? 2012?12?05? 04:14, Eric W. Biederman ??:
> Zhang Yanfei <zhangyanfei at cn.fujitsu.com> writes:
>
>> This patch provides a way to VMCLEAR VMCSs related to guests
>> on all cpus before executing the VMXOFF when doing kdump. This
>> is used to ensure the VMCSs in the vmcore updated and
>> non-corrupted.
>
> Apologies for the delay I have been travelling, and I wanted
> to at least read through the code.
>
> Overall I think this is good but I have one nit, and I see one real
> problem with this code.
>
>> +/*
>> + * This is used to VMCLEAR all VMCSs loaded on the
>> + * processor. And when loading kvm_intel module, the
>> + * callback function pointer will be assigned.
>> + */
>> +void (*crash_vmclear_loaded_vmcss)(void) = NULL;
>> +EXPORT_SYMBOL_GPL(crash_vmclear_loaded_vmcss);
>> +
>> +static inline void cpu_emergency_vmclear_loaded_vmcss(void)
>> +{
>> + if (crash_vmclear_loaded_vmcss)
>> + crash_vmclear_loaded_vmcss();
>> +}
>
> The nit is the use of emergency instead of crash in the name.
ok, emergency -> crash
>
> The problem is that this is potentially a NULL pointer dereference if
> kvm-intel is removed. The easist fix would be in your second patch to
> just make it impossible to unload the kvm-intel module. Otherwise
> there the deference of crash_vmclear_loaded_vmcss needs to be rcu
> protected, with a syncrhonize_rcu after the pointer is set to NULL in
> the unload path.
Ah, thanks for this comment.
I think I will use the rcu machanism to solve the problem.
>
> Otherwise I have no objections to this code.
Thanks for your review. I will update the patch and resend it.
Thanks
Zhang Yanfei
