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    SubjectRe: [PATCH v19 109/130] KVM: TDX: Handle TDX PV port io hypercall
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    On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > Wire up TDX PV port IO hypercall to the KVM backend function.
    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
    > ---
    > 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;
    > }


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