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 21:19:34 +0800
From:	"Ouyang Zhaowei (Charles)" <ouyangzhaowei@...wei.com>
To:	David Vrabel <david.vrabel@...rix.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 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.

> 
>> 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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