Re: x86: asm doubt

[Jeremy Fitzhardinge]

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.

   J

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