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

Isaku Yamahata
2024-07-16T21:19:45Z

On Tue, Jul 09, 2024 at 02:26:35PM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

>
>
> On 4/18/2024 4:10 AM, Isaku Yamahata wrote:
> > On Wed, Apr 17, 2024 at 08:51:39PM +0800,
> > Binbin Wu <binbin.wu@linux.intel.com> wrote:
> >
> > >
> > > 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().
> > You're correct. This comment is stale and should be removed it.
> Also, since the tdx_complete_pio_out() is installed as complete_userspace_io
> callback for write, it's more reasonable to move the reset of pio.count into
> tdx_complete_pio_out().
> How about the following fixup:

It makes sense. It matches better with other complete callbacks
for tdx_complete_pio_out() to clear pio.count to 0.

> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 9ead46cb75ab..b43bb8ccddb9 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1115,6 +1115,7 @@ static int tdx_emulate_hlt(struct kvm_vcpu *vcpu)
>
>  static int tdx_complete_pio_out(struct kvm_vcpu *vcpu)
>  {
> +       vcpu->arch.pio.count = 0;
>         tdvmcall_set_return_code(vcpu, TDVMCALL_SUCCESS);
>         tdvmcall_set_return_val(vcpu, 0);
>         return 1;
> @@ -1159,15 +1160,13 @@ static int tdx_emulate_io(struct kvm_vcpu *vcpu)
>         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
> +       } else {
>                 ret = ctxt->ops->pio_in_emulated(ctxt, size, port, &val, 1);
> +       }
>
> -       if (ret)
> +       if (ret) {
>                 tdvmcall_set_return_val(vcpu, val);
> -       else {
> +       } else {
>                 if (write)
>                         vcpu->arch.complete_userspace_io =
> tdx_complete_pio_out;
>                 else
>
>

--
Isaku Yamahata <isaku.yamahata@intel.com>