linux-kernel - Re: [PATCH v3 1/2] Introduce cpu_icache_is

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Message-ID: <a3fd2a24-16ff-4fa5-9510-148f66c19ca9@efficios.com>
Date: Sat, 7 Dec 2024 12:01:52 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Zi Yan <ziy@...dia.com>, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Vlastimil Babka <vbabka@...e.cz>, David Hildenbrand <david@...hat.com>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 Miaohe Lin <linmiaohe@...wei.com>, Kefeng Wang <wangkefeng.wang@...wei.com>,
 John Hubbard <jhubbard@...dia.com>,
 "Huang, Ying" <ying.huang@...ux.alibaba.com>,
 Ryan Roberts <ryan.roberts@....com>, Alexander Potapenko
 <glider@...gle.com>, Kees Cook <keescook@...omium.org>,
 Vineet Gupta <vgupta@...nel.org>, linux-kernel@...r.kernel.org,
 linux-snps-arc@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] Introduce cpu_icache_is_aliasing() across all
 architectures

On 2024-12-07 11:55, Zi Yan wrote:
> In commit eacd0e950dc2 ("ARC: [mm] Lazy D-cache flush (non aliasing
> VIPT)"), arc adds the need to flush dcache to make icache see the code
> page change. This also requires special handling for
> clear_user_(high)page(). Introduce cpu_icache_is_aliasing() to make
> MM code query special clear_user_(high)page() easier. This will be used
> by the following commit.
> 
> Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Signed-off-by: Zi Yan <ziy@...dia.com>

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

> ---
>   arch/arc/Kconfig                 | 1 +
>   arch/arc/include/asm/cachetype.h | 8 ++++++++
>   include/linux/cacheinfo.h        | 6 ++++++
>   3 files changed, 15 insertions(+)
>   create mode 100644 arch/arc/include/asm/cachetype.h
> 
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 5b2488142041..e96935373796 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -6,6 +6,7 @@
>   config ARC
>   	def_bool y
>   	select ARC_TIMERS
> +	select ARCH_HAS_CPU_CACHE_ALIASING
>   	select ARCH_HAS_CACHE_LINE_SIZE
>   	select ARCH_HAS_DEBUG_VM_PGTABLE
>   	select ARCH_HAS_DMA_PREP_COHERENT
> diff --git a/arch/arc/include/asm/cachetype.h b/arch/arc/include/asm/cachetype.h
> new file mode 100644
> index 000000000000..acd3b6cb4bf5
> --- /dev/null
> +++ b/arch/arc/include/asm/cachetype.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __ASM_ARC_CACHETYPE_H
> +#define __ASM_ARC_CACHETYPE_H
> +
> +#define cpu_dcache_is_aliasing()	false
> +#define cpu_icache_is_aliasing()	true
> +
> +#endif
> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
> index 108060612bb8..7ad736538649 100644
> --- a/include/linux/cacheinfo.h
> +++ b/include/linux/cacheinfo.h
> @@ -155,8 +155,14 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
>   
>   #ifndef CONFIG_ARCH_HAS_CPU_CACHE_ALIASING
>   #define cpu_dcache_is_aliasing()	false
> +#define cpu_icache_is_aliasing()	cpu_dcache_is_aliasing()
>   #else
>   #include <asm/cachetype.h>
> +
> +#ifndef cpu_icache_is_aliasing
> +#define cpu_icache_is_aliasing()	cpu_dcache_is_aliasing()
> +#endif
> +
>   #endif
>   
>   #endif /* _LINUX_CACHEINFO_H */

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com