Messages in this thread | | | Date | Tue, 9 Sep 2008 08:20:56 +0800 | From | Yan Li <> | Subject | Re: [PATCH 1/2] VMware detection support for x86 and x86-64 |
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On Mon, Sep 08, 2008 at 04:04:23PM +0200, Ingo Molnar wrote: > hm, i know it's not your fault as you just took this vmware code, but > this is really not an acceptable method of detection. The above is > totally unsafe to do on native hardware - we dont know whether there's > anything on that port.
Yeah, I agree with you, it's a bad method. I just took it for granted that vmware has done the necessary study and they knew what they were doing. I have tested it on two boxes so I thought they were OK. Now I agree it's a bit dangerous to put this in a general purpose kernel.
> vmware could have used one of the following methods to communicate to > the guest kernel: > > - a CPUID and an MSR range - like a good virtual CPU should. That way > even bootloaders could detect the presence of vmware.
They haven't done this. Per VMware's design, the cpuinfo in virtual guest is identical to the underlying physical CPU. I guess they want to send most of the code to run on underlying CPU directly and won't have to do code mutation or emulation and get better performance.
> - or a PCI ID and a PCI driver like KVM does
Yup. But checking DMI would be easier for us.
> - or a system call hypercall gateway like Xen and KVM does
I think they didn't use this way cause VMware wanted it to be OS-neutral.
> - or it could even have used a DMI signature of some sort
Some people are using this idea. From dmidcode, the VMware-related parts are:
Handle 0x0001, DMI type 1, 25 bytes System Information Manufacturer: VMware, Inc. Product Name: VMware Virtual Platform Version: None Serial Number: VMware-56 4d d2 bf 8d ea 6e ec-81 67 6d 50 42 72 07 46 UUID: 564DD2BF-8DEA-6EEC-8167-6D5042720746 Wake-up Type: Power Switch ............
Handle 0x001A, DMI type 10, 8 bytes On Board Device 1 Information Type: Video Status: Disabled Description: VMware SVGA II
I think it's pretty safe to assume all VMware products include "[VM|vm]ware" in the manufacturer.
> but no, vmware had to use 30 year old unsafe ISA port magic... > > To add insult to injury that port is named 'backdoor' - very smart and > confidence raising naming. Plus it does not even use some well-known PC > port that is harmless to read - it has to be from the middle of the > generic IO port resource range where a real PCI card could sit: 0x5658. > Brilliant. > > is there really no vmware PCI ID to query? Could you post the lspci -v > output of your vmware guest? We could add an early-quirk for one of the > core vmware PCI devices (in case there are any - i bet there are).
VMware may change the PCI ID at their will so I prefer checking the DMI since it's easier.
So if we ditched the official method we run the risk of some false negatives. But checking the DMI manufacturer would be good enough.
-- Li, Yan
"Everything that is really great and inspiring is created by the individual who can labor in freedom." - Albert Einstein, in Out of My Later Years (1950)
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