Subject: Re: Missing operand for tlbie instruction on Power7

From: Laura Abbott <[email-masked]>
Date: Fri, 2 Oct 2015 15:12:08 -0700

On 10/02/2015 03:00 PM, Segher Boessenkool wrote:
> On Sat, Oct 03, 2015 at 12:37:35AM +0300, Denis Kirjanov wrote:
>>>> -0:     tlbie   r4;                             \
>>>> +0:     tlbie   r4, 0;                          \
>>>
>>> This isn't correct.  With POWER7 and later (which this compile
>>> is, since it's on LE), the tlbie instruction takes two register
>>> operands:
>>>
>>>      tlbie RB, RS
>>>
>>> The tlbie instruction on pre POWER7 cpus had one required register
>>> operand (RB) and an optional second L operand, where if you omitted
>>> it, it was the same as using "0":
>>>
>>>      tlbie RB, L
>>>
>>> This is a POWER7 and later build, so your change which adds the "0"
>>> above is really adding r0 for RS.  The new tlbie instruction doesn't
>>> treat r0 specially, so you'll be using whatever random bits which
>>> happen to be in r0 which I don't think that is what you want.
>>
>> Ok, than we can just zero out r5 for example and use it in tlbie as RS,
>> right?
>
> That won't assemble _unless_ your assembler is in POWER7 mode.  It also
> won't do the right thing at run time on older machines.
>
> Where is this tlbia macro used at all, for 64-bit machines?
>

[labbott@labbott-redhat-machine linux_upstream]$ make ARCH=powerpc CROSS_COMPILE=powerpc64-linux-gnu-
   CHK     include/config/kernel.release
   CHK     include/generated/uapi/linux/version.h
   CHK     include/generated/utsrelease.h
   CHK     include/generated/bounds.h
   CHK     include/generated/timeconst.h
   CHK     include/generated/asm-offsets.h
   CALL    scripts/checksyscalls.sh
   CHK     include/generated/compile.h
   CALL    arch/powerpc/kernel/systbl_chk.sh
   AS      arch/powerpc/kernel/swsusp_asm64.o
arch/powerpc/kernel/swsusp_asm64.S: Assembler messages:
arch/powerpc/kernel/swsusp_asm64.S:188: Error: missing operand
scripts/Makefile.build:294: recipe for target 'arch/powerpc/kernel/swsusp_asm64.o' failed
make[1]: *** [arch/powerpc/kernel/swsusp_asm64.o] Error 1
Makefile:941: recipe for target 'arch/powerpc/kernel' failed
make: *** [arch/powerpc/kernel] Error 2

This is piece of code protected by CONFIG_PPC_BOOK3S_64.
  
> Segher