Messages in this thread | | | Date | Sun, 30 Aug 2009 08:39:01 -0700 | From | Jesse Barnes <> | Subject | Re: [PATCH v2] SR-IOV: correct broken resource alignment calculations |
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On Fri, 28 Aug 2009 13:00:06 -0700 Chris Wright <chrisw@sous-sol.org> wrote:
> * Matthew Wilcox (matthew@wil.cx) wrote: > > On Fri, Aug 28, 2009 at 12:17:14PM -0700, Chris Wright wrote: > > > 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. > > 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 thin PCI specific layer over the generic > resource_alignment() function which is aware of the special nature of > VF BARs and does sorting and allocation based on the smaller alignment > requirement. > > I recognize that while resource_alignment is generic, it's basically a > PCI helper. An alternative to this patch is to add PCI VF BAR > specific information to struct resource. I opted for the extra layer > rather than adding such PCI specific information to struct resource. > This does have the slight downside that we don't cache the BAR size > and re-read for each alignment query (happens a small handful of > times during boot for each VF BAR). > > Signed-off-by: Chris Wright <chrisw@sous-sol.org> > Cc: Jesse Barnes <jbarnes@virtuousgeek.org> > Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Matthew Wilcox <matthew@wil.cx> > Cc: Yu Zhao <yu.zhao@intel.com> > Cc: stable@kernel.org
Yeah, I like this one better. I've applied it to my for-linus branch; would be nice to have a Tested-by for it before I send it to Linus...
Thanks, -- Jesse Barnes, Intel Open Source Technology Center
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