Re: [PATCH] target/i386: SEV: do not assume machine->cgs is SEV

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 6/6/2024 6:44 AM, Paolo Bonzini wrote:
> There can be other confidential computing classes that are not derived
> from sev-common.  Avoid aborting when encountering them.

I hit it today when rebasing TDX patches to latest QEMU master, which 
has the SEV-SNP series merged. (I didn't get time to review it between 
it gets merged.)

> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   target/i386/sev.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index 004c667ac14..97e15f8b7a9 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -1710,7 +1710,9 @@ void sev_es_set_reset_vector(CPUState *cpu)

my approach is to guard with sev_enabled() when calling 
sev_es_set_reset_vector() in kvm_arch_reset_vcpu(), because calling sev* 
specific function in generic kvm code doesn't look reasonable to me.

>   {
>       X86CPU *x86;
>       CPUX86State *env;
> -    SevCommonState *sev_common = SEV_COMMON(MACHINE(qdev_get_machine())->cgs);
> +    ConfidentialGuestSupport *cgs = MACHINE(qdev_get_machine())->cgs;
> +    SevCommonState *sev_common = SEV_COMMON(
> +        object_dynamic_cast(OBJECT(cgs), TYPE_SEV_COMMON));
>   
>       /* Only update if we have valid reset information */
>       if (!sev_common || !sev_common->reset_data_valid) {