Re: [RFC PATCH v3 2/2] arm: kernel: fix pci_mmap_page_range() offset calculation

[Lorenzo Pieralisi]

On Fri, Jan 23, 2015 at 11:59:11PM +0000, Bjorn Helgaas wrote:
> On Thu, Nov 13, 2014 at 11:19:16AM +0000, Lorenzo Pieralisi wrote:
> > The pci_mmap_page_range() API should be written to expect offset
> > values representing PCI memory resource addresses as seen by user
> > space, through the pci_resource_to_user() API.
> > 
> > ARM relies on the standard implementation of pci_resource_to_user()
> > which actually is an identity map and exports to user space
> > PCI memory resources as they are stored in PCI devices resources
> > structures, which represent CPU physical addresses (fixed-up using
> > BUS to CPU address conversions) not PCI bus addresses.
> > 
> > Therefore, on ARM platforms where the mapping between CPU and BUS
> > address is not a 1:1 the current pci_mmap_page_range() implementation is
> > erroneous, in that an additional shift is applied to an already fixed-up
> > offset passed from userspace.
> > 
> > Hence, this patch removes the mem_offset from the pgoff calculation
> > since the offset as passed from user space already represents the CPU
> > physical address corresponding to the resource to be mapped, ie no
> > additional offset should be applied.
> > 
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> 
> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

Thank you, I will ask Russell to merge it.

Lorenzo

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