linux-kernel - Re: [PATCH v9 22/27] virt: gunyah: Add resource tickets

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Date:   Mon, 6 Feb 2023 15:20:10 +0530
From:   Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>
To:     Elliot Berman <quic_eberman@...cinc.com>
CC:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Alex Elder <elder@...aro.org>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...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>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Sudeep Holla <sudeep.holla@....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 v9 22/27] virt: gunyah: Add resource tickets

* Elliot Berman <quic_eberman@...cinc.com> [2023-01-20 14:46:21]:

> +int ghvm_add_resource_ticket(struct gunyah_vm *ghvm, struct gunyah_vm_resource_ticket *ticket)
> +{
> +	struct gunyah_vm_resource_ticket *iter;
> +	struct gunyah_resource *ghrsc;
> +	int ret = 0;
> +
> +	mutex_lock(&ghvm->resources_lock);
> +	list_for_each_entry(iter, &ghvm->resource_tickets, list) {
> +		if (iter->resource_type == ticket->resource_type && iter->label == ticket->label) {
> +			ret = -EEXIST;
> +			goto out;
> +		}
> +	}
> +
> +	if (!try_module_get(ticket->owner)) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	list_add(&ticket->list, &ghvm->resource_tickets);
> +	INIT_LIST_HEAD(&ticket->resources);
> +
> +	list_for_each_entry(ghrsc, &ghvm->resources, list) {
> +		if (ghrsc->type == ticket->resource_type && ghrsc->rm_label == ticket->label) {
> +			if (!ticket->populate(ticket, ghrsc))
> +				list_move(&ghrsc->list, &ticket->resources);

Do we need the search to continue in case of a hit? 'gh_vm_add_resource' seems to
break loop on first occurrence. 

Also do we have examples of more than one 'gunyah_resource' being associated
with same 'gunyah_vm_resource_ticket'?  Both vcpu and irqfd tickets seem to deal
with just one resource?

>  static int gh_vm_start(struct gunyah_vm *ghvm)
>  {
>  	struct gunyah_vm_memory_mapping *mapping;
>  	u64 dtb_offset;
>  	u32 mem_handle;
> -	int ret;
> +	struct gunyah_resource *ghrsc;
> +	struct gh_rm_hyp_resources *resources;
> +	int ret, i;
>  
>  	down_write(&ghvm->status_lock);
>  	if (ghvm->vm_status != GH_RM_VM_STATUS_NO_STATE) {
> @@ -241,6 +314,22 @@ static int gh_vm_start(struct gunyah_vm *ghvm)
>  		goto err;
>  	}
>  
> +	ret = gh_rm_get_hyp_resources(ghvm->rm, ghvm->vmid, &resources);
> +	if (ret) {
> +		pr_warn("Failed to get hypervisor resources for VM: %d\n", ret);
> +		goto err;
> +	}
> +
> +	for (i = 0; i < le32_to_cpu(resources->n_entries); i++) {

minor nit: not sure if we can rely on compiler to optimize this, but it would
be better if we run le32_to_cpu once and use the result in loop. 

> +		ghrsc = gh_rm_alloc_resource(ghvm->rm, &resources->entries[i]);
> +		if (!ghrsc) {
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		gh_vm_add_resource(ghvm, ghrsc);

Shouldn't we have gh_vm_add_resource()->  ticket->populate() return a result and
in case of failure we should bail out from this loop?

> +	}
> +
>  	ret = gh_rm_vm_start(ghvm->rm, ghvm->vmid);
>  	if (ret) {
>  		pr_warn("Failed to start VM: %d\n", ret);