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.c b/arch/x86/kvm/vmx.c
index 5e76ff10f7f5dd0c8b829726f07b13be021e5a85..f8e3f3c48283ac1e82efae5e3e4a0afdcfb08bb1 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3776,10 +3776,6 @@ static int hardware_enable(void)
        if (cr4_read_shadow() & X86_CR4_VMXE)
                return -EBUSY;
 
-       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;
@@ -12900,7 +12896,7 @@ module_exit(vmx_exit)
 
 static int __init vmx_init(void)
 {
-       int r;
+       int r, cpu;
 
        r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
                     __alignof__(struct vcpu_vmx), THIS_MODULE);
@@ -12922,6 +12918,12 @@ static int __init vmx_init(void)
                }
        }
 
+       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);