RE: [PATCH v4 34/34] KVM: x86/vmx: execute "int $2" for NMI reinjection when FRED is enabled

[Li, Xin3]

> > Execute "int $2" for NMI reinjection when FRED is enabled.
> 
> This needs an explanation of _why_.  And as requested earlier[*], please avoid
> "reinjection" in this context.

W/ FRED, we use ERETS to unblock NMI when returning from a NMI handler
(Setting bit 28 of CS).  And there are 2 approaches to do it:
1) "int $2", let the h/w do the job for us.
2) create a FRED stack frame, and then jump to fred_entrypoint_kernel
in arch/x86/entry/entry_64_fred.S.

I prefer "INT $2", what is your opinion?

> [*] https://lore.kernel.org/all/Y20f8v9ObO+IPwU+@xxxxxxxxxx