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SubjectQuery regarding Spectre fixes for qemu-kvm...4.4 LTS Kernel.
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Hi,

I have few queries regarding qemu-kvm support of Spectre related fixes at 4.4.* LTS Kernel.

I see that in upstream kernels, svm_vcpu_run() calls x86_spec_ctrl_set_guest() and x86_spec_ctrl_restore_host().
And calling into x86_virt_spec_ctrl(), that sets IBRS/IBPB/SSBD bits accordingly for guest context.

Related commit IDs below:
commit 5cf687548705412da47c9cec342fd952d71ed3d5
commit ccbcd2674472a978b48c91c1fbfb66c0ff959f24

Looks like this change is not fully ported to 4.4 LTS yet.
x86_spec_ctrl_set_guest() and x86_spec_ctrl_restore_host() interfaces are available, however looks like svm_vcpu_run() is not calling them.
So qemu-kvm running on 4.4 kernels may not have SPEC_CTRL set properly in guest context.

Is there a plan to backport above changes fully into 4.4 LTS kernel?.

Thanks,
Paulose.

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