On Tue, Mar 27, 2018 at 05:22:32PM +0200, LEROY Christophe wrote: > Shile Zhang <shile.zh...@nokia.com> a écrit : > > >fix the missed point in Paul's patch: > >"powerpc/64: Fix checksum folding in csum_tcpudp_nofold and > >ip_fast_csum_nofold" > > > >Signed-off-by: Shile Zhang <shile.zh...@nokia.com> > >--- > > arch/powerpc/include/asm/checksum.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > >diff --git a/arch/powerpc/include/asm/checksum.h > >b/arch/powerpc/include/asm/checksum.h > >index 5b1a6e3..430d038 100644 > >--- a/arch/powerpc/include/asm/checksum.h > >+++ b/arch/powerpc/include/asm/checksum.h > >@@ -108,7 +108,7 @@ static inline __wsum csum_add(__wsum csum, __wsum addend) > > > > #ifdef __powerpc64__ > > res += (__force u64)addend; > >- return (__force __wsum)((u32)res + (res >> 32)); > >+ return (__force __wsum) from64to32(res); > > Did you encounter a bug due to that ? > As far as i understand, csum and addend are 32 bits so can't exceed 0xffffffff > Then their sum won't exceed 0x1fffffffe. So the sum of upper and lower part > won't carry
If the sum of the two halves was 0x1fffffffe, then that previously got truncated to 32 bits and returned as 0xfffffffe, which is wrong - the result should be 0xffffffff. Paul.
