On 06/07/2016 12:29, Wanpeng Li wrote: > 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 is happening in L2, while the patch is for L1, right? So the commit title should be "KVM: nVMX: fix incorrect preemption timer vmexit in nested guest". The patch looks correct, but I'm not sure how you get a preemption timer vmexit while vmcs02 is active: exec_control = vmcs12->pin_based_vm_exec_control; exec_control |= vmcs_config.pin_based_exec_ctrl; exec_control &= ~PIN_BASED_VMX_PREEMPTION_TIMER; In other words, don't you need something like diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index f6e5cc679898..edf925a2da9d 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1121,9 +1121,6 @@ static inline bool cpu_has_broken_vmx_preemption_timer(void) static inline bool cpu_has_vmx_preemption_timer(void) { - if (cpu_has_broken_vmx_preemption_timer()) - return false; - return vmcs_config.pin_based_exec_ctrl & PIN_BASED_VMX_PREEMPTION_TIMER; } @@ -3406,6 +3403,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf) if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_PINBASED_CTLS, &_pin_based_exec_control) < 0) return -EIO; + + if (cpu_has_broken_vmx_preemption_timer()) + _pin_based_exec_control &= ~PIN_BASED_VMX_PREEMPTION_TIMER; if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)) @@ -9797,8 +9796,10 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12) vmcs_write64(VMCS_LINK_POINTER, -1ull); exec_control = vmcs12->pin_based_vm_exec_control; + exec_control &= ~PIN_BASED_VMX_PREEMPTION_TIMER; exec_control |= vmcs_config.pin_based_exec_ctrl; - exec_control &= ~PIN_BASED_VMX_PREEMPTION_TIMER; + if (vmx->hv_deadline_tsc == -1) + exec_control &= ~PIN_BASED_VMX_PREEMPTION_TIMER; if (nested_cpu_has_posted_intr(vmcs12)) { /* for the L1 TSC deadline timer to trigger while L2 is running? It's untested, but this would replace the patch that Haozhong submitted earlier. Paolo > 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> > --- > 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; > } > -- 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