From owner-freebsd-ia64@FreeBSD.ORG  Fri Jan 28 11:54:36 2005
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Date: Fri, 28 Jan 2005 12:53:17 +0100
From: Christian Hildner <christian.hildner@hob.de>
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Subject: TLB miss handlers
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Hi,

looking at entry 0x0400 of the interrupt table I am wondering about the 
following lines:

IVT_ENTRY(Instruction_TLB, 0x0400)
    mov r16=cr.ifa
    mov r17=pr
    ;;
    thash   r18=r16
    ttag    r19=r16
    ;;
    add r21=16,r18      // tag
    add r20=24,r18      // collision chain
    ;;
    ld8 r21=[r21]       // check VHPT tag
    ^^^^^^^^^^
Are you sure you cannot enter a nested TLB miss fault here on IA64 
implementations that do not have the VHPT walker implemented? You 
wouldn't get fault 0x0000 since there is no walker that throws that fault.

Christian