linux-kernel - Re: [PATCH v10 13/26] gunyah: vm_mgr: Add ioctls to support basic non-proxy VM boot

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Date:   Mon, 20 Feb 2023 15:24:42 +0530
From:   Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>
To:     Elliot Berman <quic_eberman@...cinc.com>
CC:     Alex Elder <elder@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v10 13/26] gunyah: vm_mgr: Add ioctls to support basic
 non-proxy VM boot

* Srivatsa Vaddagiri <quic_svaddagi@...cinc.com> [2023-02-20 14:45:55]:

> * Elliot Berman <quic_eberman@...cinc.com> [2023-02-14 13:24:26]:
> 
> >  static void gh_vm_free(struct work_struct *work)
> >  {
> >  	struct gh_vm *ghvm = container_of(work, struct gh_vm, free_work);
> >  	struct gh_vm_mem *mapping, *tmp;
> >  	int ret;
> >  
> > -	mutex_lock(&ghvm->mm_lock);
> > -	list_for_each_entry_safe(mapping, tmp, &ghvm->memory_mappings, list) {
> > -		gh_vm_mem_reclaim(ghvm, mapping);
> > -		kfree(mapping);
> > +	switch (ghvm->vm_status) {
> > +unknown_state:
> > +	case GH_RM_VM_STATUS_RUNNING:
> > +		gh_vm_stop(ghvm);
> > +		fallthrough;
> > +	case GH_RM_VM_STATUS_INIT_FAILED:
> > +	case GH_RM_VM_STATUS_LOAD:
> > +	case GH_RM_VM_STATUS_LOAD_FAILED:
> > +		mutex_lock(&ghvm->mm_lock);
> > +		list_for_each_entry_safe(mapping, tmp, &ghvm->memory_mappings, list) {
> > +			gh_vm_mem_reclaim(ghvm, mapping);
> > +			kfree(mapping);
> > +		}
> > +		mutex_unlock(&ghvm->mm_lock);
> > +		fallthrough;
> > +	case GH_RM_VM_STATUS_NO_STATE:
> > +		ret = gh_rm_dealloc_vmid(ghvm->rm, ghvm->vmid);
> > +		if (ret)
> > +			pr_warn("Failed to deallocate vmid: %d\n", ret);
> > +
> > +		gh_rm_notifier_unregister(ghvm->rm, &ghvm->nb);
> > +		put_gh_rm(ghvm->rm);
> > +		kfree(ghvm);
> > +		break;
> > +	default:
> > +		pr_err("VM is unknown state: %d, assuming it's running.\n", ghvm->vm_status);
> > +		goto unknown_state;
> 
> 'goto unknown_state' here leads to a infinite loop AFAICS. For example consider
> the case  where VM_START failed (due to mem_lend operation) causing VM state to
> be GH_RM_VM_STATUS_RESET. A subsequent close(vmfd) can leads to that forever
> loop.

Hmm ..that's not a good example perhaps (VM state is set to
GH_RM_VM_STATUS_INIT_FAILED in failed case). Nevertheless I think we should
avoid the goto in case of unknown state.


- vatsa