On Thu, Sep 07, 2017 at 10:31:17AM +0100, Li, Xiaoyun wrote:
> Hi
> So I should delete the mk/machine/atm folder and add a new
> mk/machine/silvermont folder, right?
> And in silvermont/rte.vars.mk, there is sentence " MACHINE_CFLAGS =
> -march=silvermont ".
> The annotation just adds the copy of others like original atm?
> Another thing, we don't need to create the config file
> (defconfig_x86_64-silvermont-linuxapp-gcc), right?
>
Yes, that is correct.
> Best Regards
> Xiaoyun Li
>
Thanks,
/Bruce
>
>
> -----Original Message-----
> From: Richardson, Bruce
> Sent: Thursday, September 7, 2017 16:57
> To: Li, Xiaoyun <xiaoyun...@intel.com>
> Cc: dev@dpdk.org; Zhang, Helin <helin.zh...@intel.com>; sta...@dpdk.org
> Subject: Re: [PATCH] mk: fix compiling error for atom target
>
> On Thu, Sep 07, 2017 at 04:35:17PM +0800, Xiaoyun Li wrote:
> > GCC thinks target atom doesn't support SSE4.2 and SSE4 is now part of
> > minimum requirements for DPDK on x86. So there are compiling errors
> > when cross-compiling for target atom. And in fact, the atom supports SSE4
> > now.
> > This patch fixes this issue.
> >
> > Fixes: 5ea4d4688dce ("net/ixgbe: remove fallback code for x86
> > non-SSE4")
> > Cc: sta...@dpdk.org
> >
> > Signed-off-by: Xiaoyun Li <xiaoyun...@intel.com>
>
> The -march=atom flag is for older atom CPUs, and is no longer advertised by
> gcc, since all -march flags now correspond to the actual core
> microarchitecture used. [man gcc on Fedora 26, no longer lists atom as a
> valid march value, though it's probably still accepted for backward
> compatibility]. The direct replacement for atom is "bonnell", which does not
> have SSE4.2 support, so we should not use. What we do support is later atoms,
> so the architecture targets for atom should be "-march=silvermont". This
> automatically includes sse4 support so no additional flags needed.
>
> Note: I previously had this discussion with Neil on-list, but forgot to do
> the follow-up work agreed on. See:
> https://www.mail-archive.com/dev@dpdk.org/msg72629.html
> The agreed plan was to remove atom as a target for DPDK builds and add a
> "silvermont" replacement instead. If you have time, perhaps you could look at
> doing that instead of this fix?
>
> /Bruce
>
> > ---
> > mk/machine/atm/rte.vars.mk | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/mk/machine/atm/rte.vars.mk b/mk/machine/atm/rte.vars.mk
> > index cfed110..a6899d9 100644
> > --- a/mk/machine/atm/rte.vars.mk
> > +++ b/mk/machine/atm/rte.vars.mk
> > @@ -56,3 +56,5 @@
> > # CPU_ASFLAGS =
> >
> > MACHINE_CFLAGS = -march=atom
> > +
> > +MACHINE_CFLAGS += -msse4.2
> > --
> > 2.7.4
> >
