Re: [PATCH v2 07/58] i386/tdx: Introduce is_tdx_vm() helper and cache tdx_guest object

[Xiaoyao Li]

On 8/21/2023 4:48 PM, Daniel P. Berrangé wrote:
> On Fri, Aug 18, 2023 at 05:49:50AM -0400, Xiaoyao Li wrote:
> > It will need special handling for TDX VMs all around the QEMU.
> > Introduce is_tdx_vm() helper to query if it's a TDX VM.
> >
> > Cache tdx_guest object thus no need to cast from ms->cgs every time.
> >
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> > ---
> >   target/i386/kvm/tdx.c | 13 +++++++++++++
> >   target/i386/kvm/tdx.h | 10 ++++++++++
> >   2 files changed, 23 insertions(+)
> >
> > diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> > index 255c47a2a553..56cb826f6125 100644
> > --- a/target/i386/kvm/tdx.c
> > +++ b/target/i386/kvm/tdx.c
> > @@ -21,8 +21,16 @@
> >   #include "kvm_i386.h"
> >   #include "tdx.h"
> >   
> > +static TdxGuest *tdx_guest;
> > +
> >   static struct kvm_tdx_capabilities *tdx_caps;
> >   
> > +/* It's valid after kvm_confidential_guest_init()->kvm_tdx_init() */
> > +bool is_tdx_vm(void)
> > +{
> > +    return !!tdx_guest;
> > +}
> > +
> >   enum tdx_ioctl_level{
> >       TDX_PLATFORM_IOCTL,
> >       TDX_VM_IOCTL,
> > @@ -109,10 +117,15 @@ static void get_tdx_capabilities(void)
> >   
> >   int tdx_kvm_init(MachineState *ms, Error **errp)
> >   {
> > +    TdxGuest *tdx = (TdxGuest *)object_dynamic_cast(OBJECT(ms->cgs),
> > +                                                    TYPE_TDX_GUEST);
>
> This method can return NULL.  Presumably tdx_kvm_init() should only
> be called if we already checked  ms->cgs == TYPE_TDX_GUEST. If so
> then use object_dynamic_cast_assert() instead.

object_dynamic_cast_assert() is for OBJECT_CHECK() and INTERFACE_CHECK().

So I will use TDX_GUEST(OBJECT(ms->cgs)) (introduced in patch 2) 
instead, which is the wrapper of OBJECT_CHECK().