On Fri, Nov 14, 2025, Michael Kelley wrote:
> From: Sean Christopherson <[email protected]> Sent: Thursday, November 13,
> 2025 2:56 PM
> >
>
> Adding Microsoft's Nuno Das Neves to the "To:" line since he
> originated the work to keep the Linux headers such as hvgdk.h in
> sync with the Windows counterparts from which they originate.
...
> > /* Exit code reserved for hypervisor/software use */
> > -#define SVM_EXIT_SW 0xf0000000
> > +#define SVM_EXIT_SW 0xf0000000ull
> >
> > -#define SVM_EXIT_ERR -1
> > +#define SVM_EXIT_ERR -1ull
> >
>
> [snip]
>
> > diff --git a/include/hyperv/hvgdk.h b/include/hyperv/hvgdk.h
> > index dd6d4939ea29..56b695873a72 100644
> > --- a/include/hyperv/hvgdk.h
> > +++ b/include/hyperv/hvgdk.h
> > @@ -281,7 +281,7 @@ struct hv_vmcb_enlightenments {
> > #define HV_VMCB_NESTED_ENLIGHTENMENTS 31
> >
> > /* Synthetic VM-Exit */
> > -#define HV_SVM_EXITCODE_ENL 0xf0000000
> > +#define HV_SVM_EXITCODE_ENL 0xf0000000u
>
> Is there a reason for making this Hyper-V code just "u", while
> making the SVM_VMGEXIT_* values "ull"? I don't think
> "u" vs. "ull" shouldn't make any difference when assigning to a
> u64, but the inconsistency piqued my interest ....
I hedged and went for a more "minimal" change because it isn't KVM code, and at
the time because I thought the value isn't defined by the APM. Though looking
again at the APM, it does reserve that value for software
F000_000h Unused Reserved for Host.
and I can't find anything in the TLFS. Ah, my PDF copy is just stale, it's
indeed
defined as a synthetic exit.
https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/nested-virtualization#synthetic-vm-exit
Anyways, I'm in favor of making HV_SVM_EXITCODE_ENL an ull, though part of me
wonders if we should do:
#define HV_SVM_EXITCODE_ENL SVM_EXIT_SW
