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

["Daniel P. Berrangé" <berrange@redhat.com>]

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.

> +
>      if (!tdx_caps) {
>          get_tdx_capabilities();
>      }
>  
> +    tdx_guest = tdx;
> +
>      return 0;
>  }
>  
> diff --git a/target/i386/kvm/tdx.h b/target/i386/kvm/tdx.h
> index c8a23d95258d..4036ca2f3f99 100644
> --- a/target/i386/kvm/tdx.h
> +++ b/target/i386/kvm/tdx.h
> @@ -1,6 +1,10 @@
>  #ifndef QEMU_I386_TDX_H
>  #define QEMU_I386_TDX_H
>  
> +#ifndef CONFIG_USER_ONLY
> +#include CONFIG_DEVICES /* CONFIG_TDX */
> +#endif
> +
>  #include "exec/confidential-guest-support.h"
>  
>  #define TYPE_TDX_GUEST "tdx-guest"
> @@ -16,6 +20,12 @@ typedef struct TdxGuest {
>      uint64_t attributes;    /* TD attributes */
>  } TdxGuest;
>  
> +#ifdef CONFIG_TDX
> +bool is_tdx_vm(void);
> +#else
> +#define is_tdx_vm() 0
> +#endif /* CONFIG_TDX */
> +
>  int tdx_kvm_init(MachineState *ms, Error **errp);
>  
>  #endif /* QEMU_I386_TDX_H */
> -- 
> 2.34.1
> 

With regards,
Daniel
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