Re: intel CPU vulnerability NO_SSB whitelist for AIRMONT

[Pawan Gupta]

On Tue, Jul 09, 2024 at 01:21:44PM +0530, Shanavas.K.S wrote:
> Hi All,
> This is in reference to
> https://github.com/torvalds/linux/blame/master/arch/x86/kernel/cpu/common.c#L1169.
> The whitelist for INTEL_ATOM_AIRMONT has NO_SSB enabled  which means
> cache speculation vulnerability(spectre 4,CVE-2018-3639) is not
> applicable to  this processor. But NO_SSB is not set for
> INTEL_ATOM_AIRMONT_NP and INTEL_ATOM_AIRMONT_MID. Are these settings
> missing for AIRMONT_NP and AIRMONT_MID or is there a real difference
> between cache speculation between these processors?

I believe they were released much later than AIRMONT and hence should be
enumerating MSR IA32_ARCH_CAPABILITIES[SSB_NO](bit 4). If you have these
system, is bit 4 not set?

If it is set there is no need to explicitly add NO_SSB to the table.