* [PATCH V3] mm: page-flags-layout.h: change the KASAN_TAG_WIDTH for HW_TAGS
@ 2025-04-28 20:14 Guilherme Giacomo Simoes
2025-05-04 21:34 ` Andrey Konovalov
0 siblings, 1 reply; 2+ messages in thread
From: Guilherme Giacomo Simoes @ 2025-04-28 20:14 UTC (permalink / raw)
To: akpm, pasha.tatashin, surenb
Cc: linux-mm, linux-kernel, Guilherme Giacomo Simoes, Andrey Konovalov
the KASAN_TAG_WIDTH is 8 bits for both (HW_TAGS and SW_TAGS), but for
HW_TAGS the KASAN_TAG_WIDTH can be 4 bits bits because due to the design
of the MTE the memory words for storing metadata only need 4 bits.
Change the preprocessor define KASAN_TAG_WIDTH for check if SW_TAGS is
define, so KASAN_TAG_WIDTH should be 8 bits, but if HW_TAGS is define,
so KASAN_TAG_WIDTH should be 4 bits to save a few flags bits.
Suggested-by: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Guilherme Giacomo Simoes <trintaeoitogc@gmail.com>
---
V3 changes
- improve commit title
---
include/linux/page-flags-layout.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
index 4f5c9e979bb9..760006b1c480 100644
--- a/include/linux/page-flags-layout.h
+++ b/include/linux/page-flags-layout.h
@@ -72,8 +72,10 @@
#define NODE_NOT_IN_PAGE_FLAGS 1
#endif
-#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
+#if defined(CONFIG_KASAN_SW_TAGS)
#define KASAN_TAG_WIDTH 8
+#elif defined(CONFIG_KASAN_HW_TAGS)
+#define KASAN_TAG_WIDTH 4
#else
#define KASAN_TAG_WIDTH 0
#endif
--
2.34.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH V3] mm: page-flags-layout.h: change the KASAN_TAG_WIDTH for HW_TAGS
2025-04-28 20:14 [PATCH V3] mm: page-flags-layout.h: change the KASAN_TAG_WIDTH for HW_TAGS Guilherme Giacomo Simoes
@ 2025-05-04 21:34 ` Andrey Konovalov
0 siblings, 0 replies; 2+ messages in thread
From: Andrey Konovalov @ 2025-05-04 21:34 UTC (permalink / raw)
To: Guilherme Giacomo Simoes
Cc: akpm, pasha.tatashin, surenb, linux-mm, linux-kernel
On Mon, Apr 28, 2025 at 10:14 PM Guilherme Giacomo Simoes
<trintaeoitogc@gmail.com> wrote:
>
> the KASAN_TAG_WIDTH is 8 bits for both (HW_TAGS and SW_TAGS), but for
> HW_TAGS the KASAN_TAG_WIDTH can be 4 bits bits because due to the design
> of the MTE the memory words for storing metadata only need 4 bits.
> Change the preprocessor define KASAN_TAG_WIDTH for check if SW_TAGS is
> define, so KASAN_TAG_WIDTH should be 8 bits, but if HW_TAGS is define,
> so KASAN_TAG_WIDTH should be 4 bits to save a few flags bits.
>
> Suggested-by: Andrey Konovalov <andreyknvl@gmail.com>
> Signed-off-by: Guilherme Giacomo Simoes <trintaeoitogc@gmail.com>
> ---
> V3 changes
> - improve commit title
> ---
> include/linux/page-flags-layout.h | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
> index 4f5c9e979bb9..760006b1c480 100644
> --- a/include/linux/page-flags-layout.h
> +++ b/include/linux/page-flags-layout.h
> @@ -72,8 +72,10 @@
> #define NODE_NOT_IN_PAGE_FLAGS 1
> #endif
>
> -#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> +#if defined(CONFIG_KASAN_SW_TAGS)
> #define KASAN_TAG_WIDTH 8
> +#elif defined(CONFIG_KASAN_HW_TAGS)
> +#define KASAN_TAG_WIDTH 4
> #else
> #define KASAN_TAG_WIDTH 0
> #endif
> --
> 2.34.1
>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
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2025-04-28 20:14 [PATCH V3] mm: page-flags-layout.h: change the KASAN_TAG_WIDTH for HW_TAGS Guilherme Giacomo Simoes
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