On 20/02/25 15:16, Xiaoyao Li wrote:
> On 1/29/2025 5:58 PM, Adrian Hunter wrote:
>> +#define TDX_REGS_UNSUPPORTED_SET (BIT(VCPU_EXREG_RFLAGS) | \
>> + BIT(VCPU_EXREG_SEGMENTS))
>> +
>> +fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
>> +{
>> + /*
>> + * force_immediate_exit requires vCPU entering for events injection with
>> + * an immediately exit followed. But The TDX module doesn't guarantee
>> + * entry, it's already possible for KVM to_think_ it completely entry
>> + * to the guest without actually having done so.
>> + * Since KVM never needs to force an immediate exit for TDX, and can't
>> + * do direct injection, just warn on force_immediate_exit.
>> + */
>> + WARN_ON_ONCE(force_immediate_exit);
>> +
>> + trace_kvm_entry(vcpu, force_immediate_exit);
>> +
>> + tdx_vcpu_enter_exit(vcpu);
>> +
>> + vcpu->arch.regs_avail &= ~TDX_REGS_UNSUPPORTED_SET;
>
> I don't understand this. Why only clear RFLAGS and SEGMENTS?
>
> When creating the vcpu, vcpu->arch.regs_avail = ~0 in kvm_arch_vcpu_create().
>
> now it only clears RFLAGS and SEGMENTS for TDX vcpu, which leaves other bits set. But I don't see any code that syncs the guest value of into vcpu->arch.regs[reg].
TDX guest registers are generally not known but
values are placed into vcpu->arch.regs when needed
to work with common code.
We used to use ~VMX_REGS_LAZY_LOAD_SET and tdx_cache_reg()
which has since been removed.
tdx_cache_reg() did not support RFLAGS, SEGMENTS,
EXIT_INFO_1/EXIT_INFO_2 but EXIT_INFO_1/EXIT_INFO_2 became
needed, so that just left RFLAGS, SEGMENTS.
>
>> + trace_kvm_exit(vcpu, KVM_ISA_VMX);
>> +
>> + return EXIT_FASTPATH_NONE;
>> +}
>
