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    SubjectRe: x86: asm doubt
    Avi Kivity wrote:
    > Jeremy Fitzhardinge wrote:
    >> In 32-bit mode, moving to a segment register can fault if the
    >> underlying GDT/LDT entry is invalid. In 64-bit mode, segment
    >> registers are mostly decorative and have no function, and moving
    >> arbitrary values into them doesn't fault, making the exception
    >> catching unnecessary.
    > 64-bit mode will in fact fault if an access is made outside the
    > GDT/LDT, or of the descriptor is invalid.

    Oh, I didn't think it bothered. I guess I'm conflating that with the
    fact that it doesn't apply any of the segment properties to memory
    accesses. Anyway, in that case the 64-bit code should definitely be
    using the standard segment accessors.


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