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

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Date:	Sun, 15 Feb 2015 14:27:55 +0800
From:	Yong Wang <yong.y.wang@...ux.intel.com>
To:	Wincy Van <fanwenyi0529@...il.com>
Cc:	pbonzini@...hat.com, gleb@...nel.org, yang.z.zhang@...el.com,
	wanpeng.li@...ux.intel.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, jan.kiszka@....de
Subject: Re: [PATCH resend v5 6/6] KVM: nVMX: Enable nested posted interrupt
 processing

On Tue, Feb 03, 2015 at 11:58:17PM +0800, Wincy Van wrote:
> If vcpu has a interrupt in vmx non-root mode, we will
> kick that vcpu to inject interrupt timely. With posted
> interrupt processing, the kick intr is not needed, and
> interrupts are fully taken care of by hardware.
> 
> In nested vmx, this feature avoids much more vmexits
> than non-nested vmx.
> 
> This patch use L0's POSTED_INTR_NV to avoid unexpected
> interrupt if L1's vector is different with L0's. If vcpu
> is in hardware's non-root mode, we use a physical ipi to
> deliver posted interrupts, otherwise we will accomplish
> that posted interrupt in nested vm-entry manually.
> 
> Signed-off-by: Wincy Van <fanwenyi0529@...il.com>
> ---
>  arch/x86/kvm/lapic.c |   13 +++-
>  arch/x86/kvm/lapic.h |    1 +
>  arch/x86/kvm/vmx.c   |  151 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 158 insertions(+), 7 deletions(-)
> 

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.

Thanks
-Yong

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