On Wed, Nov 17, 2021 at 10:55 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Wed, Nov 17, 2021 at 10:46 AM kernel test robot <lkp@intel.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/core
> > head:   d31c3c683ee668ba5d87c0730610442fd672525f
> > commit: d31c3c683ee668ba5d87c0730610442fd672525f [1/1] x86/csum: Rewrite/optimize csum_partial()
> > config: um-x86_64_defconfig (attached as .config)
> > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> > reproduce (this is a W=1 build):
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=d31c3c683ee668ba5d87c0730610442fd672525f
> >         git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
> >         git fetch --no-tags tip x86/core
> >         git checkout d31c3c683ee668ba5d87c0730610442fd672525f
> >         # save the attached .config to linux build tree
> >         make W=1 ARCH=um SUBARCH=x86_64
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All errors (new ones prefixed by >>):
> >
> >    arch/x86/um/../lib/csum-partial_64.c: In function 'csum_partial':
> > >> arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad' [-Werror=implicit-function-declaration]
> >       98 |   trail = (load_unaligned_zeropad(buff) << shift) >> shift;
> >          |            ^~~~~~~~~~~~~~~~~~~~~~
> >    cc1: some warnings being treated as errors
> >
> >
>
> Hmmm... it seems we need to guard this with CONFIG_DCACHE_WORD_ACCESS ?

Perhaps something like the following ?

diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index 5ec35626945b6db2f7f41c6d46d5e422810eac46..d419b9345d6dba2e924887671bc6f11c3e17ebd7
100644
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -91,12 +91,23 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
                        : "memory");
                buff += 8;
        }
-       if (len & 7) {
-               unsigned int shift = (8 - (len & 7)) * 8;
+       len &= 7;
+       if (len) {
                unsigned long trail;
+#ifndef CONFIG_DCACHE_WORD_ACCESS
+               union {
+                       unsigned long   ulval;
+                       u8              bytes[sizeof(long)];
+               } v;

-               trail = (load_unaligned_zeropad(buff) << shift) >> shift;
+               v.ulval = 0;
+               memcpy(v.bytes, buff, len);
+               trail = v.ulval;
+#else
+               unsigned int shift = (sizeof(long) - len) * BITS_PER_BYTE;

+               trail = (load_unaligned_zeropad(buff) << shift) >> shift;
+#endif
                asm("addq %[trail],%[res]\n\t"
                    "adcq $0,%[res]"
                        : [res] "+r" (temp64)