Re: [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode reload

Greg KH
2018-01-05T13:32:14Z

On Thu, Jan 04, 2018 at 07:50:33PM +0100, Borislav Petkov wrote:
> On Thu, Jan 04, 2018 at 07:34:30PM +0100, Andrea Arcangeli wrote:
> > void spec_ctrl_rescan_cpuid(void)
> > {
> > int cpu;
> >
> > if (use_ibp_disable)
> > return;
> > mutex_lock(&spec_ctrl_mutex);
> > if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL ||
> > boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
> > /* detect spec ctrl related cpuid additions */
> > init_scattered_cpuid_features(&boot_cpu_data);
>
> You don't need to noodle through all the scattered features - just the
> two bits.

Does it really matter? Rescanning everything can't hurt here, and it
shouldn't be noticable in any boot time chart. I feel like arguing
about tiny stuff like this takes away from the obvious other problems
this whole patch series had :(

But hey, I'm guilty of it numerous times as well, I know, so I'll shut
up now...

thanks,

greg k-h