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[Xen-ia64-devel] Strange code in vmx_ivt.S

from [tgingold]

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Subject:	[Xen-ia64-devel] Strange code in vmx_ivt.S
From:	tgingold@xxxxxxx
Date:	Sun, 3 Jun 2007 23:48:55 +0200
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Hi,

can someone (from Intel ?) comment this code:

// 0x0c00 Entry 3 (size 64 bundles) Alt ITLB (19)
ENTRY(vmx_alt_itlb_miss)
    VMX_DBG_FAULT(3)
    mov r31 = pr
    mov r29=cr.ipsr;
    ;;
    tbit.z p6,p7=r29,IA64_PSR_VM_BIT;
(p7)br.spnt vmx_fault_3
vmx_alt_itlb_miss_1:
    mov r16=cr.ifa    // get address that caused the TLB miss
    ;;
    tbit.z p6,p7=r16,63  //*********************************
(p6)br.spnt vmx_fault_3
    ;;

I don't understand the tbit.z (***) test.  The code after the br does itc
in identity-mapped area.  But testing bit 63 is not enough.

Tristan.

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