On Fri, Nov 07, 2008 at 11:40:21AM +0800, Zhao, Yu wrote: > Greg KH wrote: >> On Fri, Nov 07, 2008 at 10:37:55AM +0800, Zhao, Yu wrote: >>> Greg KH wrote: >>>> On Wed, Oct 22, 2008 at 04:45:31PM +0800, Yu Zhao wrote: >>>>> Documentation/kernel-parameters.txt | 10 ++++++++++ >>>>> 1 files changed, 10 insertions(+), 0 deletions(-) >>>>> >>>>> diff --git a/Documentation/kernel-parameters.txt >>>>> b/Documentation/kernel-parameters.txt >>>>> index 53ba7c7..5482ae0 100644 >>>>> --- a/Documentation/kernel-parameters.txt >>>>> +++ b/Documentation/kernel-parameters.txt >>>>> @@ -1677,6 +1677,16 @@ and is between 256 and 4096 characters. It is >>>>> defined in the file >>>>> cbmemsize=nn[KMG] The fixed amount of bus space which is >>>>> reserved for the CardBus bridge's memory >>>>> window. The default value is 64 megabytes. >>>>> + assign-mmio=[dddd:]bb [X86] reassign memory resources of all >>>>> + devices under bus [dddd:]bb (dddd is the domain >>>>> + number and bb is the bus number). >>>>> + assign-pio=[dddd:]bb [X86] reassign io port resources of all >>>>> + devices under bus [dddd:]bb (dddd is the domain >>>>> + number and bb is the bus number). >>>>> + align-mmio=[dddd:]bb:dd.f [X86] relocate memory resources of a >>>>> + device to minimum PAGE_SIZE alignment (dddd is >>>>> + the domain number and bb, dd and f is the bus, >>>>> + device and function number). >>>> This seems like a big problem. How are we going to know to add these >>>> command line options for devices we haven't even seen/known about yet? >>>> How do we know the bus ids aren't going to change between boots (hint, >>>> they are, pci bus ids change all the time...) >>>> We need to be able to do this kind of thing dynamically, not fixed at >>>> boot time, which seems way to early to even know about this, right? >>>> thanks, >>>> greg k-h >>> Yes, I totally agree. Doing things dynamically is better. >>> >>> The purpose of these parameters is to rebalance and align resources for >>> device that has BARs encapsulated in various new capabilities (SR-IOV, >>> etc.), because most of existing BIOSes don't take care of those BARs. >> But how are you going to know what the proper device ids are going to >> be before the machine boots? I don't see how these options are ever >> going to work properly for a "real" user. >>> If we do resource rebalance after system is up, do you think there is any >>> side effect or impact to other subsystem other than PCI (e.g. MTRR)? >> I don't think so. >>> I haven't had much thinking on the dynamical resource rebalance. If you >>> have any idea about this, can you please suggest? >> Yeah, it's going to be hard :) >> We've thought about this in the past, and even Microsoft said it was >> going to happen for Vista, but they realized in the end, like we did a >> few years previously, that it would require full support of all PCI >> drivers as well (if you rebalance stuff that is already bound to a >> driver.) So they dropped it. >> When would you want to do this kind of rebalancing? Before any PCI >> driver is bound to any devices? Or afterwards? > > I guess if we want the rebalance dynamic, then we should have it full -- > the rebalance would be functional even after the driver is loaded. > > But in most cases, there will be problem when we unload driver from a hard > disk controller, etc. We can mount root on a ramdisk and do the rebalance > there, but it's complicated for a real user. > > So looks like doing rebalancing before any driver is bound to any device is > also a nice idea, if user can get a shell to do rebalance before built-in > PCI driver grabs device. That's not going to work, it needs to happen before any PCI device is bound, which is before init runs. thanks, greg k-h -- 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
