Re: [PATCH] KVM: MIPS: Change the definition of kvm type

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On 11/09/2020 19.22, Paolo Bonzini wrote:
> On 10/09/20 12:33, Huacai Chen wrote:
>> MIPS defines two kvm types:
>>
>>  #define KVM_VM_MIPS_TE          0
>>  #define KVM_VM_MIPS_VZ          1
>>
>> In Documentation/virt/kvm/api.rst it is said that "You probably want to
>> use 0 as machine type", which implies that type 0 be the "automatic" or
>> "default" type. And, in user-space libvirt use the null-machine (with
>> type 0) to detect the kvm capability, which returns "KVM not supported"
>> on a VZ platform.
>>
>> I try to fix it in QEMU but it is ugly:
>> https://lists.nongnu.org/archive/html/qemu-devel/2020-08/msg05629.html
>>
>> And Thomas Huth suggests me to change the definition of kvm type:
>> https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg03281.html
>>
>> So I define like this:
>>
>>  #define KVM_VM_MIPS_AUTO        0
>>  #define KVM_VM_MIPS_VZ          1
>>  #define KVM_VM_MIPS_TE          2
>>
>> Since VZ and TE cannot co-exists, using type 0 on a TE platform will
>> still return success (so old user-space tools have no problems on new
>> kernels); the advantage is that using type 0 on a VZ platform will not
>> return failure. So, the only problem is "new user-space tools use type
>> 2 on old kernels", but if we treat this as a kernel bug, we can backport
>> this patch to old stable kernels.
> 
> I'm a bit wary to do that.  However it's not an issue for QEMU since it
> generally updates the kernel headers.

Are there any other userspace programs beside QEMU that use KVM on MIPS?
If there aren't any other serious userspace programs, I think we should
go ahead with this patch here. Otherwise, what are the other programs
that could be affected?

 Thomas





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