Commit dbef2808 authored Apr 01, 2020 by Vitaly Kuznetsov Committed by Paolo Bonzini Apr 07, 2020

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



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: 31603d4f ("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>

parent 4064a4c6

arch/x86/kvm/vmx/vmx.c

+7 −5

Original line number	Diff line number	Diff line
		@@ -2261,10 +2261,6 @@ 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));

		r = kvm_cpu_vmxon(phys_addr);
		if (r)
		return r;
		@@ -8044,7 +8040,7 @@ module_exit(vmx_exit);

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

		#if IS_ENABLED(CONFIG_HYPERV)
		/*
		@@ -8098,6 +8094,12 @@ 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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