[PATCH kernel] KVM: PPC: Book3S HV: Make unique debugfs nodename

[Alexey Kardashevskiy]

On 02/09/2021 00:23, Fabiano Rosas wrote:
> Alexey Kardashevskiy <aik at ozlabs.ru> writes:
> 
>> On 24/08/2021 18:37, Alexey Kardashevskiy wrote:
>>>
>>>
>>> On 18/08/2021 08:20, Fabiano Rosas wrote:
>>>> Alexey Kardashevskiy <aik at ozlabs.ru> writes:
>>>>
>>>>> On 07/07/2021 14:13, Alexey Kardashevskiy wrote:
>>>>
>>>>> alternatively move this debugfs stuff under the platform-independent
>>>>> directory, how about that?
>>>>
>>>> That's a good idea. I only now realized we have two separate directories
>>>> for the same guest:
>>>>
>>>> $ ls /sys/kernel/debug/kvm/ | grep $pid
>>>> 19062-11
>>>> vm19062
>>>>
>>>> Looks like we would have to implement kvm_arch_create_vcpu_debugfs for
>>>> the vcpu information and add a similar hook for the vm.
>>>
>>> Something like that. From the git history, it looks like the ppc folder
>>> was added first and then the generic kvm folder was added but apparently
>>> they did not notice the ppc one due to natural reasons :)
>>>
>>> If you are not too busy, can you please merge the ppc one into the
>>> generic one and post the patch, so we won't need to fix these
>>> duplication warnings again? Thanks,
>>
>>
>>
>> Turns out it is not that straight forward as I thought as the common KVM
>> debugfs entry is created after PPC HV KVM created its own and there is
>> no obvious way to change the order (no "post init" hook in
>> kvmppc_ops).
> 
> That is why I mentioned creating a hook similar to
> kvm_create_vcpu_debugfs in the common KVM code. kvm_create_vm_debugfs or
> something.

ah sorry I missed that :-/


> Alternatively, maybe kvm_create_vm_debugfs could be moved earlier into
> kvm_create_vm, before kvm_arch_post_init_vm and we could move our code
> into kvm_arch_post_init_vm.

kvm_arch_create_vcpu_debugfs() or kvm_arch_post_init_vm() will still 
require hooks in kvmppc_ops and such bikeshedding may take a while :)


>>
>> Also, unlike the common KVM debugfs setup, we do not allocate structures
>> to support debugfs nodes so we do not leak anything to bother with a
>> mutex like 85cd39af14f4 did.
>>
>> So I'd stick to the original patch to reduce the noise in the dmesg, and
>> it also exposes lpid which I find rather useful for finding the right
>> partition scope tree in partition_tb.
>>
>> Michael?
>>
>>
>>>
>>>
>>>
>>>>>> ---
>>>>>>     arch/powerpc/kvm/book3s_hv.c | 2 +-
>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/arch/powerpc/kvm/book3s_hv.c
>>>>>> b/arch/powerpc/kvm/book3s_hv.c
>>>>>> index 1d1fcc290fca..0223ddc0eed0 100644
>>>>>> --- a/arch/powerpc/kvm/book3s_hv.c
>>>>>> +++ b/arch/powerpc/kvm/book3s_hv.c
>>>>>> @@ -5227,7 +5227,7 @@ static int kvmppc_core_init_vm_hv(struct kvm
>>>>>> *kvm)
>>>>>>         /*
>>>>>>          * Create a debugfs directory for the VM
>>>>>>          */
>>>>>> -    snprintf(buf, sizeof(buf), "vm%d", current->pid);
>>>>>> +    snprintf(buf, sizeof(buf), "vm%d-lp%ld", current->pid, lpid);
>>>>>>         kvm->arch.debugfs_dir = debugfs_create_dir(buf,
>>>>>> kvm_debugfs_dir);
>>>>>>         kvmppc_mmu_debugfs_init(kvm);
>>>>>>         if (radix_enabled())
>>>>>>
>>>

-- 
Alexey