linux-kernel - Re: [RESEND PATCH] xen: vcpu_info would be reset to wrong place on canceled suspend on PVOPS VM which has multi-cpu

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Date:	Tue, 5 May 2015 18:21:25 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	"Ouyang Zhaowei (Charles)" <ouyangzhaowei@...wei.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	<linux-kernel@...r.kernel.org>,
	Dingweiping <weiping.ding@...wei.com>,
	Yanqiangjun <yanqiangjun@...wei.com>, <jinjian@...wei.com>
Subject: Re: [RESEND PATCH] xen: vcpu_info would be reset to wrong place on
 canceled suspend on PVOPS VM which has multi-cpu

On 05/05/15 14:19, Ouyang Zhaowei (Charles) wrote:
> 
> 
> On 2015.5.5 17:09, David Vrabel wrote:
>> On 04/05/15 03:56, Ouyang Zhaowei (Charles) wrote:
>>> The hypervisor continues assuming that vcpu_info is stored in per-cpu data which was set up by xen_vcpu_setup(),
>>> while on canceled suspend, the call to xen_hvm_init_shared_info() will now make the guest think that vcpu_info
>>> is in the shared page, so we do not call xen_hvm_init_shared_info() on suspend canceled.
>>
>> I don't understand what the impact of this fix is.  Can you include this
>> in the commit message?
>>
>> David
> 
> Sure, please let me know if there is anything not clear enough.
> 
> vcpu_info would be reset to wrong place on canceled suspend on PVOPS VM which has multi-cpu
> 
> The hypervisor continues assuming that vcpu_info is stored in per-cpu data which was set up by xen_vcpu_setup(),
> while on canceled suspend, the call to xen_hvm_init_shared_info() will make the guest think that vcpu_info
> is in the shared page. This will cause non-boot cpus keep checking a wrong vcpu_info address and can not handle
> irqs any more after suspend canceled, for example after we do "xl save -c/restore", PVOPS VM can not be resumed
> as the cpus can not finish their irqs.

Ok, so it's only cancelled suspends that are affected.  Can you make the
clear in the commit and resubmit.  This looks like something that should
be tagged for stable as well.

David

> 
>>
>>> Signed-off-by: Charles Ouyang <ouyangzhaowei@...wei.com>
>>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>>> ---
>>>  arch/x86/xen/suspend.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
>>> index d949769..b2bed45 100644
>>> --- a/arch/x86/xen/suspend.c
>>> +++ b/arch/x86/xen/suspend.c
>>> @@ -32,7 +32,8 @@ static void xen_hvm_post_suspend(int suspend_cancelled)
>>>  {
>>>  #ifdef CONFIG_XEN_PVHVM
>>>         int cpu;
>>> -       xen_hvm_init_shared_info();
>>> +       if (!suspend_cancelled)
>>> +               xen_hvm_init_shared_info();
>>>         xen_callback_vector();
>>>         xen_unplug_emulated_devices();
>>>         if (xen_feature(XENFEAT_hvm_safe_pvclock)) {
>>>
>>
>>
>> .
>>
> 

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