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

Alexey Kardashevskiy [off-list ref] writes:

On 24/08/2021 18:37, Alexey Kardashevskiy wrote:

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On 18/08/2021 08:20, Fabiano Rosas wrote:

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Alexey Kardashevskiy [off-list ref] writes:

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On 07/07/2021 14:13, Alexey Kardashevskiy wrote:

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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.

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.

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?

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---
   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())