KVM: VMX: fix crash cleanup when KVM wasn't used

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>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 8ed78b5287a3ae0ca4abb2bb777b0f01bfdf3e27..5c85de08dc948198316ff42b6ef9771223b442a2 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2232,10 +2232,6 @@ 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));
-
        rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
 
        test_bits = FEATURE_CONTROL_LOCKED;
@@ -8006,7 +8002,7 @@ module_exit(vmx_exit);
 
 static int __init vmx_init(void)
 {
-       int r;
+       int r, cpu;
 
 #if IS_ENABLED(CONFIG_HYPERV)
        /*
@@ -8060,6 +8056,12 @@ 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);