On Fri, Oct 09, 2020 at 12:42:53PM -0700, ira.weiny@xxxxxxxxx wrote: > @@ -644,6 +663,8 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p) > > if ((tifp ^ tifn) & _TIF_SLD) > switch_to_sld(tifn); > + > + pks_sched_in(); > } > You seem to have lost the comment proposed here: https://lkml.kernel.org/r/20200717083140.GW10769@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx It is useful and important information that the wrmsr normally doesn't happen. > diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c > index 3cf8f775f36d..30f65dd3d0c5 100644 > --- a/arch/x86/mm/pkeys.c > +++ b/arch/x86/mm/pkeys.c > @@ -229,3 +229,31 @@ u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags) > > return pk_reg; > } > + > +DEFINE_PER_CPU(u32, pkrs_cache); > + > +/** > + * It should also be noted that the underlying WRMSR(MSR_IA32_PKRS) is not > + * serializing but still maintains ordering properties similar to WRPKRU. > + * The current SDM section on PKRS needs updating but should be the same as > + * that of WRPKRU. So to quote from the WRPKRU text: > + * > + * WRPKRU will never execute transiently. Memory accesses > + * affected by PKRU register will not execute (even transiently) > + * until all prior executions of WRPKRU have completed execution > + * and updated the PKRU register. (whitespace damage; space followed by tabstop) > + */ > +void write_pkrs(u32 new_pkrs) > +{ > + u32 *pkrs; > + > + if (!static_cpu_has(X86_FEATURE_PKS)) > + return; > + > + pkrs = get_cpu_ptr(&pkrs_cache); > + if (*pkrs != new_pkrs) { > + *pkrs = new_pkrs; > + wrmsrl(MSR_IA32_PKRS, new_pkrs); > + } > + put_cpu_ptr(pkrs); > +} looks familiar that... :-)
