Commit 91005300 authored Aug 03, 2016 by Wanpeng Li Committed by Paolo Bonzini Aug 04, 2016

KVM: lapic: fix access preemption timer stuff even if kernel_irqchip=off



BUG: unable to handle kernel NULL pointer dereference at 000000000000008c
IP: [<ffffffffc04e0180>] kvm_lapic_hv_timer_in_use+0x10/0x20 [kvm]
PGD 0
Oops: 0000 [#1] SMP
Call Trace:
 kvm_arch_vcpu_load+0x86/0x260 [kvm]
 vcpu_load+0x46/0x60 [kvm]
 kvm_vcpu_ioctl+0x79/0x7c0 [kvm]
 ? __lock_is_held+0x54/0x70
 do_vfs_ioctl+0x96/0x6a0
 ? __fget_light+0x2a/0x90
 SyS_ioctl+0x79/0x90
 do_syscall_64+0x7c/0x1e0
 entry_SYSCALL64_slow_path+0x25/0x25
RIP  [<ffffffffc04e0180>] kvm_lapic_hv_timer_in_use+0x10/0x20 [kvm]
 RSP <ffff8800db1f3d70>
CR2: 000000000000008c
---[ end trace a55fb79d2b3b4ee8 ]---

This can be reproduced steadily by kernel_irqchip=off.

We should not access preemption timer stuff if lapic is emulated in userspace.
This patch fix it by avoiding access preemption timer stuff when kernel_irqchip=off.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 055b6ae9

arch/x86/kvm/lapic.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1349,6 +1349,9 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)

		bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
		{
		if (!lapic_in_kernel(vcpu))
		return false;

		return vcpu->arch.apic->lapic_timer.hv_timer_in_use;
		}
		EXPORT_SYMBOL_GPL(kvm_lapic_hv_timer_in_use);

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