linux-kernel - Re: [PATCH] um: fix and optimize xor select template for CONFIG64 and timetravel mode

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Date:   Wed, 12 Jan 2022 10:03:28 +0000
From:   Anton Ivanov <anton.ivanov@...bridgegreys.com>
To:     Benjamin Beichler <benjamin.beichler@...-rostock.de>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>
Cc:     johannes.berg@...el.com, linux-um@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: fix and optimize xor select template for CONFIG64 and
 timetravel mode



On 11/01/2022 20:05, Benjamin Beichler wrote:
> Due to dropped inclusion of asm-generic/xor.h, xor_block_8regs symbol is
> missing with CONFIG64 and break compilation, as the asm/xor_64.h also did
> not include it. The patch recreate the logic from arch/x86, which check
> whether AVX is available and add fallbacks for 32bit and 64bit config of
> um.
> 
> A very minor additional "fix" is, the return of the macro parameter
> instead of NULL, as this is the original intent of the macro, but
> this does not change the actual behavior.
> 
> Fixes: c0ecca6604b8 ("um: enable the use of optimized xor routines in UML")
> Signed-off-by: Benjamin Beichler <benjamin.beichler@...-rostock.de>
> ---
>   arch/um/include/asm/xor.h | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/um/include/asm/xor.h b/arch/um/include/asm/xor.h
> index f512704a9ec7..22b39de73c24 100644
> --- a/arch/um/include/asm/xor.h
> +++ b/arch/um/include/asm/xor.h
> @@ -4,8 +4,10 @@
>   
>   #ifdef CONFIG_64BIT
>   #undef CONFIG_X86_32
> +#define TT_CPU_INF_XOR_DEFAULT (AVX_SELECT(&xor_block_sse_pf64))
>   #else
>   #define CONFIG_X86_32 1
> +#define TT_CPU_INF_XOR_DEFAULT (AVX_SELECT(&xor_block_8regs))
>   #endif
>   
>   #include <asm/cpufeature.h>
> @@ -16,7 +18,7 @@
>   #undef XOR_SELECT_TEMPLATE
>   /* pick an arbitrary one - measuring isn't possible with inf-cpu */
>   #define XOR_SELECT_TEMPLATE(x)	\
> -	(time_travel_mode == TT_MODE_INFCPU ? &xor_block_8regs : NULL)
> +	(time_travel_mode == TT_MODE_INFCPU ? TT_CPU_INF_XOR_DEFAULT : x))
>   #endif
>   
>   #endif
> 
Acked-By: Anton Ivanov <anton.ivanov@...bridgegreys.com>
-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/