Re: [PATCH] kexec: force x86_64 arches to boot kdump kernels on boot cpu

["Yinghai Lu" <yhlu.kernel@gmail.com>]

On Dec 7, 2007 12:50 AM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
>
> On Dec 6, 2007 4:33 PM, Eric W. Biederman <ebiederm@xmission.com> wrote:
...
> >
> > 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.

it should be bit 18 (HTTC_APIC_EXT_ID)


YH