Re: [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL

[Jim Mattson]

On Wed, Jan 31, 2018 at 1:42 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:

> Can we just say it sucks to be L2 too? :)  Because in the end as long as
> no one ever writes to spec_ctrl, everybody is happy.

Unfortunately, quite a few OS vendors shipped IBRS-based mitigations
earlier this month. (Has Redhat stopped writing to IA32_SPEC_CTRL yet?
:-)

And in the long run, everyone is going to set IA32_SPEC_CTRL.IBRS=1 on
CPUs with IA32_ARCH_CAPABILITIES.IBRS_ALL.