Re: [PATCH] SR-IOV: correct broken resource alignment calculations

[Greg KH]

On Fri, Aug 28, 2009 at 12:17:14PM -0700, Chris Wright wrote:
> An SR-IOV capable device includes an SR-IOV PCIe capability which
> describes the Virtual Function (VF) BAR requirements.  A typical SR-IOV
> device can support multiple VFs whose BARs must be in a contiguous region,
> effectively an array of VF BARs.  The BAR reports the size requirement
> for a single VF.  We calculate the full range needed by simply multiplying
> the VF BAR size with the number of possible VFs and create a resource
> spanning the full range.
> 
> This all seems sane enough except it artificially inflates the alignment
> requirement for the VF BAR.  The VF BAR need only be aligned to the size
> of a single BAR not the contiguous range of VF BARs.  This can cause us
> to fail to allocate resources for the BAR despite the fact that we
> actually have enough space.
> 
> This patch adds a support for a new resource alignment type,
> IORESOURCE_VSIZEALIGN, and allows struct resource to keep track of the
> size requirements of a VF BAR which are smaller than the full resource
> size.  This could also be done all within the PCI layer w/out bloating
> struct resource or using the last available bit for alignment types.
> 
> Comments?
> 
> Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
> Cc: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
> Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Matthew Wilcox <matthew@xxxxxx>
> Cc: Yu Zhao <yu.zhao@xxxxxxxxx>
> Cc: stable@xxxxxxxxxx

This is a new feature, which seems to be odd to have it sent to stable
:)

Does this fix reported problems in the "wild"?

Other than that minor procedural thing, the patch looks good to me.

thanks,

greg k-h
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