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