On Fri, 28 Aug 2009 13:00:06 -0700 Chris Wright <chrisw@xxxxxxxxxxxx> wrote: > * Matthew Wilcox (matthew@xxxxxx) 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@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 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
