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

On Dec 7, 2007 12:50 AM, Yinghai Lu <yhlu.kernel@xxxxxxxxx> wrote:

On Dec 6, 2007 4:33 PM, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> 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
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