[v2,2/2] build: fix crash by disabling AVX512 with binutils 2.31

  On Skylake platform, with native build, KNI kernel module crashes
because of the corrupted values passed to kernel module.

The corruption occurs because the userspace kni library works
unexpectedly. Compiler [1] is using AVX512 instructions and generated
binary is wrong [2].

It turned around gcc does its job correct, but gas is generating binary
wrong. And expected binutils 2.30, 2.31 & 2.31.1 are affected. Issue has
been fixed in binutils 2.32 with:
Commit x86: don't mistakenly scale non-8-bit displacements

AVX512 was already disabled with bintuils 2.30 [3], extending it to
2.31 & 2.31.1 too.

[1] gcc (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2)

[2] gcc bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90028

[3] Bugzilla ID 97 has the details.

Bugzilla ID: 249
Cc: stable@dpdk.org

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
---
v2:
* Release notes "Known Issues" section updated
---
 config/x86/meson.build                   | 6 ++++++
 doc/guides/rel_notes/release_19_05.rst   | 6 ++++++
 mk/toolchain/gcc/rte.toolchain-compat.mk | 9 ++++++++-
 3 files changed, 20 insertions(+), 1 deletion(-)
  

On Tue, Apr 16, 2019 at 04:39:32PM +0100, Ferruh Yigit wrote:
> On Skylake platform, with native build, KNI kernel module crashes
> because of the corrupted values passed to kernel module.
> 
> The corruption occurs because the userspace kni library works
> unexpectedly. Compiler [1] is using AVX512 instructions and generated
> binary is wrong [2].
> 
> It turned around gcc does its job correct, but gas is generating binary
> wrong. And expected binutils 2.30, 2.31 & 2.31.1 are affected. Issue has
> been fixed in binutils 2.32 with:
> Commit x86: don't mistakenly scale non-8-bit displacements
> 
> AVX512 was already disabled with bintuils 2.30 [3], extending it to
> 2.31 & 2.31.1 too.
> 
> [1] gcc (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2)
> 
> [2] gcc bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90028
> 
> [3] Bugzilla ID 97 has the details.
> 
> Bugzilla ID: 249
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
> v2:
> * Release notes "Known Issues" section updated
> ---
>  config/x86/meson.build                   | 6 ++++++
>  doc/guides/rel_notes/release_19_05.rst   | 6 ++++++
>  mk/toolchain/gcc/rte.toolchain-compat.mk | 9 ++++++++-
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/config/x86/meson.build b/config/x86/meson.build
> index 692aebe7a..9e9d5dc8c 100644
> --- a/config/x86/meson.build
> +++ b/config/x86/meson.build
> @@ -10,6 +10,12 @@ if host_machine.system() != 'windows'
>  			message('Binutils 2.30 detected, disabling AVX512 support as workaround for bug #97')
>  		endif
>  	endif
> +	if ldver.contains('2.31')
> +		if cc.has_argument('-mno-avx512f')
> +			machine_args += '-mno-avx512f'
> +			message('Binutils 2.31 detected, disabling AVX512 support as workaround for bug #249')
> +		endif
> +	endif

Is this not the same as the previous block just with a slightly different
error message? Should we merge the two, and print out both bug numbers?

If not merging, we can reduce the indentation by putting the second
cc.has_argument() condition on the same line as the previous check, i.e.
	"if ldver.contains(...) and cc.has_argument(...)"

Apart from this nit:

Acked-by: Bruce Richardson <bruce.richardson@intel.com>