From 910053002ef1fdc1d42b7015d5b2400172f43e42 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Wed, 3 Aug 2016 12:04:12 +0800 Subject: KVM: lapic: fix access preemption timer stuff even if kernel_irqchip=off MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit BUG: unable to handle kernel NULL pointer dereference at 000000000000008c IP: [] 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 [] kvm_lapic_hv_timer_in_use+0x10/0x20 [kvm] RSP 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 Cc: Radim Krčmář Cc: Yunhong Jiang Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch') diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 730cf174090a..b62c85229711 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -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); -- cgit v1.2.3-59-g8ed1b