> On Thu, Dec 06, 2007 at 07:10:23PM -0500, Neil Horman wrote:
> > On Thu, Dec 06, 2007 at 05:11:43PM -0500, Vivek Goyal wrote:
> > > On Thu, Dec 06, 2007 at 04:39:51PM -0500, Neil Horman wrote:
> > > > On Fri, Nov 30, 2007 at 09:51:31AM -0500, Neil Horman wrote:
> > > > > On Fri, Nov 30, 2007 at 09:42:50AM -0500, Vivek Goyal wrote:
> > > > <snip>
> > > > >
> > > > > Thats what I'm doing at the moment. I'm working on a RHEL5 patch at the moment
> > > > > (since thats whats on the production system thats failing), and will forward
> > > > > port it once its working
> > > > >
> > > > > And not to split hairs, but techically thats not our _only_ choice. We could
> > > > > force kdump boots on cpu0 as well ;)
> > > > >
> > > > > Thanks
> > > > > Neil
> > > > >
> > > > > > Thanks
> > > > > > Vivek
> > > > >
> > > >
> > > >
> > > > Sorry to have been quiet on this issue for a few days. Interesting news to
> > > > report, though. So I was working on a patch to do early apic enabling on
> > > > x86_64, and had something working for the old 2.6.18 kernel that we were
> > > > origionally testing on. Unfortunately while it worked on 2.6.18 it failed
> > > > miserably on 2.6.24-rc3-mm2, causing check_timer to consistently report that the
> > > > timer interrupt wasn't getting received (even though we could successfully run
> > > > calibrate_delay). Vivek and I were digging into this, when I ran accross the
> > > > description of the hypertransport configuration register in the opteron
> > > > specification. It contains a bit that, suprise, configures the ht bus to either
> > > > unicast interrupts delivered accross the ht bus to a single cpu, or to broadcast
> > > > it to all cpus. Since it seemed more likely that the 8259 in the nvidia
> > > > southbridge was transporting legacy mode interrupts over the ht bus than
> > > > directly to cpu0 via an actual wire, I wrote the attached patch to add a quirk
> > > > for nvidia chipsets, which scanned for hypertransport controllers, and ensured
> > > > that that broadcast bit was set. Test results indicate that this solves the
> > > > problem, and kdump kernels boot just fine on the affected system.
> > > >
> > >
> > > Hi Neil,
> > >
> > > Should we disable this broadcasting feature once we are through? Otherwise
> > > in normal systems it might mean extra traffic on hypertransport. There
> > > is no need for every interrupt to be broadcasted in normal systems?
> > >
> > > Thanks
> > > Vivek
> >
> > No, I don't think thats necessecary. Once the apics are enabled, interrupts
> > shouldn't travel accross the hypertransport bus anyway, opting instead to use
> > the dedicated apic bus (at least thats my understanding).
>
> I think all interrupt message travel on hypertransport. Even after APICS
> have been enabled.
>
> Look at the following document.
>
>
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/24674.pdf
>
> Have a look at figure 1, figure 2 and section 3.4.2.2 and 3.4.2.3
>
> That's a different thing that once IOAPIC has formed the vectored message,
> Hypertransport might not touch the destination field.
>
