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RE: [Xen-devel] hvm_decode() questions


  • To: "Jan Beulich" <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Li, Xin B" <xin.b.li@xxxxxxxxx>
  • Date: Fri, 24 Nov 2006 22:07:05 +0800
  • Delivery-date: Fri, 24 Nov 2006 06:07:18 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AccP0UBHCEAjTLwORv2rDuS/c6B3wAAAFShQ
  • Thread-topic: [Xen-devel] hvm_decode() questions

 

>1) single-byte opcode 0x87 (xchg): What is this strange conditional
>
>        if ( ((*(opcode+1)) & 0xc7) == 5 )
>
>supposed to address? xchg has absolutely symmetric operands.
>
>2) two-byte opcode 0xB7 (movzx): What is this dependency on rex
>bit 3 doing here? Apparently this was based on Intel's (broken)
>documentation - the source operand is always 16 bits.
>
>Unless someone can explain these, I'll send a patch to remove them.

I agree that hvm_decode needs a careful review.
-Xin

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