmcall_a2_read(vcpu);
> +
> +	if (size != 1 && size != 2 && size != 4) {
> +		tdvmcall_set_return_code(vcpu, TDVMCALL_INVALID_OPERAND);
> +		return 1;
> +	}
> +
> +	if (write) {
> +		val = tdvmcall_a3_read(vcpu);
> +		ret = ctxt->ops->pio_out_emulated(ctxt, size, port, &val, 1);
> +
> +		/* No need for a complete_userspace_io callback. */
I am confused about the comment.

The code below sets the complete_userspace_io callback for write case,
i.e. tdx_complete_pio_out().

> +		vcpu->arch.pio.count = 0;
> +	} else
> +		ret = ctxt->ops->pio_in_emulated(ctxt, size, port, &val, 1);
> +
> +	if (ret)
> +		tdvmcall_set_return_val(vcpu, val);
> +	else {
> +		if (write)
> +			vcpu->arch.complete_userspace_io = tdx_complete_pio_out;
> +		else
> +			vcpu->arch.complete_userspace_io = tdx_complete_pio_in;
> +	}
> +
> +	return ret;
> +}
> +
>   static int handle_tdvmcall(struct kvm_vcpu *vcpu)
>   {
>   	if (tdvmcall_exit_type(vcpu))
> @@ -1162,6 +1227,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
>   		return tdx_emulate_cpuid(vcpu);
>   	case EXIT_REASON_HLT:
>   		return tdx_emulate_hlt(vcpu);
> +	case EXIT_REASON_IO_INSTRUCTION:
> +		return tdx_emulate_io(vcpu);
>   	default:
>   		break;
>   	}