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Mon, 14 Feb 2022 06:16:01 -0500 (EST) From: Thomas Monjalon To: Ray Kinsella Cc: Ferruh Yigit , Kalesh A P , dev@dpdk.org, ajit.khaparde@broadcom.com, asafp@nvidia.com, David Marchand , Andrew Rybchenko Subject: Re: [dpdk-dev] [PATCH v7 1/4] ethdev: support device reset and recovery events Date: Mon, 14 Feb 2022 12:15:59 +0100 Message-ID: <45691978.XUcTiDjVJD@thomas> In-Reply-To: <878rudiwhb.fsf@mdr78.vserver.site> References: <20201009034832.10302-1-kalesh-anakkur.purayil@broadcom.com> <87sfspiuj1.fsf@mdr78.vserver.site> <878rudiwhb.fsf@mdr78.vserver.site> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org 14/02/2022 11:16, Ray Kinsella: > Ray Kinsella writes: > > Thomas Monjalon writes: > >> 02/02/2022 12:44, Ray Kinsella: > >>> Ferruh Yigit writes: > >>> > On 1/28/2022 12:48 PM, Kalesh A P wrote: > >>> >> --- a/lib/ethdev/rte_ethdev.h > >>> >> +++ b/lib/ethdev/rte_ethdev.h > >>> >> @@ -3818,6 +3818,24 @@ enum rte_eth_event_type { > >>> >> RTE_ETH_EVENT_DESTROY, /**< port is released */ > >>> >> RTE_ETH_EVENT_IPSEC, /**< IPsec offload related event */ > >>> >> RTE_ETH_EVENT_FLOW_AGED,/**< New aged-out flows is detected */ > >>> >> + RTE_ETH_EVENT_ERR_RECOVERING, > >>> >> + /**< port recovering from an error > >>> >> + * > >>> >> + * PMD detected a FW reset or error condition. > >>> >> + * PMD will try to recover from the error. > >>> >> + * Data path may be quiesced and Control path operations > >>> >> + * may fail at this time. > >>> >> + */ > >>> >> + RTE_ETH_EVENT_RECOVERED, > >>> >> + /**< port recovered from an error > >>> >> + * > >>> >> + * PMD has recovered from the error condition. > >>> >> + * Control path and Data path are up now. > >>> >> + * PMD re-configures the port to the state prior to the error. > >>> >> + * Since the device has undergone a reset, flow rules > >>> >> + * offloaded prior to reset may be lost and > >>> >> + * the application should recreate the rules again. > >>> >> + */ > >>> >> RTE_ETH_EVENT_MAX /**< max value of this enum */ > >>> > > >>> > > >>> > Also ABI check complains about 'RTE_ETH_EVENT_MAX' value check, cc'ed more people > >>> > to evaluate if it is a false positive: > >>> > > >>> > > >>> > 1 function with some indirect sub-type change: > >>> > [C] 'function int rte_eth_dev_callback_register(uint16_t, rte_eth_event_type, rte_eth_dev_cb_fn, void*)' at rte_ethdev.c:4637:1 has some indirect sub-type changes: > >>> > parameter 3 of type 'typedef rte_eth_dev_cb_fn' has sub-type changes: > >>> > underlying type 'int (typedef uint16_t, enum rte_eth_event_type, void*, void*)*' changed: > >>> > in pointed to type 'function type int (typedef uint16_t, enum rte_eth_event_type, void*, void*)': > >>> > parameter 2 of type 'enum rte_eth_event_type' has sub-type changes: > >>> > type size hasn't changed > >>> > 2 enumerator insertions: > >>> > 'rte_eth_event_type::RTE_ETH_EVENT_ERR_RECOVERING' value '11' > >>> > 'rte_eth_event_type::RTE_ETH_EVENT_RECOVERED' value '12' > >>> > 1 enumerator change: > >>> > 'rte_eth_event_type::RTE_ETH_EVENT_MAX' from value '11' to '13' at rte_ethdev.h:3807:1 > >>> > >>> I don't immediately see the problem that this would cause. > >>> There are no array sizes etc dependent on the value of MAX for instance. > >>> > >>> Looks safe? > >> > >> We never know how this enum will be used by the application. > >> The max value may be used for the size of an event array. > >> It looks a real ABI issue unfortunately. > > > > Right - but we only really care about it when an array size based on MAX > > is likely to be passed to DPDK, which doesn't apply in this case. I don't completely agree. A developer may assume an event will never exceed MAX value. However, after an upgrade of DPDK without app rebuild, a higher event value may be received in the app, breaking the assumption. Should we consider this case as an ABI breakage? > > I noted that some Linux folks explicitly mark similar MAX values as not > > part of the ABI. > > > > /usr/include/linux/perf_event.h > > 37: PERF_TYPE_MAX, /* non-ABI */ > > 60: PERF_COUNT_HW_MAX, /* non-ABI */ > > 79: PERF_COUNT_HW_CACHE_MAX, /* non-ABI */ > > 87: PERF_COUNT_HW_CACHE_OP_MAX, /* non-ABI */ > > 94: PERF_COUNT_HW_CACHE_RESULT_MAX, /* non-ABI */ > > 116: PERF_COUNT_SW_MAX, /* non-ABI */ > > 149: PERF_SAMPLE_MAX = 1U << 24, /* non-ABI */ > > 151: __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, /* > > non-ABI; internal use */ > > 189: PERF_SAMPLE_BRANCH_MAX_SHIFT /* non-ABI */ > > 267: PERF_TXN_MAX = (1 << 8), /* non-ABI */ > > 301: PERF_FORMAT_MAX = 1U << 4, /* non-ABI */ > > 1067: PERF_RECORD_MAX, /* non-ABI */ > > 1078: PERF_RECORD_KSYMBOL_TYPE_MAX /* non-ABI */ > > 1087: PERF_BPF_EVENT_MAX, /* non-ABI */ > > Any thoughts on similarly annotating all our _MAX enums in the same way? > We could also add a section in the ABI Policy to make it explicit _MAX > enum values are not part of the ABI - what do folks think? Interesting. I am not sure it is always ABI-safe though.