WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-ia64-devel

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

To: <tgingold@xxxxxxx>, "Xen-ia64-devel" <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-ia64-devel] Strange code in vmx_ivt.S
From: "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Date: Mon, 4 Jun 2007 09:19:45 +0800
Delivery-date: Sun, 03 Jun 2007 18:17:52 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <20070603214855.GA1939@xxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-ia64-devel-request@lists.xensource.com?subject=help>
List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
List-post: <mailto:xen-ia64-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-ia64-devel>, <mailto:xen-ia64-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-ia64-devel>, <mailto:xen-ia64-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcemKEG06sWKBYHzSraJL6on5I9f6AAHcKPw
Thread-topic: [Xen-ia64-devel] Strange code in vmx_ivt.S
>
>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.

This code is used for early debug, and it will not branch.
The check can be removed.

Thanks,
Anthony

_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel

<Prev in Thread] Current Thread [Next in Thread>