Re: [PATCH v5 09/12] x86/tdx: Wire up KVM hypercalls

[Kuppuswamy, Sathyanarayanan]

On 8/24/21 11:29 AM, Borislav Petkov wrote:
> On Tue, Aug 24, 2021 at 11:11:43AM -0700, Kuppuswamy, Sathyanarayanan wrote:
> > Since TDX code can be used by other hypervisor (non KVM case) we
> > want to have a config to differentiate the KVM related calls.
>
> You need to start explaining yourself better. WTH does "to differentiate
> the KVM related calls" even mean? Differentiate for what?!

tdx_kvm_hypercall() function and its usage in arch/x86/include/asm/kvm_para.h
is only required for KVM hypervisor.

 static inline long kvm_hypercall0(unsigned int nr)
 {
        long ret;
+
+       if (prot_guest_has(PATTR_GUEST_TDX))
+               return tdx_kvm_hypercall(nr, 0, 0, 0, 0);

If the TDX code is complied for another hypervior, we need some config to
disable above the above code. CONFIG_INTEL_TDX_GUEST_KVM is added
for this purpose. If you think there is no sufficient reason, I can
use defined(CONFIG_KVM_GUEST) && defined(CONFIG_INTEL_TDX_GUEST) to protect
the implementation of tdx_kvm_hypercall()


> Our CONFIG space is a huuge mess. Adding another option better be
> properly justified.
>
> > Compiler raised version generation issue for __tdx_hypercall
>
> -ENOTENOUGHINFO.

Following is the error info.

WARNING: modpost: EXPORT symbol "__tdx_hypercall" [vmlinux] version generation failed, symbol will 
not be versioned.

So to fix the above issue, added tdx.h in arch/x86/include/asm/asm-prototypes.h

> Try again.
>
> > Yes. I will fix this in next version.
>
> And here audit all your patchsets. All exports better be _GPL.

Ok. I will check it before my next submission.

>

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer