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Date:   Tue, 28 Aug 2018 12:37:02 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Thomas Voegtle <tv@lio96.de>
cc:     x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Dave Hansen <dave.hansen@intel.com>
Subject: Re: Apollo Lake with newer microcode: not affected by meltdown
 anymore?
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On Tue, 28 Aug 2018, Thomas Voegtle wrote:
> Kernel 4.18.5 with old microcode:
> 
> [    0.000000] microcode: microcode updated early to revision 0x2c, date =
> 2017-03-25
> cat /sys/devices/system/cpu/vulnerabilities/meltdown
> Mitigation: PTI
> 
> 
> Kernel 4.18.5 with new microcode (microcode-20180807.tgz), same config:
> 
> [    0.000000] microcode: microcode updated early to revision 0x32, date =
> 2018-05-11
> cat /sys/devices/system/cpu/vulnerabilities/meltdown
> Not affected
> 
> 
> This happens with 4.14.y and 4.9.y as well.
> 
> The same with ssb:
> old microcode: spec_store_bypass:Vulnerable
> new microcode: spec_store_bypass:Not affected
> 
> Is this intentional behavior? I have never seen this on other CPUs, such
> as Gemini Lake or Baytrail, Haswell etc.

Looks like the micro code update has the relevant bits set in the
IA32_ARCH_CAPABILITIES MSR, which tell the kernel that the CPU is not
vulnerable. So it seems Intel was able to mitigate the mess in micro code
for this particular CPU model.

Thanks,

	tglx