[Bugme-new] [Bug 4194] New: x86_64 genapic mechanism doesn't detect systems which always operate in physical APIC mode

[bugme-daemon at osdl.org]

http://bugme.osdl.org/show_bug.cgi?id=4194

           Summary: x86_64 genapic mechanism doesn't detect systems which
                    always operate in physical APIC mode
    Kernel Version: 2.6.10
            Status: NEW
          Severity: high
             Owner: len.brown at intel.com
         Submitter: jason at rightthere.net
                CC: protasnb at yahoo.com


Distribution: any which uses 2.6.10
Hardware Environment: ES7000 Servers
Software Environment: System initialization
Problem Description:
The current x86_64 genapic driver only enables the apic_cluster driver depending 
on the number of clusters counted. The 4 most significant bits of the APICID
determine a cluster #. For the install case, the current x86_64 genapic
algorithm will only recognize one CPU (hence one cluster) and will default to
the apic_flat driver, which uses logical APIC mode for interrupt delivery
destination. This solution is not satisfactory for systems, like Unisys’ ES7000
machines, which always use physical APIC mode regardless of how many
CPU/clusters are accounted for by the x86_64 genapic driver for interrupt
delivery destination.

The ACPI 3.0 specification introduces a new FADT feature flag called 
“FORCE_APIC_PHYSICAL_DESTINATION_MODE” which would help solve the physical APIC
detection problem in the x86_64 genapic mechanism. Currently, Linux’s ACPI
implementation is based off of the 2.0c specification and the flag of interest
resides in the reserved6 member of the fadt_descriptor_rev2 structure.

Steps to reproduce: Build a smp x86_64 kernel using standard smp config and boot.

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