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

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Message-ID: <8ab7565c-df06-b5a5-d02d-899ba976414b@redhat.com>
Date:   Tue, 5 Nov 2019 11:41:49 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     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:     Xiaoyao Li <xiaoyao.li@...el.com>, 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 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.

How is the bug reproducible?

Paolo