[libvirt] [PATCH] cpu: add 'amd-ssbd' and 'amd-no-ssb' CPU features (CVE-2018-3639)

[Kashyap Chamarthy]

On Thu, Jun 14, 2018 at 11:48:41AM +0100, Daniel P. Berrangé wrote:

[...]

> Note that neither amd-ssbd or amd-no-ssb will be reported by the kernel
> in /proc/cpuinfo. It knows about these CPUID bits and does the right thing,
> but doesn't report their existance as distinct flags in /proc/cpuinfo.

Since it isn't pushed yet, minor nit-pick: s/existance/existence/

Should the commit message be amended to mention that `/proc/cpuinfo`
will, confusingly enough, report 'ssbd' (for 'amd-ssbd')?

Because reading this thread on 'qemu-devel':

    https://lists.nongnu.org/archive/html/qemu-devel/2018-06/msg03660.html
    [PATCH 1/2] i386: define the AMD 'amd-ssbd' CPUID feature bit

Says:

[quote]
    It [kernel] will only report 'ssbd' but not 'amd-ssb-no' nor
    'amd-ssbd'.

    [...]

    The code that finds the AMD_SSBD and sets the 'ssbd' is:
    
    +       if (cpu_has(c, X86_FEATURE_AMD_SSBD)) {
    +               set_cpu_cap(c, X86_FEATURE_SSBD);
    +               set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL);
    +               clear_cpu_cap(c, X86_FEATURE_VIRT_SSBD);
    +       }
    
    Meaning the 'ssbd' will show up in /proc/cpuinfo 
[/quote]

[...]

-- 
/kashyap