Re: [PATCH 1/5] KVM: x86 emulator: Use single stage decoding for Group 1 instructions

[Avi Kivity <avi@redhat.com>]

On 03/15/2011 04:06 PM, Takuya Yoshikawa wrote:
> >  >  So I just decided to treat CMPS and SCAS in another patch.
> >  >  I mean I may introduce em_cmps or em_scas later if needed.
> >  >
> >  scas will likely just call em_cmp.
> >
> >  >  You prefer to treat these in this patch?
> >  >
> >  If there will be other patch for those instruction then it may be left
> >  as is.
>
> In my city, electric power supply may become restricted under control
> from now, though only a few hours.  So please take the patch series as
> is if possible!

I prefer to have the patchset fully updated, even if it takes a while.  
Good luck with the recovery!

> >  >
> >  >  What is the difference of CMPS and SCAS?
> >  >
> >  >
> >  One compares to memory locations and another memory with AX register.
>
> I wanted to know whether we should introduce em_cmps() or em_scas() later.
>
> Probably we can eliminate introducing em_scas() because it should be
> completely same as em_cmp().

I agree.

> But em_cmps() will be needed for inserting
>    c->dst.type = OP_NONE;
> before em_cmp().

I think we can put this line into em_cmp().  In fact, it looks like CMP 
r/m, reg will now write back the data into memory, which is wrong.  So I 
recommend a first patch to add c->dst.type = OP_NONE before the cmp: 
label, so we have a fix patch followed by a refactoring patch.

Later we can have a ReadOnly opcode table bit, so we can disable 
writeback from the opcode tables, not the code.


-- 
error compiling committee.c: too many arguments to function