2018-08-28 10:39:30

by Thomas Voegtle

Subject: Apollo Lake with newer microcode: not affected by meltdown anymore?

Hello,

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.

This is a Lenovo Ideapad 120S-11IAP with Apollo Lake N3350 (Goldmont)


Thomas

2018-08-28 10:38:31

by Thomas Gleixner

Subject: Re: Apollo Lake with newer microcode: not affected by meltdown anymore?

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

2018-08-28 12:36:49

by Thomas Voegtle

Subject: Re: Apollo Lake with newer microcode: not affected by meltdown anymore?

On Tue, 28 Aug 2018, Thomas Gleixner wrote:

> 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.

Ah, ok.
Didn't think of the most obvious.
But yes RDCL_NO is set to 1 with the new microcode. Wow.

Thanks and sorry for the noise,

Thomas