On Tue, Nov 7, 2023 at 6:58 AM <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>
> ---
> arch/x86/kvm/vmx/tdx.c | 57 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 57 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 4e48989d364f..d4b09255ad32 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1140,6 +1140,61 @@ static int tdx_emulate_hlt(struct kvm_vcpu *vcpu)
> return kvm_emulate_halt_noskip(vcpu);
> }
>
> +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, TDG_VP_VMCALL_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, TDG_VP_VMCALL_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. */
> + vcpu->arch.pio.count = 0;
> + } else {
> + ret = ctxt->ops->pio_in_emulated(ctxt, size, port, &val, 1);
> + if (!ret)
> + vcpu->arch.complete_userspace_io = tdx_complete_pio_in;
> + else
> + tdvmcall_set_return_val(vcpu, val);
> + }
> + if (ret)
> + tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
In the case of a write operation that needs to exit to userspace,
pio_out_emulated is going to return 0 which means that the return code
is never set by tdx_emulate_io.
The reason this code is working now is because r10 is already set to 0
by the guest as part of the call to tdvmcall and never gets written by
the host.
> + return ret;
> +}
> +
> static int handle_tdvmcall(struct kvm_vcpu *vcpu)
> {
> if (tdvmcall_exit_type(vcpu))
> @@ -1150,6 +1205,8 @@ 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;
> }
> --
> 2.25.1
>
