Re: [PATCH v4 2/2] KVM: nVMX: Fix preemption timer bit set in vmcs02 even if L1 doesn't enable it

From: Paolo Bonzini <pbonzini@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	kvm <kvm@vger.kernel.org>, "Wanpeng Li" <wanpeng.li@hotmail.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Yunhong Jiang" <yunhong.jiang@intel.com>,
	"Jan Kiszka" <jan.kiszka@siemens.com>,
	"Haozhong Zhang" <haozhong.zhang@intel.com>
Subject: Re: [PATCH v4 2/2] KVM: nVMX: Fix preemption timer bit set in vmcs02 even if L1 doesn't enable it
Date: Fri, 8 Jul 2016 17:47:05 +0200	[thread overview]
Message-ID: <d52f76ad-8718-77f6-b74a-648b3e3f8dba@redhat.com> (raw)
In-Reply-To: <CANRm+Cz=QykSTLJz8qyirhhmNTHteRd7aKmkS_m76N9Cr8M0Qw@mail.gmail.com>

On 08/07/2016 16:08, Wanpeng Li wrote:
> 2016-07-08 21:58 GMT+08:00 Wanpeng Li <kernellwp@gmail.com>:
>> We can't get preemption timer vmexit which vmcs02 is loaded since
>> preemtion timer bit in vmcs02 is not set, then how can we get the
>> incorrect preemption timer vmexit in nested guest which patch 1 fixed?
>> Because the scenario I mentioned in patch 2 set vmcs02.
>>
>> w/o patch1 + w/o enable "L1 TSC deadline timer to trigger while L2 is
>> running"  => we will get the bug calltrace mentioned in patch1 since
>> incorrect vmcs02 bit is set due to the bug mentioned in patch 2. So
>> apply patch2 can fix it.
>>
>> However, after enable "L1 TSC deadline timer to trigger while L2 is
>> running", we should have patch 1 to correctly capture nested vmexit
>> for preemption timer.
>>
>> My setup is L0 and L1 both are latest kvm queue branch w/ Yunhong's
>> preemption timer enable patches and my previous "fix missed
>> cancellation of TSC deadline timer" patches. I always enable
>> preemption timer in L0, but try to enable or disable preemption timer
>> in L1.
> 
> Btw, my L1 is a full dynticks guest in order that hrtimer in L1 will
> be heavily used.

Thanks---I'd be grateful if you tested my patch series.

Paolo