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From: Ray Kinsella <mdr@ashroe.eu>
To: "Van Haaren, Harry" <harry.van.haaren@intel.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	Neil Horman <nhorman@tuxdriver.com>,
	Dodji Seketeli <dodji@redhat.com>
Cc: David Marchand <david.marchand@redhat.com>,
	"Laatz, Kevin" <kevin.laatz@intel.com>, dev <dev@dpdk.org>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2] eal/cpuflags: add x86 based cpu flags
Date: Fri, 27 Mar 2020 14:36:51 +0000
Message-ID: <cba0017a-7c5b-e357-a7b9-59c6334efee6@ashroe.eu> (raw)
In-Reply-To: <BYAPR11MB3143EF670B2F9FDA4A738BEDD7CC0@BYAPR11MB3143.namprd11.prod.outlook.com>



On 27/03/2020 14:32, Van Haaren, Harry wrote:
>> -----Original Message-----
>> From: Thomas Monjalon <thomas@monjalon.net>
>> Sent: Friday, March 27, 2020 2:16 PM
>> To: Neil Horman <nhorman@tuxdriver.com>; Dodji Seketeli <dodji@redhat.com>;
>> mdr@ashroe.eu
>> Cc: David Marchand <david.marchand@redhat.com>; Laatz, Kevin
>> <kevin.laatz@intel.com>; dev <dev@dpdk.org>; Richardson, Bruce
>> <bruce.richardson@intel.com>; Van Haaren, Harry <harry.van.haaren@intel.com>;
>> Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
>> Subject: Re: [dpdk-dev] [PATCH v2] eal/cpuflags: add x86 based cpu flags
>>
>> 27/03/2020 14:44, Neil Horman:
>>> 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:
>>>>> --- 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
>>
>> Indeed I cannot imagine an ABI incompatibility in this case.
>> The only behaviour change is to accept new (higher) RTE_CPUFLAG values
>> in functions rte_cpu_get_flag_enabled() and rte_cpu_get_flag_name().
>> Is changing the range of valid values an ABI break?
>> Why is it flagged by libabigail?
> 
> If this enum _MAX value was used by the application to allocate an array, that later our DPDK code would write to it could cause out-of-bounds array accesses of the application supplied array. Abigail doesn't know what applications could use the value for, so it flags it.
> 
> IMO Abigail is right to flag it to us - a manual review to understand what that _MAX enum value is used for, and then decide on a case by case basis seems the best way forward to me.
> 
> Thanks Neil/Thomas for reviewing, as reply in this thread, I also believe this is not going to break ABI.
> 
 
+1 to Harrry's comments. 
I can't immediately see how this might break the ABI either. 

  reply index

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 11:49 [dpdk-dev] [PATCH 00/17] Add CPU flags Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 01/17] eal/cpuflags: add avx512 doubleword and quadword Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 02/17] eal/cpuflags: add avx512 integer fused multiply-add Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 03/17] eal/cpuflags: add avx512 conflict detection Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 04/17] eal/cpuflags: add avx512 byte and word Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 05/17] eal/cpuflags: add avx512 vector length Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 06/17] eal/cpuflags: add avx512 vector bit manipulation Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 07/17] eal/cpuflags: add avx512 vector bit manipulation 2 Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 08/17] eal/cpuflags: add galois field new instructions Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 09/17] eal/cpuflags: add vector AES Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 10/17] eal/cpuflags: add vector carry-less multiply Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 11/17] eal/cpuflags: add avx512 vector neural network instructions Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 12/17] eal/cpuflags: add avx512 bit algorithms Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 13/17] eal/cpuflags: add avx512 vector popcount Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 14/17] eal/cpuflags: add cache line demote Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 15/17] eal/cpuflags: add direct store instructions Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 16/17] eal/cpuflags: add direct store instructions 64B Kevin Laatz
2020-03-24 11:49 ` [dpdk-dev] [PATCH 17/17] eal/cpuflags: add avx512 two register intersection Kevin Laatz
2020-03-25  8:36 ` [dpdk-dev] [PATCH 00/17] Add CPU flags David Marchand
2020-03-25 11:10 ` [dpdk-dev] [PATCH v2] eal/cpuflags: add x86 based cpu flags Kevin Laatz
2020-03-27 12:24   ` David Marchand
2020-03-27 13:18     ` Van Haaren, Harry
2020-03-27 15:04       ` David Marchand
2020-03-27 13:44     ` Neil Horman
2020-03-27 14:15       ` Thomas Monjalon
2020-03-27 14:32         ` Van Haaren, Harry
2020-03-27 14:36           ` Ray Kinsella [this message]
2020-03-27 15:19             ` Thomas Monjalon
2020-03-30 12:15   ` [dpdk-dev] [PATCH v3] " Kevin Laatz
2020-04-16 10:08     ` Van Haaren, Harry
2020-04-16 11:00     ` [dpdk-dev] [PATCH v4] " Kevin Laatz
2020-04-25 16:04       ` Thomas Monjalon
2020-04-27  9:22         ` Kinsella, Ray
2020-04-27  9:27         ` Ray Kinsella
2020-04-27  9:31           ` Laatz, Kevin
2020-04-27  9:35             ` Ray Kinsella
2020-04-27 10:08               ` Laatz, Kevin
2020-04-27 12:31           ` Thomas Monjalon
2020-04-27 13:58             ` Ray Kinsella
2020-04-29 11:22               ` Neil Horman
2020-04-30  7:59                 ` Ray Kinsella
2020-04-28 12:40       ` [dpdk-dev] [PATCH v5] " Kevin Laatz
2020-04-28 16:39         ` Ray Kinsella
2020-04-28 18:11           ` Laatz, Kevin
2020-04-28 19:55             ` Thomas Monjalon
2020-04-28 19:58           ` Stephen Hemminger
2020-04-29 11:39           ` David Marchand
2020-04-30 10:02             ` Ray Kinsella
2020-05-07 13:00               ` Thomas Monjalon

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