Re: [Xen-devel] [PATCH] support protected mode mmio with non-zero CS base

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 22/11/06 7:36 am, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> Remove the "if ( realmode ) " and just use the segment base address. The
>> base-address in the register should be correct even in realmod, or the
>> processor is broken. [I don't think this code is being executed from
>> vmxassist - if it is, then that's a different special case!].
> 
> I intentionally didn't, as at least on VMX the read operation could
> be significantly slower than a shift (and due to the indirect call it will
> be slower even on SVM).

We'll be using the segment base info everywhere in future, otherwise big
real mode does not work. Also, realmode is going to be the uncommon case by
far here (and we don't care that much for its performance as long as it
doesn't noticeably suck too badly).

 -- Keir



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