Messages in this thread |  | | | Date | Wed, 09 Jun 2010 09:23:44 -0500 | | From | Mike Habeck <> | | Subject | Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already assigned |
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Jesse Barnes wrote: > On Tue, 08 Jun 2010 17:53:19 -0700 > "H. Peter Anvin" <hpa@zytor.com> wrote: > >> On 06/02/2010 08:53 AM, Jesse Barnes wrote: >>>> That's what I thought, which I guess means my original question to Mike >>>> still stands... >>> I thought the whole reason for this was hotplug; we don't want to >>> exhaust I/O space unnecessarily by allocating resources for BARs the >>> BIOS didn't assign so we can keep them around for later hotplug >>> activity. >>> >>> If there's some other issue, it's not too late to drop this patch. >>> >> Okay, now... this means that if a device that the BIOS doesn't know >> about, but which needs I/O addresses, then it will work if hotplugged, >> but not if it is plugged in on system boot? > > Depends on the BIOS interactions on this platform; if the kernel ends > up doing all the allocations itself, we'll allocate space for every BAR > unconditionally, meaning that any hotplugged device should work.
Correct, our BIOS allocates I/O space for all devices except for a few that it knows don't use it. On a hotplug attach the kernel will be unconditionally allocating the I/O space for all devices.. The pci=nobar option strictly prevents the kernel from allocating BAR resources to device BARs that the BIOS didn't assign (similar to how the pci=norom option works for the device's ROM BAR)
> > But really the SGI guys should comment here. >
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