From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124])
by inbox.dpdk.org (Postfix) with ESMTP id 4C34EA00C5;
Tue, 15 Feb 2022 14:55:22 +0100 (CET)
Received: from [217.70.189.124] (localhost [127.0.0.1])
by mails.dpdk.org (Postfix) with ESMTP id 13BEB4113E;
Tue, 15 Feb 2022 14:55:21 +0100 (CET)
Received: from mail-108-mta123.mxroute.com (mail-108-mta123.mxroute.com
[136.175.108.123])
by mails.dpdk.org (Postfix) with ESMTP id C721441155
for <dev@dpdk.org>; Tue, 15 Feb 2022 14:55:19 +0100 (CET)
Received: from filter006.mxroute.com ([140.82.40.27] 140.82.40.27.vultr.com)
(Authenticated sender: mN4UYu2MZsgR)
by mail-108-mta123.mxroute.com (ZoneMTA) with ESMTPSA id
17efdaa88520005a20.003 for <dev@dpdk.org>
(version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES128-GCM-SHA256);
Tue, 15 Feb 2022 13:55:18 +0000
X-Zone-Loop: d9d80f828d750649de5ea5d2a0a9b96380edb0110f9d
X-Originating-IP: [140.82.40.27]
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=ashroe.eu;
s=x;
h=Content-Type:MIME-Version:Message-ID:Date:In-reply-to:Subject:Cc:To:
From:References:Sender:Reply-To:Content-Transfer-Encoding:Content-ID:
Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc
:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe:
List-Post:List-Owner:List-Archive;
bh=livecHQE24575xTa7jYFv82neVsaHAb/tgwehuGw8gU=; b=pZRYMWtLfDyLeu+ENZSYVoKRhk
YcnF6u8Y4ZatK7KciEp7xh5kvyUAlT1/x4iiiGW8Yx0r7qkA3f++CO/oTncYNm8WNDQynHn2p1N7j
MR0NhTie32/UTzrSbbC9U4adC7RJg4dr5e0uEjfnl202HdJGCcUAGOZLQtZtQKoiP37YmLN3Ug8ZI
29eTG8LUdxuP+i+8lWjCBcK/zjCOg6S4QzWlCt3CzHDNPgsjT2kQxtCh0DAq72XtWaC0LQ0erfFcX
LO/SZXeFNjfG40eOWHmT2HBIXJyX36tdNCRlTMgvnBxRptxsoDvBgeIMvLNOkS1sBZ2bzmV8r68is
GkaAEwNg==;
References: <20201009034832.10302-1-kalesh-anakkur.purayil@broadcom.com>
<45691978.XUcTiDjVJD@thomas> <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 <mdr@ashroe.eu>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: Ferruh Yigit <ferruh.yigit@intel.com>, Kalesh A P
<kalesh-anakkur.purayil@broadcom.com>, dev@dpdk.org,
ajit.khaparde@broadcom.com, asafp@nvidia.com, David Marchand
<david.marchand@redhat.com>, Andrew Rybchenko
<andrew.rybchenko@oktetlabs.ru>
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 <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
<mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
<mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Ray Kinsella <mdr@ashroe.eu> writes:
> Thomas Monjalon <thomas@monjalon.net> writes:
>
>> 14/02/2022 17:06, Ray Kinsella:
>>> Thomas Monjalon <thomas@monjalon.net> writes:
>>> > 14/02/2022 11:16, Ray Kinsella:
>>> >> Ray Kinsella <mdr@ashroe.eu> writes:
>>> >> > Thomas Monjalon <thomas@monjalon.net> writes:
>>> >> >> 02/02/2022 12:44, Ray Kinsella:
>>> >> >>> Ferruh Yigit <ferruh.yigit@intel.com> 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