Applied: [Xenial][PATCH 0/1] x86_max_cores==0 panic on Xen guests

[Kamal Mostafa]

Applied to xenial/master-next.


On Wed, Mar 28, 2018 at 09:28:16AM -0700, Kamal Mostafa wrote:
> BugLink: http://bugs.launchpad.net/bugs/1758869
> 
> == SRU ==
> Fix "Kernel panic with AWS 4.4.0-1053 / 4.4.0-1015".
> Boot-time panic occurs on all c3.large instances, due to a recently
> introduced* divide-by-zero which occurs when x86_max_cores contains 0
> as is the case in some Xen guest configurations as indicated by this
> pre-existing dmesg indicator: "smpboot: x86_max_cores == zero !?!?"
> 
> *The divide-by-zero was introduced by mainline commit:
> 7e702d1 x86/microcode/intel: Extend BDW late-loading further with LLC size check
> 
> and fixed (reference https://lkml.org/lkml/2018/2/6/320) by:
> a15a753 x86/microcode/AMD: Do not load when running on a hypervisor
> 
> This fix patch is currently pending for cc: stable.
> 
> == Fix ==
> Simple context backport from mainline short circuits code paths through
> pre-microcode-loading system checks which are pointless on the guest anyway
> since it won't load microcode.  Low regression potential.
> 
> Borislav Petkov (1):
>   x86/microcode/AMD: Do not load when running on a hypervisor
> 
>  arch/x86/kernel/cpu/microcode/core.c | 28 +++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)
> 
> -- 
> 2.7.4
> 
> 
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