linux-kernel - Re: [PATCH] KVM: X86: Dynamically allocating MSR number lists(msrs_to_save[], emulated_msrs[], msr_based

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Message-ID: <75a63a8d-6d80-7749-a5c7-da7a43c2f53c@redhat.com>
Date:   Tue, 5 Nov 2019 12:20:37 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Chenyi Qiang <chenyi.qiang@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] KVM: X86: Dynamically allocating MSR number
 lists(msrs_to_save[], emulated_msrs[], msr_based_features[])

On 05/11/19 12:11, Xiaoyao Li wrote:
> On 11/5/2019 6:41 PM, Paolo Bonzini wrote:
>> On 05/11/19 10:20, Chenyi Qiang wrote:
>>> The three msr number lists(msrs_to_save[], emulated_msrs[] and
>>> msr_based_features[]) are global arrays of kvm.ko, which are
>>> initialized/adjusted (copy supported MSRs forward to override the
>>> unsupported MSRs) when installing kvm-{intel,amd}.ko, but it doesn't
>>> reset these three arrays to their initial value when uninstalling
>>> kvm-{intel,amd}.ko. Thus, at the next installation, kvm-{intel,amd}.ko
>>> will initialize the modified arrays with some MSRs lost and some MSRs
>>> duplicated.
>>>
>>> So allocate and initialize these three MSR number lists dynamically when
>>> installing kvm-{intel,amd}.ko and free them when uninstalling.
>>
>> I don't understand.  Do you mean insmod/rmmod when you say
>> installing/uninstalling? Global data must be reloaded from the ELF file
>> when insmod is executed.
> 
> Yes, we mean insmod/rmmod.
> The problem is that these three MSR arrays belong to kvm.ko but not
> kvm-{intel,amd}.ko. When we rmmod kvm_intel.ko, it does nothing to them.

Ok, thanks for the explanation.

Paolo