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

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Date:   Wed, 07 Jul 2021 14:48:43 -0300
From:   Fabiano Rosas <farosas@...ux.ibm.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>, linuxppc-dev@...ts.ozlabs.org
Cc:     Alexey Kardashevskiy <aik@...abs.ru>, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org, Paul Mackerras <paulus@...abs.org>
Subject: Re: [PATCH kernel] KVM: PPC: Book3S HV: Make unique debugfs nodename

Alexey Kardashevskiy <aik@...abs.ru> writes:

> Currently it is vm-$currentpid which works as long as there is just one
> VM per the userspace (99.99% cases) but produces a bunch
> of "debugfs: Directory 'vm16679' with parent 'kvm' already present!"
> when syzkaller (syscall fuzzer) is running so only one VM is present in
> the debugfs for a given process.
>
> This changes the debugfs node to include the LPID which alone should be
> system wide unique. This leaves the existing pid for the convenience of
> matching the VM's debugfs with the running userspace process (QEMU).
>
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>

Reviewed-by: Fabiano Rosas <farosas@...ux.ibm.com>

> ---
>  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())