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

[Jon Hunter <jonathanh@nvidia.com>]

Hi Mark,

On 12/09/2022 17:22, Mark Rutland wrote:
> Today, callback alternatives are special-cased within
> __apply_alternatives(), and are applied alongside patching for system
> capabilities as ARM64_NCAPS is not part of the boot_capabilities feature
> mask.
> 
> This special-casing is less than ideal. Giving special meaning to
> ARM64_NCAPS for this requires some structures and loops to use
> ARM64_NCAPS + 1 (AKA ARM64_NPATCHABLE), while others use ARM64_NCAPS.
> It's also not immediately clear callback alternatives are only applied
> when applying alternatives for system-wide features.
> 
> To make this a bit clearer, changes the way that callback alternatives
> are identified to remove the special-casing of ARM64_NCAPS, and to allow
> callback alternatives to be associated with a cpucap as with all other
> alternatives.
> 
> New cpucaps, ARM64_ALWAYS_BOOT and ARM64_ALWAYS_SYSTEM are added which
> are always detected alongside boot cpu capabilities and system
> capabilities respectively. All existing callback alternatives are made
> to use ARM64_ALWAYS_SYSTEM, and so will be patched at the same point
> during the boot flow as before.
> 
> Subsequent patches will make more use of these new cpucaps.
> 
> There should be no functional change as a result of this patch.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Joey Gouly <joey.gouly@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>   arch/arm64/include/asm/alternative-macros.h | 18 +++++++++-----
>   arch/arm64/include/asm/assembler.h          | 10 ++++----
>   arch/arm64/include/asm/cpufeature.h         |  4 +---
>   arch/arm64/include/asm/kvm_mmu.h            |  5 ++--
>   arch/arm64/kernel/alternative.c             | 26 +++++++++++----------
>   arch/arm64/kernel/cpufeature.c              | 19 +++++++++++++--
>   arch/arm64/kernel/entry.S                   |  8 +++----
>   arch/arm64/kvm/hyp/hyp-entry.S              |  4 ++--
>   arch/arm64/tools/cpucaps                    |  2 ++
>   9 files changed, 60 insertions(+), 36 deletions(-)
> 
> 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?

Thanks
Jon

-- 
nvpublic