From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kashyap Chamarthy <kchamart@redhat.com>
Subject: Re: [nVMX] With 3.20.0-0.rc0.git5.1 on L0, booting L2 guest results
 in L1 *rebooting*
Date: Thu, 19 Feb 2015 13:07:19 +0100
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Cc: Jan Kiszka <jan.kiszka@siemens.com>, kvm@vger.kernel.org,
	dgilbert@redhat.com
To: Paolo Bonzini <pbonzini@redhat.com>
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On Wed, Feb 18, 2015 at 05:42:37PM +0100, Paolo Bonzini wrote:
> 
> 
> On 17/02/2015 12:24, Kashyap Chamarthy wrote:
> > Afraid, I didn't bisect it, but I just wanted to note that the above
> > specific WARN was introduced in the above commit.
> > 
> > I'm sure this Kernel (on L0) does not exhibit the problem:
> > kernel-3.17.4-301.fc21.x86_64. But, if I had either of these two Kernels
> > on the physical host, then the said problem manifests (L1 reboots):
> > 3.19.0-1.fc22 or kernel-3.20.0-0.rc0.git5.1.fc23
> 
> Nested APICv is not part of 3.19, so it cannot be the culprit.
> 
> Can you try 3.18?

Just did two tests with 3.18:

(1) Kernel 3.18 on L0 and 3.20 on L1

    Result: Booting L2 guest causes L1 to reboot, and the same[*] stack
            trace on L0 (mentioned on this thread previously).

            But, annoyingly enough, when I did test (2) below, and then
            switched back to test (1), I don't notice the said stack
            trace in L0's `dmesg` however many times I boot an L2 guest.

(2) Kernel 3.18 on both L0 and L1

    Result: Booting L2 guest causes L1 to reboot, but *no* stack trace
            on L0



[*] Stack trace from test (1)

. . .
[ 4120.296552] ------------[ cut here ]------------
[ 4120.301190] WARNING: CPU: 6 PID: 1841 at arch/x86/kvm/vmx.c:8962 nested_vmx_vmexit+0x7ee/0x880 [kvm_intel]()
[ 4120.311048] Modules linked in: xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack tun bridge stp llc ip6table_filter ip6_tables cfg80211 rfkill coretemp kvm_intel kvm iTCO_wdt gpio_ich iTCO_vendor_support joydev crc32c_intel lpc_ich ipmi_devintf ipmi_si tpm_tis shpchp i7core_edac dcdbas mfd_core tpm ipmi_msghandler serio_raw edac_core acpi_power_meter wmi acpi_cpufreq mgag200 i2c_algo_bit drm_kms_helper ttm drm megaraid_sas ata_generic bnx2 pata_acpi
[ 4120.361643] CPU: 6 PID: 1841 Comm: qemu-system-x86 Not tainted 3.18.7-200.fc21.x86_64 #1
[ 4120.369757] Hardware name: Dell Inc. PowerEdge R910/0P658H, BIOS 2.8.2 10/25/2012
[ 4120.377269]  0000000000000000 00000000e947d406 ffff88bf21f27c48 ffffffff8175e686
[ 4120.384866]  0000000000000000 0000000000000000 ffff88bf21f27c88 ffffffff810991d1
[ 4120.392469]  ffff88bf21f27c98 ffff887f1f73e000 0000000000000000 0000000000000014
[ 4120.400033] Call Trace:
[ 4120.402533]  [<ffffffff8175e686>] dump_stack+0x46/0x58
[ 4120.407714]  [<ffffffff810991d1>] warn_slowpath_common+0x81/0xa0
[ 4120.413740]  [<ffffffff810992ea>] warn_slowpath_null+0x1a/0x20
[ 4120.419611]  [<ffffffffa1cee0ee>] nested_vmx_vmexit+0x7ee/0x880 [kvm_intel]
[ 4120.426609]  [<ffffffffa1cee5af>] ? vmx_handle_exit+0x1bf/0xaa0 [kvm_intel]
[ 4120.433585]  [<ffffffffa1cee39c>] vmx_queue_exception+0xfc/0x150 [kvm_intel]
[ 4120.440697]  [<ffffffffa0192dfd>] kvm_arch_vcpu_ioctl_run+0xd9d/0x1290 [kvm]
[ 4120.447783]  [<ffffffffa018e528>] ? kvm_arch_vcpu_load+0x58/0x220 [kvm]
[ 4120.454436]  [<ffffffffa017acbc>] kvm_vcpu_ioctl+0x32c/0x5c0 [kvm]
[ 4120.460650]  [<ffffffff817634cd>] ? down_read+0x1d/0x30
[ 4120.465915]  [<ffffffff8122a1c0>] do_vfs_ioctl+0x2d0/0x4b0
[ 4120.471431]  [<ffffffff8122a421>] SyS_ioctl+0x81/0xa0
[ 4120.476477]  [<ffffffff81765429>] system_call_fastpath+0x12/0x17
[ 4120.482533] ---[ end trace 5410644656637166 ]---
[ 4128.015867] kvm [1768]: vcpu0 unhandled rdmsr: 0x1c9
[ 4128.020849] kvm [1768]: vcpu0 unhandled rdmsr: 0x1a6
[ 4128.025848] kvm [1768]: vcpu0 unhandled rdmsr: 0x3f6
. . .

-- 
/kashyap