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    Subject[PATCH 5.6 138/254] KVM: VMX: fix crash cleanup when KVM wasnt used
    Date
    From: Vitaly Kuznetsov <vkuznets@redhat.com>

    commit dbef2808af6c594922fe32833b30f55f35e9da6d upstream.

    If KVM wasn't used at all before we crash the cleanup procedure fails with
    BUG: unable to handle page fault for address: ffffffffffffffc8
    #PF: supervisor read access in kernel mode
    #PF: error_code(0x0000) - not-present page
    PGD 23215067 P4D 23215067 PUD 23217067 PMD 0
    Oops: 0000 [#8] SMP PTI
    CPU: 0 PID: 3542 Comm: bash Kdump: loaded Tainted: G D 5.6.0-rc2+ #823
    RIP: 0010:crash_vmclear_local_loaded_vmcss.cold+0x19/0x51 [kvm_intel]

    The root cause is that loaded_vmcss_on_cpu list is not yet initialized,
    we initialize it in hardware_enable() but this only happens when we start
    a VM.

    Previously, we used to have a bitmap with enabled CPUs and that was
    preventing [masking] the issue.

    Initialized loaded_vmcss_on_cpu list earlier, right before we assign
    crash_vmclear_loaded_vmcss pointer. blocked_vcpu_on_cpu list and
    blocked_vcpu_on_cpu_lock are moved altogether for consistency.

    Fixes: 31603d4fc2bb ("KVM: VMX: Always VMCLEAR in-use VMCSes during crash with kexec support")
    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    Message-Id: <20200401081348.1345307-1-vkuznets@redhat.com>
    Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kvm/vmx/vmx.c | 12 +++++++-----
    1 file changed, 7 insertions(+), 5 deletions(-)

    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -2264,10 +2264,6 @@ static int hardware_enable(void)
    !hv_get_vp_assist_page(cpu))
    return -EFAULT;

    - INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
    - INIT_LIST_HEAD(&per_cpu(blocked_vcpu_on_cpu, cpu));
    - spin_lock_init(&per_cpu(blocked_vcpu_on_cpu_lock, cpu));
    -
    kvm_cpu_vmxon(phys_addr);
    if (enable_ept)
    ept_sync_global();
    @@ -8025,7 +8021,7 @@ module_exit(vmx_exit);

    static int __init vmx_init(void)
    {
    - int r;
    + int r, cpu;

    #if IS_ENABLED(CONFIG_HYPERV)
    /*
    @@ -8079,6 +8075,12 @@ static int __init vmx_init(void)
    return r;
    }

    + for_each_possible_cpu(cpu) {
    + INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
    + INIT_LIST_HEAD(&per_cpu(blocked_vcpu_on_cpu, cpu));
    + spin_lock_init(&per_cpu(blocked_vcpu_on_cpu_lock, cpu));
    + }
    +
    #ifdef CONFIG_KEXEC_CORE
    rcu_assign_pointer(crash_vmclear_loaded_vmcss,
    crash_vmclear_local_loaded_vmcss);

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