Virtualization - Aug 2021 - [PATCH v4 09/15] pci: Consolidate pci_iomap* and pci_iomap*wc

Is there a branch with all of this applied?  I was going to apply this
to help take a look at it, but it doesn't apply to v5.14-rc1.  I know
you listed some prereqs in the cover letter, but it's a fair amount of
work to sort all that out.

On Wed, Aug 04, 2021 at 05:52:12PM -0700, Kuppuswamy Sathyanarayanan
wrote:
> From: Andi Kleen <ak at linux.intel.com>
If I were applying these, I would silently update the subject lines to
match previous commits.  Since these will probably be merged via a
different tree, you can update if there's a v5:

  PCI: Consolidate pci_iomap_range(), pci_iomap_wc_range()

Also applies to 11/15 and 12/15.
> pci_iomap* and pci_iomap*wc are currently duplicated code, except
> that the _wc variant does not support IO ports. Replace them
> with a common helper and a callback for the mapping. I used
> wrappers for the maps because some architectures implement ioremap
> and friends with macros.
Maybe spell some of this out:

  pci_iomap_range() and pci_iomap_wc_range() are currently duplicated
  code, ...  Implement them using a common helper,
  pci_iomap_range_map(), ...

Using "pci_iomap*" obscures the name and doesn't save any space.

Why is it safe to make pci_iomap_wc_range() support IO ports when it
didn't before?  That might be desirable, but I think it *is* a
functional change here.

IIUC, pci_iomap_wc_range() on an IO port range previously returned
NULL, and after this patch it will work the same as pci_iomap_range(),
i.e., it will return the result of __pci_ioport_map().
> This will allow to add more variants without excessive code
> duplications. This patch should have no behavior change.
> 
> Signed-off-by: Andi Kleen <ak at linux.intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy at
linux.intel.com>
> ---
>  lib/pci_iomap.c | 81 +++++++++++++++++++++++++++----------------------
>  1 file changed, 44 insertions(+), 37 deletions(-)
> 
> diff --git a/lib/pci_iomap.c b/lib/pci_iomap.c
> index 2d3eb1cb73b8..6251c3f651c6 100644
> --- a/lib/pci_iomap.c
> +++ b/lib/pci_iomap.c
> @@ -10,6 +10,46 @@
>  #include <linux/export.h>
>  
>  #ifdef CONFIG_PCI
> +
> +/*
> + * Callback wrappers because some architectures define ioremap et.al.
> + * as macros.
> + */
> +static void __iomem *map_ioremap(phys_addr_t addr, size_t size)
> +{
> +	return ioremap(addr, size);
> +}
> +
> +static void __iomem *map_ioremap_wc(phys_addr_t addr, size_t size)
> +{
> +	return ioremap_wc(addr, size);
> +}
> +
> +static void __iomem *pci_iomap_range_map(struct pci_dev *dev,
> +					 int bar,
> +					 unsigned long offset,
> +					 unsigned long maxlen,
> +					 void __iomem *(*mapm)(phys_addr_t,
> +							       size_t))
> +{
> +	resource_size_t start = pci_resource_start(dev, bar);
> +	resource_size_t len = pci_resource_len(dev, bar);
> +	unsigned long flags = pci_resource_flags(dev, bar);
> +
> +	if (len <= offset || !start)
> +		return NULL;
> +	len -= offset;
> +	start += offset;
> +	if (maxlen && len > maxlen)
> +		len = maxlen;
> +	if (flags & IORESOURCE_IO)
> +		return __pci_ioport_map(dev, start, len);
> +	if (flags & IORESOURCE_MEM)
> +		return mapm(start, len);
> +	/* What? */
> +	return NULL;
> +}
> +
>  /**
>   * pci_iomap_range - create a virtual mapping cookie for a PCI BAR
>   * @dev: PCI device that owns the BAR
> @@ -30,22 +70,8 @@ void __iomem *pci_iomap_range(struct pci_dev *dev,
>  			      unsigned long offset,
>  			      unsigned long maxlen)
>  {
> -	resource_size_t start = pci_resource_start(dev, bar);
> -	resource_size_t len = pci_resource_len(dev, bar);
> -	unsigned long flags = pci_resource_flags(dev, bar);
> -
> -	if (len <= offset || !start)
> -		return NULL;
> -	len -= offset;
> -	start += offset;
> -	if (maxlen && len > maxlen)
> -		len = maxlen;
> -	if (flags & IORESOURCE_IO)
> -		return __pci_ioport_map(dev, start, len);
> -	if (flags & IORESOURCE_MEM)
> -		return ioremap(start, len);
> -	/* What? */
> -	return NULL;
> +	return pci_iomap_range_map(dev, bar, offset, maxlen,
> +				   map_ioremap);
>  }
>  EXPORT_SYMBOL(pci_iomap_range);
>  
> @@ -70,27 +96,8 @@ void __iomem *pci_iomap_wc_range(struct pci_dev *dev,
>  				 unsigned long offset,
>  				 unsigned long maxlen)
>  {
> -	resource_size_t start = pci_resource_start(dev, bar);
> -	resource_size_t len = pci_resource_len(dev, bar);
> -	unsigned long flags = pci_resource_flags(dev, bar);
> -
> -
> -	if (flags & IORESOURCE_IO)
> -		return NULL;
> -
> -	if (len <= offset || !start)
> -		return NULL;
> -
> -	len -= offset;
> -	start += offset;
> -	if (maxlen && len > maxlen)
> -		len = maxlen;
> -
> -	if (flags & IORESOURCE_MEM)
> -		return ioremap_wc(start, len);
> -
> -	/* What? */
> -	return NULL;
> +	return pci_iomap_range_map(dev, bar, offset, maxlen,
> +				   map_ioremap_wc);
>  }
>  EXPORT_SYMBOL_GPL(pci_iomap_wc_range);
>  
> -- 
> 2.25.1
>

> Why is it safe to make pci_iomap_wc_range() support IO ports when it
> didn't before?  That might be desirable, but I think it *is* a
> functional change here.
None of the callers use it to map IO ports, so it will be a no-op for 
them. But you're right, it's a (minor) functional change.

-Andi