Re: [dpdk-dev] [PATCH v2] eal/cpuflags: add x86 based cpu flags

[Neil Horman <nhorman@tuxdriver.com>]

On Fri, Mar 27, 2020 at 01:24:12PM +0100, David Marchand wrote:
> On Wed, Mar 25, 2020 at 12:11 PM Kevin Laatz <kevin.laatz@intel.com> wrote:
> >
> > This patch adds CPU flags which will enable the detection of ISA
> > features available on more recent x86 based CPUs.
> >
> > The CPUID leaf information can be found in Section 1.7 of this
> > document:
> > https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf
> >
> > The following CPU flags are added in this patch:
> >     - AVX-512 doubleword and quadword instructions.
> >     - AVX-512 integer fused multiply-add instructions.
> >     - AVX-512 conflict detection instructions.
> >     - AVX-512 byte and word instructions.
> >     - AVX-512 vector length instructions.
> >     - AVX-512 vector bit manipulation instructions.
> >     - AVX-512 vector bit manipulation 2 instructions.
> >     - Galois field new instructions.
> >     - Vector AES instructions.
> >     - Vector carry-less multiply instructions.
> >     - AVX-512 vector neural network instructions.
> >     - AVX-512 for bit algorithm instructions.
> >     - AVX-512 vector popcount instructions.
> >     - Cache line demote instructions.
> >     - Direct store instructions.
> >     - Direct store 64B instructions.
> >     - AVX-512 two register intersection instructions.
> >
> > Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
> > ---
> >  lib/librte_eal/common/arch/x86/rte_cpuflags.c  | 18 ++++++++++++++++++
> >  .../common/include/arch/x86/rte_cpuflags.h     | 18 ++++++++++++++++++
> >  2 files changed, 36 insertions(+)
> >
> > diff --git a/lib/librte_eal/common/arch/x86/rte_cpuflags.c b/lib/librte_eal/common/arch/x86/rte_cpuflags.c
> > index 6492df556..30439e795 100644
> > --- a/lib/librte_eal/common/arch/x86/rte_cpuflags.c
> > +++ b/lib/librte_eal/common/arch/x86/rte_cpuflags.c
> > @@ -120,6 +120,24 @@ const struct feature_entry rte_cpu_feature_table[] = {
> >         FEAT_DEF(EM64T, 0x80000001, 0, RTE_REG_EDX, 29)
> >
> >         FEAT_DEF(INVTSC, 0x80000007, 0, RTE_REG_EDX,  8)
> > +
> > +       FEAT_DEF(AVX512DQ, 0x00000007, 0, RTE_REG_EBX, 17)
> > +       FEAT_DEF(AVX512IFMA, 0x00000007, 0, RTE_REG_EBX, 21)
> > +       FEAT_DEF(AVX512CD, 0x00000007, 0, RTE_REG_EBX, 28)
> > +       FEAT_DEF(AVX512BW, 0x00000007, 0, RTE_REG_EBX, 30)
> > +       FEAT_DEF(AVX512VL, 0x00000007, 0, RTE_REG_EBX, 31)
> > +       FEAT_DEF(AVX512VBMI, 0x00000007, 0, RTE_REG_ECX, 1)
> > +       FEAT_DEF(AVX512VBMI2, 0x00000007, 0, RTE_REG_ECX, 6)
> > +       FEAT_DEF(GFNI, 0x00000007, 0, RTE_REG_ECX, 8)
> > +       FEAT_DEF(VAES, 0x00000007, 0, RTE_REG_ECX, 9)
> > +       FEAT_DEF(VPCLMULQDQ, 0x00000007, 0, RTE_REG_ECX, 10)
> > +       FEAT_DEF(AVX512VNNI, 0x00000007, 0, RTE_REG_ECX, 11)
> > +       FEAT_DEF(AVX512BITALG, 0x00000007, 0, RTE_REG_ECX, 12)
> > +       FEAT_DEF(AVX512VPOPCNTDQ, 0x00000007, 0, RTE_REG_ECX,  14)
> > +       FEAT_DEF(CLDEMOTE, 0x00000007, 0, RTE_REG_ECX, 25)
> > +       FEAT_DEF(MOVDIRI, 0x00000007, 0, RTE_REG_ECX, 27)
> > +       FEAT_DEF(MOVDIR64B, 0x00000007, 0, RTE_REG_ECX, 28)
> > +       FEAT_DEF(AVX512VP2INTERSECT, 0x00000007, 0, RTE_REG_EDX, 8)
> >  };
> >
> >  int
> > diff --git a/lib/librte_eal/common/include/arch/x86/rte_cpuflags.h b/lib/librte_eal/common/include/arch/x86/rte_cpuflags.h
> > index 25ba47b96..f8f73b19f 100644
> > --- a/lib/librte_eal/common/include/arch/x86/rte_cpuflags.h
> > +++ b/lib/librte_eal/common/include/arch/x86/rte_cpuflags.h
> > @@ -113,6 +113,24 @@ enum rte_cpu_flag_t {
> >         /* (EAX 80000007h) EDX features */
> >         RTE_CPUFLAG_INVTSC,                 /**< INVTSC */
> >
> > +       RTE_CPUFLAG_AVX512DQ,               /**< AVX512 Doubleword and Quadword */
> > +       RTE_CPUFLAG_AVX512IFMA,             /**< AVX512 Integer Fused Multiply-Add */
> > +       RTE_CPUFLAG_AVX512CD,               /**< AVX512 Conflict Detection*/
> > +       RTE_CPUFLAG_AVX512BW,               /**< AVX512 Byte and Word */
> > +       RTE_CPUFLAG_AVX512VL,               /**< AVX512 Vector Length */
> > +       RTE_CPUFLAG_AVX512VBMI,             /**< AVX512 Vector Bit Manipulation */
> > +       RTE_CPUFLAG_AVX512VBMI2,            /**< AVX512 Vector Bit Manipulation 2 */
> > +       RTE_CPUFLAG_GFNI,                   /**< Galois Field New Instructions */
> > +       RTE_CPUFLAG_VAES,                   /**< Vector AES */
> > +       RTE_CPUFLAG_VPCLMULQDQ,             /**< Vector Carry-less Multiply */
> > +       RTE_CPUFLAG_AVX512VNNI,             /**< AVX512 Vector Neural Network Instructions */
> > +       RTE_CPUFLAG_AVX512BITALG,           /**< AVX512 Bit Algorithms */
> > +       RTE_CPUFLAG_AVX512VPOPCNTDQ,        /**< AVX512 Vector Popcount */
> > +       RTE_CPUFLAG_CLDEMOTE,               /**< Cache Line Demote */
> > +       RTE_CPUFLAG_MOVDIRI,                /**< Direct Store Instructions */
> > +       RTE_CPUFLAG_MOVDIR64B,              /**< Direct Store Instructions 64B */
> > +       RTE_CPUFLAG_AVX512VP2INTERSECT,     /**< AVX512 Two Register Intersection */
> > +
> >         /* The last item */
> >         RTE_CPUFLAG_NUMFLAGS,               /**< This should always be the last! */
> 
> This is seen as an ABI break because of the change on _NUMFLAGS:
> https://travis-ci.com/github/ovsrobot/dpdk/jobs/302524264#L2351
> 
It shouldn't be, as the only API calls we expose that use rte_cpu_flag_t accept
it as an integer parameter to see if the flag is enabled.  Theres no use of the
enum in a public array or any struct that is sized based on the number of flags,
so you should be good to go
Neil

> 
> -- 
> David Marchand
> 
>