Re: [PATCH v8 0/8] x86/cpu, kvm: Support AMD Automatic IBRS

Sean Christopherson
2023-01-24T01:19:08Z

On Mon, Jan 23, 2023, Kim Phillips wrote:
> The AMD Zen4 core supports a new feature called Automatic IBRS
> (Indirect Branch Restricted Speculation).
>
> Enable Automatic IBRS by default if the CPU feature is present.
> It typically provides greater performance over the incumbent
> generic retpolines mitigation.
>
> Patch 1 [unchanged from v7] Adds support for the leaf that
> contains the AutoIBRS feature bit.
>
> Patch 2 moves the leaf's open-coded code from __do_cpuid_func()
> to kvm_set_cpu_caps() in preparation for adding the features in
> their native leaf.
>
> Patches 3-6 introduce the new leaf's supported bits one by one.
>
> Patch 7 [unchanged from v7] Adds support for AutoIBRS by turning
> its EFER enablement bit on at startup if the feature is available.
>
> Patch 8 [unchanged from v7] Adds support for propagating AutoIBRS
> to the guest.

A few nits, but otherwise looks good. Thanks!