Re: [PATCH 4/5] PCI/MSI: MSI cleanup, msi_setup_entry()

[Bjorn Helgaas <bhelgaas@google.com>]

On Thu, Jun 19, 2014 at 04:30:48PM +0800, Yijing Wang wrote:
> Move MSI entry stuff to a new function
> msi_setup_entry(), simplify msi_capability_init()
> code like MSI-X do.

I like this in general, but ...

> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> ---
>  drivers/pci/msi.c |   71 +++++++++++++++++++++++++++++++---------------------
>  1 files changed, 42 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index d8e431d..8e17446 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -582,6 +582,35 @@ error_attrs:
>  	return ret;
>  }
>  
> +static int msi_setup_entry(struct pci_dev *dev)
> +{
> +	u16 control;
> +	struct msi_desc *entry;
> +
> +	entry = alloc_msi_entry(dev);
> +	if (!entry)
> +		return -ENOMEM;
> +
> +	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
> +
> +	entry->msi_attrib.is_msix	= 0;
> +	entry->msi_attrib.is_64		= !!(control & PCI_MSI_FLAGS_64BIT);
> +	entry->msi_attrib.entry_nr	= 0;
> +	entry->msi_attrib.maskbit	= !!(control & PCI_MSI_FLAGS_MASKBIT);
> +	entry->msi_attrib.default_irq	= dev->irq;	/* Save IOAPIC IRQ */
> +	entry->msi_attrib.pos		= dev->msi_cap;
> +	entry->msi_attrib.multi_cap = (control & PCI_MSI_FLAGS_QMASK) >> 1;
> +
> +	if (control & PCI_MSI_FLAGS_64BIT)
> +		entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
> +	else
> +		entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_32;
> +
> +
> +	list_add_tail(&entry->list, &dev->msi_list);
> +	return 0;

Why don't you just return "entry" here (and NULL for the failure above)?

> +}
> +
>  /**
>   * msi_capability_init - configure device's MSI capability structure
>   * @dev: pointer to the pci_dev data structure of MSI device function
> @@ -597,51 +626,30 @@ static int msi_capability_init(struct pci_dev *dev, int nvec)
>  {
>  	struct msi_desc *entry;
>  	int ret;
> -	u16 control;
>  	unsigned mask;
>  
>  	msi_set_enable(dev, 0);	/* Disable MSI during set up */
>  
> -	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
>  	/* MSI Entry Initialization */
> -	entry = alloc_msi_entry(dev);
> -	if (!entry)
> -		return -ENOMEM;
> -
> -	entry->msi_attrib.is_msix	= 0;
> -	entry->msi_attrib.is_64		= !!(control & PCI_MSI_FLAGS_64BIT);
> -	entry->msi_attrib.entry_nr	= 0;
> -	entry->msi_attrib.maskbit	= !!(control & PCI_MSI_FLAGS_MASKBIT);
> -	entry->msi_attrib.default_irq	= dev->irq;	/* Save IOAPIC IRQ */
> -	entry->msi_attrib.pos		= dev->msi_cap;
> -	entry->msi_attrib.multi_cap = (control & PCI_MSI_FLAGS_QMASK) >> 1;
> +	ret = msi_setup_entry(dev);
> +	if (ret)
> +		return ret;
>  
> -	if (control & PCI_MSI_FLAGS_64BIT)
> -		entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
> -	else
> -		entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_32;
> +	entry = list_first_entry(&dev->msi_list, struct msi_desc, list);
>  	/* All MSIs are unmasked by default, Mask them all */
>  	if (entry->msi_attrib.maskbit)
>  		pci_read_config_dword(dev, entry->mask_pos, &entry->masked);
>  	mask = msi_mask(entry->msi_attrib.multi_cap);
>  	msi_mask_irq(entry, mask, mask);
>  
> -	list_add_tail(&entry->list, &dev->msi_list);

And keep the list_add_tail() here.  Then you don't have the awkwardness of
pulling the entry off the list after calling msi_setup_entry().

That also means the MSIs can be masked before putting the entry on
dev->msi_list, as they were before.  It *might* be safe to change the order
as you did, but it definitely takes some analysis to prove it, especially
since pci_enable_msi_range() only WARNs but doesn't bail out if
dev->msi_enabled already.

>  	/* Configure MSI capability structure */
>  	ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSI);
> -	if (ret) {
> -		msi_mask_irq(entry, mask, ~mask);
> -		free_msi_irqs(dev);
> -		return ret;
> -	}
> +	if (ret)
> +		goto err;
>  
>  	ret = populate_msi_sysfs(dev);
> -	if (ret) {
> -		msi_mask_irq(entry, mask, ~mask);
> -		free_msi_irqs(dev);
> -		return ret;
> -	}
> +	if (ret)
> +		goto err;
>  
>  	/* Set MSI enabled bits	 */
>  	pci_intx_for_msi(dev, 0);
> @@ -650,6 +658,11 @@ static int msi_capability_init(struct pci_dev *dev, int nvec)
>  
>  	dev->irq = entry->irq;
>  	return 0;
> +
> +err:
> +	msi_mask_irq(entry, mask, ~mask);
> +	free_msi_irqs(dev);
> +	return ret;
>  }
>  
>  static void __iomem *msix_map_region(struct pci_dev *dev, unsigned nr_entries)
> -- 
> 1.7.1
> 
> 
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