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    SubjectRe: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu
    Eric W. Biederman wrote:
    > Neil Horman <nhorman@redhat.com> writes:
    >
    >>> ..TIMER: vector=0x31 apic1=0 pin1=2 apic2=-1 pin2=-1
    >
    > Ben, what chipset is this?

    nVidia MCP55 pro

    It is the original version of
    http://www.supermicro.com/Aplus/motherboard/Opteron8000/MCP55/H8QM8-2.cfm

    i.e. not the -2. However, they don't seem to advertise the original
    version. Supermicro assures me that they are practically the same but I
    haven't played with the -2 version yet.


    >
    >> Ok, I think from what I understand of what we're reading here, the apic2 = -1
    >> and pin2 = -1 indicate that the 8259 has no direct connection to any cpu, which
    >> means that on shutdown disable_IO_APIC should take us into virtual wire mode.
    >> As such enabling the APIC early in boot should fix us, but more consisely,
    >> rewriting the entry in the IOAPIC to deliver int0 to the only running cpu should
    >> accomplish the same goal for this problem. Does that sound reasonable (at least
    >> as a test to ensure we understand the problem) to everyone?
    >
    > Close. There are two options with virtual wire mode.
    > - Either the local apic is in virtual wire mode, and somehow the
    > legacy interrupts make it to the local cpu.
    > - Or an ioapic is in virtual wire mode and the legacy interrupt
    > controller is connected to it.
    >
    > So I guess fundamentally for any SMP system that only supports the
    > cpu being in local apic mode and only routes interrupts to the boot
    > strap processor we could be in trouble. That is what our current
    > information about your system suggests.
    >
    > However most systems actually connect the i8254 PIC interrupt
    > controller to the ioapic in virtual wire mode. As I recall the
    > standard mapping is to ioapic 0, pin 0. With ioapic 0, pin 2 being
    > the timer interrupt (Possibly it is the other way around).
    >
    > So as a test we could feed those values into ioapic_8259 and see
    > if the kdump case works. I believe we prefer putting the ioapic
    > into virtual wire mode over putting the cpu into virtual wire
    > mode. We can only control which cpu receives the legacy interrupts if
    > we are putting the ioapic in virtual wire mode.
    >
    > It may also be an interesting test to just enable the timer for the
    > ioapic in early boot, as you have suggested. I don't have a clue what
    > that will do.
    >
    > Eric
    >
    > _______________________________________________
    > kexec mailing list
    > kexec@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/kexec


    --
    -ben
    -=-
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