Re: [PATCH 0/2] KVM: x86: Propagate AMD-specific IBRS bits to guests

[Borislav Petkov]

On Mon, Feb 27, 2023 at 09:05:24PM +0000, Takahiro Itazuri wrote:
> VMMs retrieve supported CPUID features via KVM_GET_SUPPORTED_CPUID to
> construct CPUID information to be passed to KVM_SET_CPUID2. Most CPUID
> feature bits related to speculative attacks are propagated from host
> CPUID. But AMD processors have AMD-specific IBRS related bits in CPUID
> Fn8000_0008_EBX (ref: AMD64 Architecture Programmer's Manual Volume 3:
> General-Purpose and System Instructions) and some bits are not
> propagated to guests.
> 
> Enable propagation of these bits to guests, so that VMMs don't have to
> enable them explicitly based on host CPUID.

How hard is it for the VMMs to enable them?

-- 
Regards/Gruss,
    Boris.

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