Messages in this thread | | | Subject | Re: [PATCH 3/4] x86,module: Detect VMX vs SLD conflicts | From | Paolo Bonzini <> | Date | Tue, 7 Apr 2020 16:44:57 +0200 |
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On 07/04/20 16:35, Greg KH wrote: > On Tue, Apr 07, 2020 at 01:02:39PM +0200, Peter Zijlstra wrote: >> It turns out that with Split-Lock-Detect enabled (default) any VMX >> hypervisor needs at least a little modification in order to not blindly >> inject the #AC into the guest without the guest being ready for it. >> >> Since there is no telling which module implements a hypervisor, scan >> all out-of-tree modules' text and look for VMX instructions and refuse >> to load it when SLD is enabled (default) and the module isn't marked >> 'sld_safe'. >> >> Hypervisors, which have been modified and are known to work correctly, >> can add: >> >> MODULE_INFO(sld_safe, "Y"); >> >> to explicitly tell the module loader they're good. > > What's to keep any out-of-tree module from adding this same module info > "flag" and just lie about it? Isn't that what you are trying to catch > here, or is it a case of, "if you lie, your code will break" as well?
It's the latter. Basically it's doing _the users_ of out-of-tree modules a favor by avoiding crashes of their virtual machines; developers need to fix them anyway.
Paolo
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