Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[Barry Song]

On Tue, Mar 19, 2024 at 2:09 PM Barry Song <21cnbao@xxxxxxxxx> wrote:
>
> From: Barry Song <v-songbaohua@xxxxxxxx>
>
> xtensa's flush_dcache_page() can be a no-op sometimes. There is a
> generic implementation for this case in include/asm-generic/
> cacheflush.h.
>  #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
>  static inline void flush_dcache_page(struct page *page)
>  {
>  }
>
>  #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
>  #endif
>
> So remove the superfluous flush_dcache_page() definition, which also
> helps silence potential build warnings complaining the page variable
> passed to flush_dcache_page() is not used.
>
>    In file included from crypto/scompress.c:12:
>    include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone':
>    include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but not used [-Wunused-but-set-variable]
>       76 |                 struct page *page;
>          |                              ^~~~
>    crypto/scompress.c: In function 'scomp_acomp_comp_decomp':
> >> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wunused-variable]
>      174 |                         struct page *dst_page = sg_page(req->dst);
>          |
>
> The issue was originally reported on LoongArch by kernel test
> robot (Huacai fixed it on LoongArch), then reported by Guenter
> and me on xtensa.
>
> This patch also removes lots of redundant macros which have
> been defined by asm-generic/cacheflush.h.
>
> Cc: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp@xxxxxxxxx/
> Reported-by: Barry Song <v-songbaohua@xxxxxxxx>
> Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@xxxxxxxxxxxxxx/
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Hi Guenter,
I am not a xtensa guy, so I will need your help for a full test. if
turns out it is a too big(ambitious)
fix, a minimal fix might be:

diff --git a/arch/xtensa/include/asm/cacheflush.h
b/arch/xtensa/include/asm/cacheflush.h
index 38bcecb0e457..fdc692cf2b78 100644
--- a/arch/xtensa/include/asm/cacheflush.h
+++ b/arch/xtensa/include/asm/cacheflush.h
@@ -145,7 +145,7 @@ void local_flush_cache_page(struct vm_area_struct *vma,
 #define flush_cache_vunmap(start,end)                  do { } while (0)

 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
-#define flush_dcache_page(page)                                do { } while (0)
+#define flush_dcache_page(page)                                do {
(void)(page); } while (0)

 #define flush_icache_range local_flush_icache_range
 #define flush_cache_page(vma, addr, pfn)               do { } while (0)


> Closes: https://lore.kernel.org/all/aaa8b7d7-5abe-47bf-93f6-407942436472@xxxxxxxxxxxx/
> Fixes: 77292bb8ca69 ("crypto: scomp - remove memcpy if sg_nents is 1 and pages are lowmem")
> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
> ---
>  -v2: include asm-generic/cacheflush.h and remove lots of redundant macros
>
>  arch/xtensa/include/asm/cacheflush.h | 24 ++++++++----------------
>  1 file changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/arch/xtensa/include/asm/cacheflush.h b/arch/xtensa/include/asm/cacheflush.h
> index 38bcecb0e457..a2b6bb5429f5 100644
> --- a/arch/xtensa/include/asm/cacheflush.h
> +++ b/arch/xtensa/include/asm/cacheflush.h
> @@ -100,6 +100,10 @@ void flush_cache_range(struct vm_area_struct*, ulong, ulong);
>  void flush_icache_range(unsigned long start, unsigned long end);
>  void flush_cache_page(struct vm_area_struct*,
>                              unsigned long, unsigned long);
> +#define flush_cache_all flush_cache_all
> +#define flush_cache_range flush_cache_range
> +#define flush_icache_range flush_icache_range
> +#define flush_cache_page flush_cache_page
>  #else
>  #define flush_cache_all local_flush_cache_all
>  #define flush_cache_range local_flush_cache_range
> @@ -136,20 +140,7 @@ void local_flush_cache_page(struct vm_area_struct *vma,
>
>  #else
>
> -#define flush_cache_all()                              do { } while (0)
> -#define flush_cache_mm(mm)                             do { } while (0)
> -#define flush_cache_dup_mm(mm)                         do { } while (0)
> -
> -#define flush_cache_vmap(start,end)                    do { } while (0)
> -#define flush_cache_vmap_early(start,end)              do { } while (0)
> -#define flush_cache_vunmap(start,end)                  do { } while (0)
> -
> -#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
> -#define flush_dcache_page(page)                                do { } while (0)
> -
>  #define flush_icache_range local_flush_icache_range
> -#define flush_cache_page(vma, addr, pfn)               do { } while (0)
> -#define flush_cache_range(vma, start, end)             do { } while (0)
>
>  #endif
>
> @@ -162,15 +153,14 @@ void local_flush_cache_page(struct vm_area_struct *vma,
>                 __invalidate_icache_range(start,(end) - (start));       \
>         } while (0)
>
> -#define flush_dcache_mmap_lock(mapping)                        do { } while (0)
> -#define flush_dcache_mmap_unlock(mapping)              do { } while (0)
> -
>  #if defined(CONFIG_MMU) && (DCACHE_WAY_SIZE > PAGE_SIZE)
>
>  extern void copy_to_user_page(struct vm_area_struct*, struct page*,
>                 unsigned long, void*, const void*, unsigned long);
>  extern void copy_from_user_page(struct vm_area_struct*, struct page*,
>                 unsigned long, void*, const void*, unsigned long);
> +#define copy_to_user_page copy_to_user_page
> +#define copy_from_user_page copy_from_user_page
>
>  #else
>
> @@ -186,4 +176,6 @@ extern void copy_from_user_page(struct vm_area_struct*, struct page*,
>
>  #endif
>
> +#include <asm-generic/cacheflush.h>
> +
>  #endif /* _XTENSA_CACHEFLUSH_H */
> --
> 2.34.1
>

Thanks
Barry