Re: [PATCH] KVM: nVMX: Skip PF interception check when queuing during nested run

[Jan Kiszka <jan.kiszka@web.de>]

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On 2013-04-28 18:20, Ren, Yongjie wrote:
>> -----Original Message-----
>> From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org]
>> On Behalf Of Gleb Natapov
>> Sent: Sunday, April 28, 2013 10:34 PM
>> To: Ren, Yongjie
>> Cc: Jan Kiszka; Marcelo Tosatti; kvm; Nakajima, Jun
>> Subject: Re: [PATCH] KVM: nVMX: Skip PF interception check when queuing
>> during nested run
>>
>> On Sun, Apr 28, 2013 at 02:30:38PM +0000, Ren, Yongjie wrote:
>>>> -----Original Message-----
>>>> From: kvm-owner@vger.kernel.org
>> [mailto:kvm-owner@vger.kernel.org]
>>>> On Behalf Of Jan Kiszka
>>>> Sent: Sunday, April 28, 2013 3:25 PM
>>>> To: Gleb Natapov; Marcelo Tosatti
>>>> Cc: kvm; Nakajima, Jun; Ren, Yongjie
>>>> Subject: [PATCH] KVM: nVMX: Skip PF interception check when queuing
>>>> during nested run
>>>>
>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>>
>>>> While a nested run is pending, vmx_queue_exception is only called to
>>>> requeue exceptions that were previously picked up via
>>>> vmx_cancel_injection. Therefore, we must not check for PF interception
>>>> by L1, possibly causing a bogus nested vmexit.
>>>>
>>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>>> ---
>>>>
>>>> This and the KVM_REQ_IMMEDIATE_EXIT fix allows me to boot an L2
>> Linux
>>>> without problems. Yongjie, please check if it resolves your issue(s) as
>>>> well.
>>>>
>>> The two patches can fix my issue. When both of them are applied, I can
>> have
>>> more tests against next branch.
>> They are both applied now.
>>
> There's some bug in Jan's patch "Rework request for immediate exit".
> When I said 2 patches can fix my issue, I meant his original two patches.
> "Check KVM_REQ_IMMEDIATE_EXIT after enable_irq_window" works for me. 
> "Rework request for immediate exit" patch is buggy.
> In L1, I can get the following error. (also some NMI in L2.)  
> (BTW, I'll have holidays this week. I may not track this issue this week.)
> [  167.252260] NMI backtrace for cpu 1
> [  167.253007] CPU 1
> [  167.253007] Pid: 0, comm: swapper/1 Tainted: GF            3.8.5 #1 Bochs Bochs
> [  167.253007] RIP: 0010:[<ffffffff81045606>]  [<ffffffff81045606>] native_safe_halt+0x6/0x10
> [  167.253007] RSP: 0018:ffff880290d51ed8  EFLAGS: 00000246
> [  167.253007] RAX: 0000000000000000 RBX: ffff880290d50010 RCX: 0140000000000000
> [  167.253007] RDX: 0000000000000000 RSI: 0140000000000000 RDI: 0000000000000086
> [  167.253007] RBP: ffff880290d51ed8 R08: 0000000000000000 R09: 0000000000000000
> [  167.253007] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
> [  167.253007] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> [  167.253007] FS:  0000000000000000(0000) GS:ffff88029fc40000(0000) knlGS:0000000000000000
> [  167.253007] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  167.253007] CR2: ffffffffff600400 CR3: 000000028f12d000 CR4: 00000000000427e0
> [  167.253007] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  167.253007] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [  167.253007] Process swapper/1 (pid: 0, threadinfo ffff880290d50000, task ffff880290d49740)
> [  167.253007] Stack:
> [  167.253007]  ffff880290d51ef8 ffffffff8101d5cf ffff880290d50010 ffffffff81ce0680
> [  167.253007]  ffff880290d51f28 ffffffff8101ce99 ffff880290d51f18 1de4884102b62f69
> [  167.253007]  0000000000000000 0000000000000000 ffff880290d51f48 ffffffff81643595
> [  167.253007] Call Trace:
> [  167.253007]  [<ffffffff8101d5cf>] default_idle+0x4f/0x1a0
> [  167.253007]  [<ffffffff8101ce99>] cpu_idle+0xd9/0x120
> [  167.253007]  [<ffffffff81643595>] start_secondary+0x24c/0x24e
> [  167.253007] Code: 00 00 00 00 00 55 48 89 e5 fa c9 c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb c9 c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <c9> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 c9 c3 66 0f 1f 84
> [  167.248015] NMI backtrace for cpu 3
> [  167.248015] CPU 3
> [  167.248015] Pid: 0, comm: swapper/3 Tainted: GF            3.8.5 #1 Bochs Bochs
> [  167.248015] RIP: 0010:[<ffffffff810454ca>]  [<ffffffff810454ca>] native_write_msr_safe+0xa/0x10
> .......
> 

Argh, of course: We use enable_irq_window also for the NMI window in
certain scenarios. So enable_nmi_window must be changed accordingly.
Will send a patch.

Thanks,
Jan


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