Re: [RFC PATCH v5 102/104] KVM: TDX: Add methods to ignore accesses to CPU state

[Xiaoyao Li]

On 4/12/2022 2:52 PM, Paolo Bonzini wrote:
> On 4/12/22 08:49, Xiaoyao Li wrote:
> > > +void tdx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
> > > +{
> > > +    kvm_register_mark_available(vcpu, reg);
> > > +    switch (reg) {
> > > +    case VCPU_REGS_RSP:
> > > +    case VCPU_REGS_RIP:
> > > +    case VCPU_EXREG_PDPTR:
> > > +    case VCPU_EXREG_CR0:
> > > +    case VCPU_EXREG_CR3:
> > > +    case VCPU_EXREG_CR4:
> > > +        break;
> > > +    default:
> > > +        KVM_BUG_ON(1, vcpu->kvm);
> > > +        break;
> > > +    }
> > > +}
> >
> > Isaku,
> >
> > We missed one case that some GPRs are accessible by KVM/userspace for 
> > TDVMCALL exit.
>
> If a register is not in the VMX_REGS_LAZY_LOAD_SET it will never be 
> passed to tdx_cache_reg.  As far as I understand those TDVMCALL 
> registers do not include either RSP or RIP.

Sorry, I should not keep the code snippet of tdx_cache_reg() as 
reference to mislead you and other people.

I just want to remind that in the certain case of TDVMCALL, GPRs might 
be accessible.

> Paolo