Re: [PATCH 01/13] x86/microcode/intel: Drop stashed AP patch pointer optimization

[Thomas Gleixner]

On Tue, 17 Jan 2017, Borislav Petkov wrote:

> From: Borislav Petkov <bp@xxxxxxx>
> 
> This was meant to save us the scanning of the microcode containter in
> the initrd since the first AP had already done that but it can also hurt
> us:
> 
> Imagine a single hyperthreaded CPU (Intel(R) Atom(TM) CPU N270 for
> example) which updates the microcode on the BSP but since the microcode
> engine is shared between the two threads, the update on CPU1 doesn't
> happen because it has already happened on CPU0 and we don't find a newer
> microcode revision.
> 
> Which doesn't set the intel_ucode_patch pointer and at initrd
> jettisoning time and we don't save the microcode patch for later
> application.
> 
> Now, when we suspend to RAM, the loaded microcode gets cleared so we
> need to reload but there's no patch saved in the cache.
> 
> Removing this optimization fixes this issue and all is fine and dandy.
> 
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>

So this one needs to go into x86/urgent

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>