On Fri, Jul 20, 2012 at 12:18:59AM +0300, Gleb Natapov wrote: > On Thu, Jul 19, 2012 at 05:52:41PM -0300, Eduardo Habkost wrote: > > When resetting an I/O APIC, its ID is set to 0, so set it to 0 on the > > MADT table too. > > > Actually BIOS needs to configure ioapic id to a uniqe value. This does > not really matter for KVM though.
Where does this requirement comes from? I am guessing it matters only when the I/O APIC is directly connected to the APIC bus (according to Intel SDM, that's the case only for old Pentium and P6 CPUs)[1]. Anyway, even if some hardware has this unique-ID requirement, today Seabios does not fulfill it, leaving the I/O APIC ID as 0. The patch at least makes the MADT table match reality. [1] I have checked 3 different machines, and all machines I have looked have an I/O APIC ID that conflicts with an existing Local APIC ID, on the ACPI MADT table. Some iasl dumps may be found online by googling for: "Subtable Type : 01" "I/O Apic ID" I looked at 5 or 6 matches, and almost every one have an I/O APIC ID conflicting with a Local APIC ID. > > > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> > > --- > > src/acpi.c | 2 +- > > src/config.h | 2 ++ > > 2 files changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/src/acpi.c b/src/acpi.c > > index 55e4607..3f55de9 100644 > > --- a/src/acpi.c > > +++ b/src/acpi.c > > @@ -335,7 +335,7 @@ build_madt(void) > > struct madt_io_apic *io_apic = (void*)apic; > > io_apic->type = APIC_IO; > > io_apic->length = sizeof(*io_apic); > > - io_apic->io_apic_id = CountCPUs; > > + io_apic->io_apic_id = BUILD_IOAPIC_ID; > > io_apic->address = cpu_to_le32(BUILD_IOAPIC_ADDR); > > io_apic->interrupt = cpu_to_le32(0); > > > > diff --git a/src/config.h b/src/config.h > > index 3a70867..878c691 100644 > > --- a/src/config.h > > +++ b/src/config.h > > @@ -52,9 +52,11 @@ > > #define BUILD_PCIMEM64_END 0x10000000000ULL > > > > #define BUILD_IOAPIC_ADDR 0xfec00000 > > +#define BUILD_IOAPIC_ID 0 > > #define BUILD_HPET_ADDRESS 0xfed00000 > > #define BUILD_APIC_ADDR 0xfee00000 > > > > + > > // Important real-mode segments > > #define SEG_IVT 0x0000 > > #define SEG_BDA 0x0040 > > -- > > 1.7.10.4 > > -- > Gleb. > -- Eduardo