On Wed, Sep 13 2023 at 21:48, Xin Li wrote: > +static inline void fred_syscall_init(void) > +{ > + /* > + * Per FRED spec 5.0, FRED uses the ring 3 FRED entrypoint for SYSCALL > + * and SYSENTER, and ERETU is the only legit instruction to return to > + * ring 3, as a result there is _no_ need to setup the SYSCALL and > + * SYSENTER MSRs. > + * > + * Note, both sysexit and sysret cause #UD when FRED is enabled. > + */ > + wrmsrl(MSR_LSTAR, 0ULL); > + wrmsrl_cstar(0ULL);
That write is pointless. See the comment in wrmsrl_cstar(). Thanks, tglx