Re: [dpdk-dev] [PATCH v10 3/3] iFPGA: Add Intel FPGA BUS Rawdev Driver

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, May 09, 2018 at 04:33:45PM +0100, Zhang, Tianfei wrote:
> 
> 
> > -----Original Message-----
> > From: Thomas Monjalon [mailto:thomas@monjalon.net]
> > Sent: Wednesday, May 9, 2018 10:47 PM
> > To: Xu, Rosen <rosen.xu@intel.com>
> > Cc: dev@dpdk.org; Zhang, Roy Fan <roy.fan.zhang@intel.com>; Doherty,
> > Declan <declan.doherty@intel.com>; Richardson, Bruce
> > <bruce.richardson@intel.com>; shreyansh.jain@nxp.com; Yigit, Ferruh
> > <ferruh.yigit@intel.com>; Ananyev, Konstantin
> > <konstantin.ananyev@intel.com>; Zhang, Tianfei <tianfei.zhang@intel.com>;
> > Liu, Song <song.liu@intel.com>; Wu, Hao <hao.wu@intel.com>;
> > gaetan.rivet@6wind.com; Wu, Yanglong <yanglong.wu@intel.com>
> > Subject: Re: [dpdk-dev] [PATCH v10 3/3] iFPGA: Add Intel FPGA BUS Rawdev
> > Driver
> > 
> > 09/05/2018 09:43, Xu, Rosen:
> > > From: Rosen Xu <rosen.xu@intel.com>
> > >
> > > Add Intel FPGA BUS Rawdev Driver which is based on librte_rawdev
> > > library.
> > >
> > > Signed-off-by: Rosen Xu <rosen.xu@intel.com>
> > > Signed-off-by: Yanglong Wu <yanglong.wu@intel.com>
> > > Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
> > > Acked-by: Shreyansh Jain <shreyansh.jain@nxp.com>
> > 
> > I have a compilation error:
> > 	drivers/raw/ifpga_rawdev/base/ifpga_fme_pr.c:10:15: error:
> > 	instruction requires: AVX-512 ISA
> > 
> > because of vmovdqu64:
> > 
> > #if defined(RTE_ARCH_X86_64)
> > static inline void copy512(const void *src, void *dst) {
> >     asm volatile("vmovdqu64 (%0), %%zmm0;"
> >              "vmovntdq %%zmm0, (%1);"
> >              :
> >              : "r"(src), "r"(dst));
> > }
> > #else
> > static inline void copy512(const void *src, void *dst) {
> >     UNUSED(src);
> >     UNUSED(dst);
> >     WARN_ON(1);
> > }
> > #endif
> > 
> > I suggest to fix it quickly without waiting a v11 with this:
> > 
> > static inline void copy512(const void *src, void *dst) { #ifdef
> > CC_SUPPORT_AVX512F
> >     asm volatile("vmovdqu64 (%0), %%zmm0;"
> >              "vmovntdq %%zmm0, (%1);"
> >              :
> >              : "r"(src), "r"(dst));
> > #else
> >     UNUSED(src);
> >     UNUSED(dst);
> >     WARN_ON(1);
> > #endif
> > }
> > 
> > It does not make any runtime detection, but it's better than previously.
> > 
> 
> Which linux distribution are you use? We can compile it on Ubuntu 16.04 and RHEL 7.4.
> We will fix it on V11.
> 

This shows up with meson builds for non-avx-512 architectures using clang.
The makefile has the following snippet that doesn't have an equivalent in
the meson.build file.

 26 ifeq ($(CONFIG_RTE_TOOLCHAIN_CLANG),y)$
 27 >-------CFLAGS_ifpga_fme_pr.o += -march=knl$
 28 endif$

However, it does also bring up the questions as to the unconditional use of
AVX-512 code? What happens if this code is run on a system without AVX-512
support?

Regards,
/Bruce