Re: [Xen-devel] [PATCH] x86emul: drop dead code from SYSENTER handling

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/12/16 14:02, Jan Beulich wrote:
> There's no point reading CS - all of the fields get set from scratch
> right afterwards. Also correct a wrong comment.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although

>
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -4841,12 +4841,10 @@ x86_emulate(
>  
>          _regs.eflags &= ~(EFLG_VM | EFLG_IF | EFLG_RF);
>  
> -        fail_if(ops->read_segment == NULL);
> -        ops->read_segment(x86_seg_cs, &cs, ctxt);
>          cs.sel = msr_content & ~3; /* SELECTOR_RPL_MASK */
>          cs.base = 0;   /* flat segment */
>          cs.limit = ~0u;  /* 4GB limit */
> -        cs.attr.bytes = lm ? 0xa9b  /* L+DB+P+S+Code */
> +        cs.attr.bytes = lm ? 0xa9b  /* L+G+P+S+Code */

Strictly speaking its G+L+P, seeing as the other attributes are listed
in bit order.

~Andrew

>                             : 0xc9b; /* G+DB+P+S+Code */
>  
>          sreg.sel = cs.sel + 8;
>
>
>


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