linux-kernel - Re: [PATCH v2 04/23] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED

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Date:   Mon, 20 Dec 2021 14:20:05 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jing Liu <jing2.liu@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com
Cc:     seanjc@...gle.com, jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, guang.zeng@...el.com,
        wei.w.wang@...el.com, yang.zhong@...el.com
Subject: Re: [PATCH v2 04/23] kvm: x86: Exclude unpermitted xfeatures at
 KVM_GET_SUPPORTED_CPUID

On 12/17/21 16:29, Jing Liu wrote:
>   
> +Permissions must be set via prctl() for dynamically-enabled XSAVE
> +features before calling this ioctl. Otherwise those feature bits are
> +excluded.
> +

Dynamically-enabled feature bits need to be requested with 
``arch_prctl()`` before calling this ioctl.  Feature bits that have not 
been requested are excluded from the result.

Thanks,

Paolo