Re: [patch] (big) real mode emulation - mov rl/rh/r

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Avi Kivity wrote:
> Nitin A Kamble wrote:
>> On Tue, 2007-10-30 at 18:06 -0700, Avi Kivity wrote:
>>  
>>> Nitin A Kamble wrote:
>>>    
>>>> Hi Avi,
>>>>   Attached is the patch to implement emulation of instructions
>>>>   mov rl, imm8 (opcodes 0xb0-0xb3)
>>>>   mov rh, imm8 (opcodes 0xb4-0xb7)
>>>>   mov r, imm (opcodes0xb8-0xbf)
>>>>
>>>>  
>>>> @@ -146,8 +146,12 @@ static u16 opcode_table[256] = {
>>>>         0, 0, ByteOp | ImplicitOps | Mov, ImplicitOps | Mov,
>>>>         ByteOp | ImplicitOps | Mov, ImplicitOps | Mov,
>>>>         ByteOp | ImplicitOps, ImplicitOps,
>>>> -       /* 0xB0 - 0xBF */
>>>> -       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>>>> +       /* 0xB0 - 0xB7 */
>>>> +       Mov | SrcImmByte, Mov | SrcImmByte, Mov | SrcImmByte, Mov |
>>>> SrcImmByte,
>>>> +       Mov | SrcImmByte, Mov | SrcImmByte, Mov | SrcImmByte, Mov |
>>>> SrcImmByte,
>>>> +       /* 0xB8 - 0xBF */
>>>> +       Mov | SrcImm, Mov | SrcImm, Mov | SrcImm, Mov | SrcImm,
>>>> +       Mov | SrcImm, Mov | SrcImm, Mov | SrcImm, Mov | SrcImm,
>>>>         /* 0xC0 - 0xC7 */
>>>>       
>>> Perhaps adding DstReg would reduce the decoding code later on?
>>>     
>>
>> Avi,
>> The decoding of register is significantly different for these
>> instructions. It will be just moving code from one place to other place.
>>
>>   
>
> Right.
>
> But perhaps we can have a ShortReg modifier to make the decoding 
> common.  There are several instructions which can use this (inc, dec, 
> xchg, push, mov).
>
> I'll look into this.
>

I've committed a few patches which enable this.  Now, a DstReg or SrcReg 
without ModRM will decode the opcode byte to get the register.  It also 
fixes a minor issue with ignoring rex prefixes on 64-bit byte insns. 
mov, inc, dec, push, and pop have been converted.

Please review these patches carefully as I haven't been able to give 
them a real workout other than booting a few guests.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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