Re: [PATCH resend v5 6/6] KVM: nVMX: Enable nested posted interrupt processing

[Wanpeng Li <wanpeng.li@linux.intel.com>]

Cc Rongrong,
On Fri, Feb 27, 2015 at 04:56:06PM +0800, Wincy Van wrote:
>On Sun, Feb 15, 2015 at 2:27 PM, Yong Wang <yong.y.wang@linux.intel.com> 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
>
>
>Thanks,
>Wincy