linux-kernel - Re: [PATCH v3 3/4] KVM: VMX: Emulate MSR_IA32_ARCH

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Date:   Tue, 30 Jan 2018 18:21:47 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     KarimAllah Ahmed <karahmed@...zon.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        KarimAllah Ahmed <karahmed@...zon.de>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        Asit Mallick <asit.k.mallick@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH v3 3/4] KVM: VMX: Emulate MSR_IA32_ARCH_CAPABILITIES

On 29/01/2018 19:25, KarimAllah Ahmed wrote:
>>> +    case MSR_IA32_ARCH_CAPABILITIES:
>>> +        if (!msr_info->host_initiated)
>>> +            return 1;
>>> +        vmx->arch_capabilities = data;
>>> +        break;
>>
>> arch capabilities is read only. You don't need the set_msr handling
>> for this.
> 
> This is only for host driven writes. This would allow QEMU/whatever to
> override the default value (i.e. the value from the hardware).

Agreed.

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>