Comment 11 for bug 1828495

### For the kernel team: This QEMU patchset basically adds 2 new CPU types (IceLake and CascadeLake) support to QEMU (i386/target/{pc,kvm}) AND creates those new CPU mitigations-query features in their structure, allowing QEMU to inform guest which mitigations should be in place for the vCPUs through its own MSRs.

QEMU's

commit f57bceb6ab5163ddd6c41ff4344ab8cf28a9c63d
Author: Robert Hoo <email address hidden>
Date: Mon Oct 15 04:47:23 2018

    kvm: Add support to KVM_GET_MSR_FEATURE_INDEX_LIST and KVM_GET_MSRS system ioctl

    Add kvm_get_supported_feature_msrs() to get supported MSR feature index list.
    Add kvm_arch_get_supported_msr_feature() to get each MSR features value.

    Signed-off-by: Robert Hoo <email address hidden>
    Message-Id: <email address hidden>
    Reviewed-by: Eduardo Habkost <email address hidden>
    Signed-off-by: Eduardo Habkost <email address hidden>

Summarizes the kernel support we need for this "RFE" on Bionic (and higher) QEMUs.

Basically we need support for our ioctl() calls being added here:

kvm_ioctl(s, KVM_GET_MSRS, &msr_data);

kvm_ioctl(s, KVM_GET_MSR_FEATURE_INDEX_LIST, &msr_list);

to be backported to Bionic (and HWE in Bionic) kernels.

With this support, QEMU will be able to query IA32_ARCH_CAPABILITIES MSRs.

More information to this feature can be found:

http://kib.kiev.ua/x86docs/SDMs/336996-002.pdf

Chapter 5 (5.1 - Enumeration by CPUID).

Previous chapters describe briefly the vulnerabilities and how mitigations work HW wise.