Messages in this thread | | | From | (Eric W. Biederman) | Date | Tue, 04 Dec 2012 12:14:15 -0800 | Subject | Re: [PATCH v9 1/2] x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary |
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Zhang Yanfei <zhangyanfei@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.
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.
Otherwise I have no objections to this code.
Eric
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