On Fri, Feb 27, 2015 at 04:56:06PM +0800, Wincy Van wrote: > On Sun, Feb 15, 2015 at 2:27 PM, Yong Wang <[email protected]> > wrote: > > > > Wincy, our QA found regressions with this patch that 64bit L2 linux guest > > fails to boot up when running nested kvm on kvm. > > > > Environment: > > ------------ > > Host OS (ia32/ia32e/IA64):ia32e > > Guest OS (ia32/ia32e/IA64):ia32e > > Guest OS Type (Linux/Windows):Linux > > kvm.git Commit:6557bada461afeaa920a189fae2cff7c8fdce39f > > qemu.kvm Commit:5c697ae74170d43928cb185f5ac1a9058adcae0b > > Host Kernel Version:3.19.0-rc3 > > Hardware:Ivytown_EP, Haswell_EP > > > > > > Bug detailed description: > > -------------------------- > > create 64bit linux guest as L2 guest, the guest boot up fail > > > > note: > > 1. create a 32bit linux guest as L2 guest, the guest boots up fine. > > 2. create a 64bit windows guest as L2 guest, the guest boots up fine. > > 3. this should be a kernel bug: > > kvm + qemu = result > > 6557bada + 5c697ae7 = bad > > 8fff5e37 + 5c697ae7 = good > > > > Reproduce steps: > > ---------------- > > 1 create L1 guest: > > qemu-system-x86_64 -enable-kvm -m 8G -smp 4 -net > > nic,macaddr=00:12:31:34:51:31 -net tap,script=/etc/kvm/qemu-ifup > > nested-kvm.qcow -cpu host > > > > 2. create L2 guest > > qemu-system-x86_64 -enable-kvm -m 2G -smp 2 -net none rhel6u5.qcow > > > > Current result: > > ---------------- > > create 64bit linux guest as L2 guest, the guest boots up fail > > > > Expected result: > > ---------------- > > create 64bit linux guest as L2 guest, the guest boots up fine > > > > Please take a look. > > > > Yong, according to the logs, I found that L1 may have disabled x2apic, > and the MSR_BITMAP field will be modified by following vmx_set_efer in > prepare_vmcs02. > So I think we can fix this issue by: > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index f7b20b4..f6e3457 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -2168,7 +2168,10 @@ static void vmx_set_msr_bitmap(struct kvm_vcpu *vcpu) > { > unsigned long *msr_bitmap; > > - if (irqchip_in_kernel(vcpu->kvm) && > apic_x2apic_mode(vcpu->arch.apic)) { > + if (is_guest_mode(vcpu)) > + msr_bitmap = vmx_msr_bitmap_nested; > + else if (irqchip_in_kernel(vcpu->kvm) && > + apic_x2apic_mode(vcpu->arch.apic)) { > if (is_long_mode(vcpu)) > msr_bitmap = vmx_msr_bitmap_longmode_x2apic; > else > >
Our QA verified that your patch fixed the issue. Please prepare a formal patch that Paolo can consider applying. Thanks a lot Wincy! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
