Re: [PATCH] pci-hyperv: use kmalloc to allocate hypercall params buffer

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue,  8 Nov 2016 14:04:38 -0800
Long Li <longli@exchange.microsoft.com> wrote:

> +	spin_lock_irqsave(&hbus->retarget_msi_interrupt_lock, flags);
> +
> +	params = &hbus->retarget_msi_interrupt_params;
> +	memset(params, 0, sizeof(*params));
> +	params->partition_id = HV_PARTITION_ID_SELF;
> +	params->source = 1; /* MSI(-X) */
> +	params->address = msi_desc->msg.address_lo;
> +	params->data = msi_desc->msg.data;
> +	params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
>  			   (hbus->hdev->dev_instance.b[4] << 16) |
>  			   (hbus->hdev->dev_instance.b[7] << 8) |
>  			   (hbus->hdev->dev_instance.b[6] & 0xf8) |
>  			   PCI_FUNC(pdev->devfn);
> -	params.vector = cfg->vector;
> +	params->vector = cfg->vector;
>  
>  	for_each_cpu_and(cpu, dest, cpu_online_mask)
> -		params.vp_mask |= (1ULL << vmbus_cpu_number_to_vp_number(cpu));
> +		params->vp_mask |= (1ULL << vmbus_cpu_number_to_vp_number(cpu));
> +
> +	hv_do_hypercall(HVCALL_RETARGET_INTERRUPT, params, NULL);
>  
> -	hv_do_hypercall(HVCALL_RETARGET_INTERRUPT, &params, NULL);
> +	spin_unlock_irqrestore(&hbus->retarget_msi_interrupt_lock, flags);

It looks like the additional locking here is being overly paranoid.
The caller is already holding the irq descriptor lock. Look at fixup_irqs.