Messages in this thread | | | From | Barry Song <> | Date | Mon, 29 Apr 2024 21:11:45 +1200 | Subject | Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros |
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On Mon, Apr 29, 2024 at 5:10 PM Max Filippov <jcmvbkbc@gmail.com> wrote: > > On Sat, Apr 27, 2024 at 12:05 PM Guenter Roeck <linux@roeck-us.net> wrote: > > > > Hi, > > > > On Tue, Mar 19, 2024 at 02:09:20PM +1300, Barry Song wrote: > > > From: Barry Song <v-songbaohua@oppo.com> > > > > > > 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@loongson.cn> > > > Cc: Herbert Xu <herbert@gondor.apana.org.au> > > > Reported-by: kernel test robot <lkp@intel.com> > > > Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp@intel.com/ > > > Reported-by: Barry Song <v-songbaohua@oppo.com> > > > Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@mail.gmail.com/ > > > Reported-by: Guenter Roeck <linux@roeck-us.net> > > > Closes: https://lore.kernel.org/all/aaa8b7d7-5abe-47bf-93f6-407942436472@roeck-us.net/ > > > Fixes: 77292bb8ca69 ("crypto: scomp - remove memcpy if sg_nents is 1 and pages are lowmem") > > > Signed-off-by: Barry Song <v-songbaohua@oppo.com> > > > > The mainline kernel still fails to build xtensa:allmodconfig. > > > > Building xtensa:allmodconfig ... failed > > -------------- > > Error log: > > crypto/scompress.c: In function 'scomp_acomp_comp_decomp': > > crypto/scompress.c:174:38: error: unused variable 'dst_page' [-Werror=unused-variable] > > 174 | struct page *dst_page = sg_page(req->dst); > > > > This patch fixes the problem. Is there a chance to get it applied to the > > upstream kernel, or should I just stop build testing xtensa:allmodconfig ? > > Applied to my xtensa tree.
Thanks for taking care of this, Max!
> I was still hoping to see rationale for why this is a useful warning.
Personally, I think the reason is quite obvious.
This warning serves as a valuable alert, highlighting an issue where Xtensa fails to properly implement flush_dcache_page(). The problem lies in a macro definition that neglects to evaluate its argument. Such discrepancies can impact driver functionality across various architectures, rendering them independent of specific architectural considerations.
> > -- > Thanks. > -- Max
Thanks Barry
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