lkml.org 
[lkml]   [2009]   [Aug]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] SR-IOV: correct broken resource alignment calculations
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.

Yes, I think that would be preferable. We have a *LOT* of resources in
the kernel, and the embedded folks would not find it funny if they all
grew in size suddenly.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."


\
 
 \ /
  Last update: 2009-08-28 21:51    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site