On Thu, 7 Jul 2016 14:29:45 +0200 Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > On 07/07/2016 14:18, Wanpeng Li wrote: > > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > > > BUG: unable to handle kernel NULL pointer dereference at > > (null) IP: [< (null)>] (null) > > PGD 0 > > Oops: 0010 [#1] SMP > > Call Trace: > > ? kvm_lapic_expired_hv_timer+0x47/0x90 [kvm] > > handle_preemption_timer+0xe/0x20 [kvm_intel] > > vmx_handle_exit+0x169/0x15a0 [kvm_intel] > > ? kvm_arch_vcpu_ioctl_run+0xd5d/0x19d0 [kvm] > > kvm_arch_vcpu_ioctl_run+0xdee/0x19d0 [kvm] > > ? kvm_arch_vcpu_ioctl_run+0xd5d/0x19d0 [kvm] > > ? vcpu_load+0x1c/0x60 [kvm] > > ? kvm_arch_vcpu_load+0x57/0x260 [kvm] > > kvm_vcpu_ioctl+0x2d3/0x7c0 [kvm] > > do_vfs_ioctl+0x96/0x6a0 > > ? __fget_light+0x2a/0x90 > > SyS_ioctl+0x79/0x90 > > do_syscall_64+0x68/0x180 > > entry_SYSCALL64_slow_path+0x25/0x25 > > Code: Bad RIP value. > > RIP [< (null)>] (null) > > RSP <ffff8800b5263c48> > > CR2: 0000000000000000 > > ---[ end trace 9c70c48b1a2bc66e ]--- > > > > This can be reproduced readily by preemption timer enabled on L0 > > and disabled on L1. > > > > Preemption timer for nested VMX is emulated by hrtimer which is > > started on L2 entry, stopped on L2 exit and evaluated via the > > check_nested_events hook. However, nested_vmx_exit_handled is > > always return true for preemption timer vmexit, then the L1 > > preemption timer vmexit is captured and be treated as a L2 > > preemption timer vmexit, incurr a nested vmexit dereference NULL > > pointer. > > > > This patch fix it by depending on check_nested_events to capture L2 > > preemption timer(emulated hrtimer) expire and nested vmexit. > > > > Tested-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx> > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > > Cc: Yunhong Jiang <yunhong.jiang@xxxxxxxxx> > > Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> > > Cc: Haozhong Zhang <haozhong.zhang@xxxxxxxxx> > > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > --- > > v2 -> v3: > > * update patch subject > > v1 -> v2: > > * fix typo in patch description > > > > arch/x86/kvm/vmx.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > > index 85e2f0a..29c16a8 100644 > > --- a/arch/x86/kvm/vmx.c > > +++ b/arch/x86/kvm/vmx.c > > @@ -8041,6 +8041,8 @@ static bool nested_vmx_exit_handled(struct > > kvm_vcpu *vcpu) return nested_cpu_has2(vmcs12, > > SECONDARY_EXEC_XSAVES); case EXIT_REASON_PCOMMIT: > > return nested_cpu_has2(vmcs12, > > SECONDARY_EXEC_PCOMMIT); > > + case EXIT_REASON_PREEMPTION_TIMER: > > + return false; > > default: > > return true; > > } > > > > Thanks, applied to kvm/queue. > > Paolo Just back from vocation and see this issue. Really sorry that I didn't consider the nested VM situation when working on the original patch. Paolo/Wanpeng/Haozhong, thanks for the patch. --jyh -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
