Re: [PATCH v7] crypto: scompress: remove memcpy if sg_nents is 1 and pages are lowmem

[Guenter Roeck]

On 3/17/24 17:21, Barry Song wrote:
> On Mon, Mar 18, 2024 at 8:14 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > On 3/17/24 16:48, Barry Song wrote:
> > > On Mon, Mar 18, 2024 at 7:13 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > > > Hi,
> > > >
> > > > On Sat, Mar 02, 2024 at 08:27:45AM +1300, Barry Song wrote:
> > > > [ ... ]
> > > > > @@ -152,8 +165,17 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
> > > > >                         ret = -ENOSPC;
> > > > >                         goto out;
> > > > >                 }
> > > > > -             scatterwalk_map_and_copy(scratch->dst, req->dst, 0, req->dlen,
> > > > > -                                      1);
> > > > > +             if (dst == scratch->dst) {
> > > > > +                     scatterwalk_map_and_copy(scratch->dst, req->dst, 0,
> > > > > +                                              req->dlen, 1);
> > > > > +             } else {
> > > > > +                     int nr_pages = DIV_ROUND_UP(req->dst->offset + req->dlen, PAGE_SIZE);
> > > > > +                     int i;
> > > > > +                     struct page *dst_page = sg_page(req->dst);
> > > > > +
> > > > > +                     for (i = 0; i < nr_pages; i++)
> > > > > +                             flush_dcache_page(dst_page + i);
> > > >
> > > > flush_dcache_page() is an empty macro on some architectures
> > > > such as xtensa. This results in
> > >
> > > Hi Guenter,
> > >
> > > this is a bug of xtensa, could you test the patch:
> >
> > Thanks for the update.
> >
> > > https://lore.kernel.org/all/20240313045036.51065-1-21cnbao@xxxxxxxxx/
> >
> > That doesn't build for me.
> >
> >     CC      arch/xtensa/kernel/asm-offsets.s
> > In file included from ./include/linux/highmem.h:8,
> >                    from ./include/linux/bvec.h:10,
> >                    from ./include/linux/blk_types.h:10,
> >                    from ./include/linux/writeback.h:13,
> >                    from ./include/linux/memcontrol.h:23,
> >                    from ./include/linux/swap.h:9,
> >                    from ./include/linux/suspend.h:5,
> >                    from arch/xtensa/kernel/asm-offsets.c:24:
> > ./include/linux/cacheflush.h:9:5: error: "ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE" is not defined, evaluates to 0 [-Werror=undef]
> >       9 | #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
> >
> > A similar works for loongarch, so I don't know what is wrong.
> > Maybe some context patch is missing.
>
> this is weird as include/asm-generic/cacheflush.h will define it to 0
>
>   #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
>   static inline void flush_dcache_page(struct page *page)
>   {
>   }
>
>   #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
>   #endif
>
> Maybe somewhere else also needs to be fixed.
> Can you tell me your toolchain version and toolchain name? and defconfig name?

config is allmodconfig - GCC_PLUGINS.

Toolchains are self-built from gcc source using the buildall system. I tried
gcc 11.4, 12.3, and 13.2. I don't think that matters, though, since
"asm-generic/cacheflush.h" isn't included from arch/xtensa. The diff below
seems to fix the problem, but I have not fully tested it.

Guenter

---
diff --git a/arch/xtensa/include/asm/cacheflush.h b/arch/xtensa/include/asm/cacheflush.h
index 11efdc8eb262..62662919cbbc 100644
--- a/arch/xtensa/include/asm/cacheflush.h
+++ b/arch/xtensa/include/asm/cacheflush.h
@@ -183,4 +183,6 @@ extern void copy_from_user_page(struct vm_area_struct*, struct page*,

 #endif

+#include <asm-generic/cacheflush.h>
+
 #endif /* _XTENSA_CACHEFLUSH_H */