[SeaBIOS] [seabios PATCH 1/2] acpi: set I/O APIC ID to 0 by default

[Eduardo Habkost]

On Mon, Jul 23, 2012 at 02:42:27PM +0300, Gleb Natapov wrote:
> On Fri, Jul 20, 2012 at 01:22:43PM -0300, Eduardo Habkost wrote:
> > 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].
> > 
> http://www.intel.com/design/chipsets/datashts/29056601.pdf says that it
> should be programmed to unique value. I checked 4 machines on 3 of them
> this was the case on one (AMD) there are 3 IOAPICs and they all overlap with
> APICs.

True, but it says "All APIC devices using the APIC bus". Figure 10-1 on
Intel SDM Volume 3 makes me believe the I/O APIC and Local APICs are not
connected to the same APIC bus since Pentium 4.

Anyway, if anybody wants to patch SeaBIOS to guarantee the I/O APIC ID
not conflict with the Local APICs, it would be welcome. While this is
not done, the ACPI tables need to match reality.

(The MP-Table has to be changed too, I will send a new patch soon.
Thanks for pointing that out).

> 
> > 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.
> > 
> The currant code was written when we could only dream supporting 16 cpus
> and back than it did correct thing, but now it just broken. QEMU do not
> care about IOAPIC ID for sure so I am OK with the patch.
> > 
> > [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.
> 1 from 4 for me :)
> 
> > 
> > > 
> > > > Signed-off-by: Eduardo Habkost <ehabkost at 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
> 
> --
> 			Gleb.
> 

-- 
Eduardo