Re: [PATCH v2 6/8] arm64: alternatives: have callbacks take a cap

[Jon Hunter <jonathanh@nvidia.com>]

On 29/09/2022 11:47, Mark Rutland wrote:
> On Thu, Sep 29, 2022 at 10:53:56AM +0100, Jon Hunter wrote:
>>
>> On 27/09/2022 10:31, Jon Hunter wrote:
>>
>> ...
>>
>>>> diff --git a/arch/arm64/include/asm/alternative-macros.h
>>>> b/arch/arm64/include/asm/alternative-macros.h
>>>> index 7e157ab6cd505..189c31be163ce 100644
>>>> --- a/arch/arm64/include/asm/alternative-macros.h
>>>> +++ b/arch/arm64/include/asm/alternative-macros.h
>>>> @@ -2,10 +2,16 @@
>>>>    #ifndef __ASM_ALTERNATIVE_MACROS_H
>>>>    #define __ASM_ALTERNATIVE_MACROS_H
>>>> +#include <linux/const.h>
>>>> +
>>>>    #include <asm/cpucaps.h>
>>>>    #include <asm/insn-def.h>
>>>> -#define ARM64_CB_PATCH ARM64_NCAPS
>>>> +#define ARM64_CB_BIT    (UL(1) << 15)
>>>> +
>>>> +#if ARM64_NCAPS >= ARM64_CB_BIT
>>>> +#error "cpucaps have overflown ARM64_CB_BIT"
>>>> +#endif
>>>
>>>
>>> Some of our builders are failing and bisect is pointing to this commit.
>>> Looks like they don't like the above and I see the following errors ...
>>>
>>>     CC      arch/arm64/kvm/hyp/vhe/debug-sr.o
>>> /tmp/ccY3kbki.s: Assembler messages:
>>> /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1600: Error: junk at end of line, first unrecognized
>>> character is `L'
>>> /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
>>> /tmp/ccY3kbki.s:1723: Error: junk at end of line, first unrecognized
>>> character is `L'
>>> scripts/Makefile.build:249: recipe for target
>>> 'arch/arm64/kvm/hyp/vhe/debug-sr.o' failed
>>>
>>> Seems that it does not like the 'UL' macro for some reason. Any thoughts?
>>
>>
>> FYI, this issue is seen with GCC6 but GCC7 and beyond appear to work fine.
> 
> Hmm... IIRC there was an issue with some older binutils here not liking the UL
> suffix, but I thought we'd moved beyond those versions now; can you tell me
> exactly which binutils version you're using?
> 
> I currently can't run the kernel.org crosstool GCC 5.5.0 release on my machine
> since something's going wrong looking for an older version of libisl.so than my
> system provides; I'll see if I can get that going and test locally.
> 
> I suspect we can bodge around this with something like the diff below.
> 
> Thanks,
> Mark.
> 
> ---->8----
> diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h
> index 966767debaa3..4dd23bdbfb9e 100644
> --- a/arch/arm64/include/asm/alternative-macros.h
> +++ b/arch/arm64/include/asm/alternative-macros.h
> @@ -2,12 +2,14 @@
>   #ifndef __ASM_ALTERNATIVE_MACROS_H
>   #define __ASM_ALTERNATIVE_MACROS_H
>   
> +#include <linux/bits.h>
>   #include <linux/const.h>
>   
>   #include <asm/cpucaps.h>
>   #include <asm/insn-def.h>
>   
> -#define ARM64_CB_BIT	(UL(1) << 15)
> +#define ARM64_CB_SHIFT	15
> +#define ARM64_CB_BIT	BIT(ARM64_CB_SHIFT)
>   
>   #if ARM64_NCAPS >= ARM64_CB_BIT
>   #error "cpucaps have overflown ARM64_CB_BIT"
> @@ -80,7 +82,7 @@
>   	__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
>   
>   #define ALTERNATIVE_CB(oldinstr, feature, cb) \
> -	__ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_BIT | (feature), 1, cb)
> +	__ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (feature), 1, cb)
>   #else
>   
>   #include <asm/assembler.h>
> @@ -150,7 +152,7 @@
>   .macro alternative_cb cap, cb
>   	.set .Lasm_alt_mode, 0
>   	.pushsection .altinstructions, "a"
> -	altinstruction_entry 661f, \cb, ARM64_CB_BIT | \cap, 662f-661f, 0
> +	altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
>   	.popsection
>   661:
>   .endm


Yes that fixes it.

Tested-by: Jon Hunter <jonathanh@nvidia.com>

Cheers
Jon

-- 
nvpublic