Re: [patch V9 00/16] SSB

[Thomas Gleixner <tglx@linutronix.de>]

On Tue, 1 May 2018, speck for Tim Chen wrote:
> I used the fix below to take care of Intel CPU. The fix also works for
> CPU taken offline and back online.  AMD cpu has the proper setting
> of their MSR in boot up via identify_secondary_cpu's call to
> x86_setup_ap_spec_ctrl.
> 
> void x86_setup_ap_spec_ctrl(void)
> {
>         if (boot_cpu_has(X86_FEATURE_IBRS))
>                 x86_set_spec_ctrl(x86_spec_ctrl_base & ~x86_spec_ctrl_mask);
> 
>         if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
>                 x86_amd_rds_enable();
> }
> 
> But AMD cpu may have issue when CPU is brought offline and back online as
> x86_setup_ap_spec_ctrl may not get called then.

AMD has no issue at all neither has Intel. On both x86_setup_ap_spec_ctrl()
is called everytime a CPU comes online, whether it's boot or after a
offline/online sequence.

start_secondary()
  smp_callin()
    identify_secondary_cpu()
      x86_setup_ap_spec_ctrl()

Care to read the code before making uneducated claims?

Thanks,

	tglx