On Dec 6, 2007 4:33 PM, Eric W. Biederman <ebiederm at xmission.com> wrote: > Vivek Goyal <vgoyal at redhat.com> writes: > > > > 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? > > My feel is that if it is for legacy interrupts only it should not be a problem. > Let's investigate and see if we can unconditionally enable this quirk > for all opteron systems. i checked that bit http://www.openbios.org/viewvc/trunk/LinuxBIOSv2/src/northbridge/amd/amdk8/coherent_ht.c?revision=2596&view=markup static void enable_apic_ext_id(u8 node) { #if ENABLE_APIC_EXT_ID==1 #warning "FIXME Is the right place to enable apic ext id here?" u32 val; val = pci_read_config32(NODE_HT(node), 0x68); val |= (HTTC_APIC_EXT_SPUR | HTTC_APIC_EXT_ID | HTTC_APIC_EXT_BRD_CST); pci_write_config32(NODE_HT(node), 0x68, val); #endif } that bit only be should be set when apic id is lifted and cpu apid is using 8 bits and that mean broadcast is 0xff instead 0x0f. for example 8 socket dual core system or 4 socket quad core system,that you should make BSP start from 0x04, so cpus apic id will be [0x04, 0x13) So if you want to enable that in early_quirk, you need to make sure apic id is using 8 bits by check if the bit 16 (HTTC_APIC_ID) is set. most BIOS already did that. You may ask Supermicro fix their broken BIOS instead. YH
