Re: [PATCH v2 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V

[Nuno Das Neves]

On 8/21/2023 11:18 AM, Saurabh Singh Sengar wrote:
> 
> 
>> -----Original Message-----
>> From: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx>
>> Sent: Friday, August 18, 2023 3:32 AM
>> To: linux-hyperv@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
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>> arch@xxxxxxxxxxxxxxx
>> Cc: patches@xxxxxxxxxxxxxxx; Michael Kelley (LINUX)
>> <mikelley@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>;
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>> Subject: [PATCH v2 15/15] Drivers: hv: Add modules to expose /dev/mshv to
>> VMMs running on Hyper-V
>>
>> Add mshv, mshv_root, and mshv_vtl modules:
>>
> 
> <snip>
> 
>> +	ret = mshv_set_vp_registers(vp->index, vp->partition->id,
>> +				    1, &dispatch_suspend);
>> +	if (ret)
>> +		pr_err("%s: failed to suspend partition %llu vp %u\n",
>> +			__func__, vp->partition->id, vp->index);
>> +
>> +	return ret;
>> +}
>> +
>> +static int
>> +get_vp_signaled_count(struct mshv_vp *vp, u64 *count)
>> +{
>> +	int ret;
>> +	struct hv_register_assoc root_signal_count = {
>> +		.name = HV_REGISTER_VP_ROOT_SIGNAL_COUNT,
>> +	};
>> +
>> +	ret = mshv_get_vp_registers(vp->index, vp->partition->id,
>> +				    1, &root_signal_count);
>> +
>> +	if (ret) {
>> +		pr_err("%s: failed to get root signal count for partition %llu vp
>> %u",
>> +			__func__, vp->partition->id, vp->index);
>> +		*count = 0;
> 
> Have we missed a return here ?
> Moreover, the return type of this function is never checked consider
> checking it or change it to void.
> 

Thanks, we do need to return here.

This function is called on a cleanup path (deleting the guest VM), so if it fails
something is wrong. Instead of returning void, I think we should check the return
value with WARN_ON(), and abort the cleanup if it failed.

>> +
>> +/* Retrieve and stash the supported scheduler type */
>> +static int __init mshv_retrieve_scheduler_type(void)
>> +{
>> +	struct hv_input_get_system_property *input;
>> +	struct hv_output_get_system_property *output;
>> +	unsigned long flags;
>> +	u64 status;
>> +
>> +	local_irq_save(flags);
>> +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
>> +	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
>> +
>> +	memset(input, 0, sizeof(*input));
>> +	memset(output, 0, sizeof(*output));
>> +	input->property_id = HV_SYSTEM_PROPERTY_SCHEDULER_TYPE;
>> +
>> +	status = hv_do_hypercall(HVCALL_GET_SYSTEM_PROPERTY, input,
>> output);
>> +	if (!hv_result_success(status)) {
>> +		local_irq_restore(flags);
>> +		pr_err("%s: %s\n", __func__, hv_status_to_string(status));
>> +		return hv_status_to_errno(status);
>> +	}
>> +
>> +	hv_scheduler_type = output->scheduler_type;
>> +	local_irq_restore(flags);
>> +
>> +	pr_info("mshv: hypervisor using %s\n",
>> scheduler_type_to_string(hv_scheduler_type));
> 
> Nit: In this file we are using two styles of prints, few are appended with
> "mshv:" and few with "__func__".  It's better to have a single style
> for one module.

Thanks, I'll switch them all to __func__