Subject: Re: [PATCH v2 04/22] x86/xen/MSI: Eliminate arch_msix_mask_irq() and arch_msi_mask_irq()

From: Konrad Rzeszutek Wilk <[email-masked]>
Date: Thu, 25 Sep 2014 10:33:46 -0400

On Thu, Sep 25, 2014 at 11:14:14AM +0800, Yijing Wang wrote:
> Commit 0e4ccb150 added two __weak arch functions arch_msix_mask_irq()
> and arch_msi_mask_irq() to fix a bug found when running xen in x86.
> Introduced these two funcntions make MSI code complex. And mask/unmask

"These two functions made the MSI code more complex."
> is the irq actions related to interrupt controller, should not use
> weak arch functions to override mask/unmask interfaces. This patch

I am bit baffled of what you are saying.
> reverted commit 0e4ccb150 and export struct irq_chip msi_chip, modify
> msi_chip->irq_mask/irq_unmask() in xen init functions to fix this
> bug for simplicity. Also this is preparation for using struct
> msi_chip instead of weak arch MSI functions in all platforms.
> Keep default_msi_mask_irq() and default_msix_mask_irq() in
> linux/msi.h to make s390 MSI code compile happy, they wiil be removed

s/wiil/will.

> in the later patch.
> 
> Tested-by: Konrad Rzeszutek Wilk <[email-masked]>

I don't even remember testing it - I guess I did the earlier version.

So a couple of questions since I've totally forgotten about this:

> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 50f67a3..5f8f3af 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -162,7 +162,7 @@ static inline __attribute_const__ u32 msi_mask(unsigned x)
>   * reliably as devices without an INTx disable bit will then generate a
>   * level IRQ which will never be cleared.
>   */
> -u32 default_msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
> +u32 __msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
>  {
>  	u32 mask_bits = desc->masked;
>  
> @@ -176,14 +176,9 @@ u32 default_msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
>  	return mask_bits;
>  }
>  
> -__weak u32 arch_msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
> -{
> -	return default_msi_mask_irq(desc, mask, flag);
> -}
> -
>  static void msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
>  {
> -	desc->masked = arch_msi_mask_irq(desc, mask, flag);
> +	desc->masked = __msi_mask_irq(desc, mask, flag);
>  }
>  
>  /*
> @@ -193,7 +188,7 @@ static void msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag)
>   * file.  This saves a few milliseconds when initialising devices with lots
>   * of MSI-X interrupts.
>   */
> -u32 default_msix_mask_irq(struct msi_desc *desc, u32 flag)
> +u32 __msix_mask_irq(struct msi_desc *desc, u32 flag)
>  {
>  	u32 mask_bits = desc->masked;
>  	unsigned offset = desc->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
> @@ -206,14 +201,9 @@ u32 default_msix_mask_irq(struct msi_desc *desc, u32 flag)
>  	return mask_bits;
>  }
>  
> -__weak u32 arch_msix_mask_irq(struct msi_desc *desc, u32 flag)
> -{
> -	return default_msix_mask_irq(desc, flag);
> -}
> -
>  static void msix_mask_irq(struct msi_desc *desc, u32 flag)
>  {
> -	desc->masked = arch_msix_mask_irq(desc, flag);
> +	desc->masked = __msix_mask_irq(desc, flag);
>  }
>  
>  static void msi_set_mask_bit(struct irq_data *data, u32 flag)
> @@ -852,7 +842,7 @@ void pci_msi_shutdown(struct pci_dev *dev)
>  	/* Return the device with MSI unmasked as initial states */
>  	mask = msi_mask(desc->msi_attrib.multi_cap);
>  	/* Keep cached state to be restored */
> -	arch_msi_mask_irq(desc, mask, ~mask);
> +	__msi_mask_irq(desc, mask, ~mask);

If I am reading this right, it will call the old 'default_msi_mask_irq'
which is exactly what we don't want to do under Xen. We want to call
the NOP code.
>  
>  	/* Restore dev->irq to its default pin-assertion irq */
>  	dev->irq = desc->msi_attrib.default_irq;
> @@ -950,7 +940,7 @@ void pci_msix_shutdown(struct pci_dev *dev)
>  	/* Return the device with MSI-X masked as initial states */
>  	list_for_each_entry(entry, &dev->msi_list, list) {
>  		/* Keep cached states to be restored */
> -		arch_msix_mask_irq(entry, 1);
> +		__msix_mask_irq(entry, 1);

Ditto here.

Looking more at this code I have to retract my Reviewed-by and Tested-by
on the whole series.

Is it possible to get a git tree for this please?

>  	}
>  
>  	msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 45ef8cb..cc46a62 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -19,6 +19,8 @@ void read_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
>  void get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
>  void __write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
>  void write_msi_msg(unsigned int irq, struct msi_msg *msg);
> +u32 __msix_mask_irq(struct msi_desc *desc, u32 flag);
> +u32 __msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag);
>  
>  struct msi_desc {
>  	struct {
> @@ -59,8 +61,8 @@ void arch_restore_msi_irqs(struct pci_dev *dev);
>  
>  void default_teardown_msi_irqs(struct pci_dev *dev);
>  void default_restore_msi_irqs(struct pci_dev *dev);
> -u32 default_msi_mask_irq(struct msi_desc *desc, u32 mask, u32 flag);
> -u32 default_msix_mask_irq(struct msi_desc *desc, u32 flag);
> +#define default_msi_mask_irq	__msi_mask_irq
> +#define default_msix_mask_irq	__msix_mask_irq
>  
>  struct msi_chip {
>  	struct module *owner;
> -- 
> 1.7.1
>