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<875yphigb6.fsf@mdr78.vserver.site> <3365765.som1txNFv6@thomas> <8735kli9s7.fsf@mdr78.vserver.site> User-agent: mu4e 1.4.15; emacs 27.1 From: Ray Kinsella To: Thomas Monjalon 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 In-reply-to: <8735kli9s7.fsf@mdr78.vserver.site> Date: Tue, 15 Feb 2022 08:55:15 -0500 Message-ID: <87zgmsgrp8.fsf@mdr78.vserver.site> MIME-Version: 1.0 Content-Type: text/plain X-AuthUser: mdr@ashroe.eu 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 Ray Kinsella writes: > Thomas Monjalon writes: > >> 14/02/2022 17:06, Ray Kinsella: >>> Thomas Monjalon writes: >>> > 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? >>> >>> Nope - I think we should explicitly exclude MAX values from any >>> ABI guarantee, as being able to change them is key to our be able to >>> evolve DPDK while maintaining ABI stability. >> >> Or we can simply remove the MAX values so there is no confusion. >> >>> Consider what it means applying the ABI policy to a MAX value, you are >>> in effect saying that that no value can be added to this enumeration >>> until the next ABI version, for me this is very restrictive without a >>> solid reason. >> >> I agree it is too much restrictive, that's why I am advocating >> for their removal. > > I think that would be simplest yes - may require some rework of the > sample code though. I will take a look at it. Thinking about this some more - we can't remove the MAX values between now the next stable ABI. So we may need a short term plan, and long term plan. Long term, I agree we look at every _MAX enumeration value and ask do we need it. Short term (until the next ABI), we still need to answer the question do we allow people to change _MAX values? >> >>> >> > 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. -- Regards, Ray K