Hi,
I would appreciate if someone explains the reason for enabling LINT0 during
APIC reset. This does not correspond with Intel SDM Figure 10-8: “Local
Vector Table” that says all LVT registers are reset to 0x10000.
In kvm_lapic_reset, I see:
apic_set_reg(apic, APIC_LVT0,
SET_APIC_DELIVERY_MODE(0, APIC_MODE_EXTINT));
Which is actually pretty similar to QEMU’s apic_reset_common:
if (bsp) {
/*
* LINT0 delivery mode on CPU #0 is set to ExtInt at initialization
* time typically by BIOS, so PIC interrupt can be delivered to the
* processor when local APIC is enabled.
*/
s->lvt[APIC_LVT_LINT0] = 0x700;
}
Yet, in both cases, I miss the point - if it is typically done by the BIOS,
why does QEMU or KVM enable it?
BTW: KVM seems to run fine without it, and I think setting it causes me
problems in certain cases.
Thanks,
Nadav--
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