Re: [PATCH v2] KVM: SVM: Convert plain error code numbers to defines

Sean Christopherson
2024-12-04T00:50:05Z

On Tue, Dec 03, 2024, Melody (Huibo) Wang wrote:
> Hi Sean,
>
> On 12/2/2024 4:11 PM, Sean Christopherson wrote:
>
> >
> > E.g. something like this? Definitely feel free to suggest better names.
> >
> > static inline void svm_vmgexit_set_return_code(struct vcpu_svm *svm,
> > u64 response, u64 data)
> > {
> > ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, response);
> > ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, data);
> > }
> >
> If I make this function more generic where the exit info is set for both KVM
> and the guest, then maybe I can write something like this:

I like the idea, but I actually think it's better to keep the guest and host code
separate in the case, because the guest code should actually set a triple, e.g.

static __always_inline void sev_es_vmgexit_set_exit_info(struct ghcb *ghcb,
u64 exit_code,
u64 exit_info_1,
u64 exit_info_2)
{
ghcb_set_sw_exit_code(ghcb, exit_code);
ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
}

I'm not totally opposed to sharing code, but I think it will be counter-productive
in this specific case. E.g. the guest version needs to be __always_inline so that
it can be used in noinstr code.

> void ghcb_set_exit_info(struct ghcb *ghcb,
> u64 info1, u64 info2)
> {
> ghcb_set_sw_exit_info_1(ghcb, info1);
> ghcb_set_sw_exit_info_2(ghcb, info2);
>
> }
> This way we can address every possible case that sets the exit info - not only KVM.
>
> And I am not sure about the wrappers for each specific case because we will
> have too many, too specific small functions, but if you want them I can add
> them.

I count three. We have far, far more wrappers VMX's is_exception_n(), and IMO
those wrappers make the code significantly more readable.