Re: [PATCH 4/5] KVM: x86: Wrong register masking in 64-bit mode

[Paolo Bonzini]

Il 07/05/2014 14:32, Nadav Amit ha scritto:
> 32-bit operations are zero extended in 64-bit mode. Currently, the code does
> not handle them correctly and keeps the high bits. In 16-bit mode, the high
> 32-bits are kept intact.
>
> In addition, although it is not well-documented, when address override prefix
> is used with REP-string instruction, RCX high half is zeroed even if ECX was
> zero on the first iteration (as if an assignment was performed to ECX).

Is this true even for REPZ and ZF=0 or REPNZ and ZF=1?

Paolo
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