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dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728496AbeI1Cyd (ORCPT ); Thu, 27 Sep 2018 22:54:33 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:42947 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727265AbeI1Cyd (ORCPT ); Thu, 27 Sep 2018 22:54:33 -0400 Received: by mail-pf1-f195.google.com with SMTP id l9-v6so2680189pff.9 for ; Thu, 27 Sep 2018 13:34:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fzP0SCHNefleytqhr8i61IkjqrEe7aWu5vzjf0fqhzQ=; b=oPPTbFefc2IT+lsvPohsztZ8FLRxP+oohgG2IjAfsyihGUF7gPvrWdrFW9ATB2o0kJ BuHWTSsLW+Oqvhlo7P79tDRteb1zQ7mtVO42rW9fn7uJE7Sw6OQ6Dlqj4HMF1SUTJnOt RIUo+A+6AsYIfor3J2ua72JDgmsDTiD+lunyBXUiUAcj9vq0ZpJJNHMs/GHNgTv26+mS lye0rRTtAmaKzbH5jz8FAs7MY0PkpKDG7Q3fZ5tMqLBdIKoZVt9lf5TNXzGqgvK/WuD3 iBjRlTEpKKr+I6RISbrv2GZpbAg6ot6zX4UTVBNbHDC79AiV5MJbgZwSoBR5k7P/rQnJ 7pgg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=fzP0SCHNefleytqhr8i61IkjqrEe7aWu5vzjf0fqhzQ=; b=MqQs7EHKgvSvMiQWHx9gXy5gDuClTbDN3OUeRuVejbqCg+VgW4F41C3KW6cWvLKh4/ JRdaWM41Lo4+RYdeQotZopgymjHAk11T12HgJ1z5GGLVhL/U7Ozz+W20HvM3ynpSAN59 yILcIiOyVNsDPOWuqKbyGWVo+ExRm4vfUZCsEyYl6LxoixEcTnuOfQTLhJxG/RETY5Yc 8fAv3YfxvaCtWuHAy7EVshHQGvw+vjzO/Cq90ZFWyNEhnO+uvDGerN6Nwwgy+rB+OgDZ o9tVMOFc17a+DoIC4kt1CFE4Onz8gQHmancdsQEfEx01gmdaaWrlATdY2vLW7BXXNZ9h M0UQ== X-Gm-Message-State: ABuFfog3ko/+7fzwZcUE3kEWkXPkquRgvqPFu8UxPsWqJdsPsX52LpL2 T+vY0eIyDKmUvpw7/6cHmIlgnv+nZOt2C2OLurT6PA== X-Google-Smtp-Source: ACcGV63bhOpqhE+63/CyxVp1zH2P8mMNVFpp7bSoQ8BPPd9rb5VYSy97FLBxQxpwtXu5gym2J2uqp2loNm5rJsekEDA= X-Received: by 2002:a17:902:b611:: with SMTP id b17-v6mr12686708pls.217.1538080467557; Thu, 27 Sep 2018 13:34:27 -0700 (PDT) MIME-Version: 1.0 References: <20180924195716.30848-1-natechancellor@gmail.com> <20180924222737.GA26973@flashbox> <20180925023722.GA32600@ziepe.ca> <20180927010803.GA7640@flashbox> <20180927044826.GC24889@ziepe.ca> <20180927202849.GA11120@flashbox> In-Reply-To: <20180927202849.GA11120@flashbox> From: Nick Desaulniers Date: Thu, 27 Sep 2018 13:34:16 -0700 Message-ID: Subject: Re: [PATCH] IB/mlx4: Avoid implicit enumerated type conversion To: Nathan Chancellor Cc: jgg@ziepe.ca, dledford@redhat.com, linux-rdma@vger.kernel.org, LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 27, 2018 at 1:28 PM Nathan Chancellor wrote: > > On Thu, Sep 27, 2018 at 01:13:31PM -0700, Nick Desaulniers wrote: > > On Wed, Sep 26, 2018 at 9:48 PM Jason Gunthorpe wrote: > > > > > > On Wed, Sep 26, 2018 at 06:08:03PM -0700, Nathan Chancellor wrote: > > > > On Mon, Sep 24, 2018 at 08:37:22PM -0600, Jason Gunthorpe wrote: > > > > > On Mon, Sep 24, 2018 at 03:29:38PM -0700, Nick Desaulniers wrote: > > > > > > On Mon, Sep 24, 2018 at 3:27 PM Nathan Chancellor > > > > > > wrote: > > > > > > > > > > > > > > On Mon, Sep 24, 2018 at 03:24:36PM -0700, Nick Desaulniers wrote: > > > > > > > > On Mon, Sep 24, 2018 at 12:57 PM Nathan Chancellor > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > Clang warns when one enumerated type is implicitly converted to another. > > > > > > > > > > > > > > > > > > drivers/infiniband/hw/mlx4/mad.c:1811:41: warning: implicit conversion > > > > > > > > > from enumeration type 'enum mlx4_ib_qp_flags' to different enumeration > > > > > > > > > type 'enum ib_qp_create_flags' [-Wenum-conversion] > > > > > > > > > qp_init_attr.init_attr.create_flags = MLX4_IB_SRIOV_TUNNEL_QP; > > > > > > > > > ~ ^~~~~~~~~~~~~~~~~~~~~~~ > > > > > > > > > > > > > > > > > > drivers/infiniband/hw/mlx4/mad.c:1819:41: warning: implicit conversion > > > > > > > > > from enumeration type 'enum mlx4_ib_qp_flags' to different enumeration > > > > > > > > > type 'enum ib_qp_create_flags' [-Wenum-conversion] > > > > > > > > > qp_init_attr.init_attr.create_flags = MLX4_IB_SRIOV_SQP; > > > > > > > > > ~ ^~~~~~~~~~~~~~~~~ > > > > > > > > > > > > > > > > > > The type mlx4_ib_qp_flags explicitly provides supplemental values to the > > > > > > > > > type ib_qp_create_flags. Make that clear to Clang by changing the > > > > > > > > > create_flags type to u32. > > > > > > > > > > > > > > > > > > Reported-by: Nick Desaulniers > > > > > > > > > Signed-off-by: Nathan Chancellor > > > > > > > > > include/rdma/ib_verbs.h | 2 +- > > > > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > > > > > > > > > diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h > > > > > > > > > index e463d3007a35..f6f4d9e3c8ed 100644 > > > > > > > > > +++ b/include/rdma/ib_verbs.h > > > > > > > > > @@ -1149,7 +1149,7 @@ struct ib_qp_init_attr { > > > > > > > > > struct ib_qp_cap cap; > > > > > > > > > enum ib_sig_type sq_sig_type; > > > > > > > > > enum ib_qp_type qp_type; > > > > > > > > > - enum ib_qp_create_flags create_flags; > > > > > > > > > + u32 create_flags; > > > > > > > > > > > > > > > > I think it might be better to just have explicit casts at the > > > > > > > > assignment. What do the maintainers think? > > > > > > > > > > > > > > > > > > > > > > That's fine with me, I tend to explicitly cast if it is only one > > > > > > > location but it certainly makes sense in this case as well. I'll > > > > > > > wait for the maintainers to weigh in before sending a v2. > > > > > > > > > > > > Yeah, I mean my opinion on this might seem arbitrary, but based on the > > > > > > pattern and the comment in ib_qp_create_flags, those enum values are > > > > > > reserved to be "subclassed" in a sense, so they should always be in > > > > > > sync or this code will have bigger problems. > > > > > > > > > > One should not use an 'enum' type name for bitfield storage, as once > > > > > you start or'ing things together the values no longer fall on the > > > > > enum. Some compilers and tools even give warnings in this case, ie > > > > > > > > > > enum x foo = X_A | X_B; > > > > > > > > > > Is an assignment from 'int' to an 'enum x' with an implicit cast. > > > > > > > > > > For this reason, usually bitfield enum declarations should be > > > > > anonymous. > > > > > > > > > > Jason > > > > > > > > Hi Jason, > > > > > > > > I apologize for not understanding but how should I adjust my patch so > > > > that it is acceptable? Do you want the explicit casts like Nick > > > > suggested? > > > > > > No, I think your original patch is fine, I was waiting to see if you > > > or Nick disagreed with my assessment on bitfields.. > > > > It wasn't clear to me whether you were ack'ing or nack'ing the patch. > > If we don't change the patch to explicit casts, shouldn't the change > > be to make create_flags an int? (note: signedness) > > > > -- > > Thanks, > > ~Nick Desaulniers > > Neither ib_qp_create_flags nor mlx4_ib_qp_flags have negative values, is > signedness necessary? enums are by default restricted to the range of ints. It's not right to tie these "anonymous enums" to a specific width and signedness other than int. -- Thanks, ~Nick Desaulniers