From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0668C2D0DB for ; Mon, 20 Jan 2020 13:59:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A3BE021D7E for ; Mon, 20 Jan 2020 13:59:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579528788; bh=igQFmPoiZFVlkBvmT/PwXmP0Kk7D/FPyAdDPnpZIre0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=PuaAFXJvJ6K7l36fVnnU08Mvk+IxU2R19g3OqWZ6BSHIUPuTRxuuoWTvHq3hUTDjK FF9Z9vBOAvCKKCh0K18eHOWBFes+EUxk2Wm6gBwhE1D6fDkWdtmL6H9IODbL80FNxD bZgFjEtfDM8f3bzFYEuGWUbuCwTBXrS3qGuZ+BOQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726798AbgATN7r (ORCPT ); Mon, 20 Jan 2020 08:59:47 -0500 Received: from mail.kernel.org ([198.145.29.99]:41496 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726626AbgATN7r (ORCPT ); Mon, 20 Jan 2020 08:59:47 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B5A2D217F4; Mon, 20 Jan 2020 13:59:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579528786; bh=igQFmPoiZFVlkBvmT/PwXmP0Kk7D/FPyAdDPnpZIre0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=K1GjV258FqS+3P0h9s2XLC12FVVO/SBMI5fwbqXf8VR5eOxwjLBWZkNKdMVlVpC0u 0AWgXqmG6ddPRvN5pemGBcK8Xv/e/j+PNKVHNnjRg5CZkP6jnGHs1VB1/UKeMfvnEb DqTwJnel4pjr1fiLd3I+26+FGiD367+fDdD85IiY= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1itXaj-000HeI-26; Mon, 20 Jan 2020 13:59:45 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 20 Jan 2020 13:59:45 +0000 From: Marc Zyngier To: Andrew Jones Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH] arm64: KVM: Add XXX UAPI notes for swapped registers In-Reply-To: <20200120135129.tgucvvwbeef2q3js@kamzik.brq.redhat.com> References: <20200120130825.28838-1-drjones@redhat.com> <99903fdb3e0d34cb7957981b484fc28c@kernel.org> <20200120135129.tgucvvwbeef2q3js@kamzik.brq.redhat.com> Message-ID: <773360494fdacfbade4b1cc611bc0082@kernel.org> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.8 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2020-01-20 13:51, Andrew Jones wrote: > On Mon, Jan 20, 2020 at 01:26:32PM +0000, Marc Zyngier wrote: >> Hi Andrew, >> >> Many thanks for this. Comments below. >> >> On 2020-01-20 13:08, Andrew Jones wrote: >> > Two UAPI system register IDs do not derive their values from the >> > ARM system register encodings. This is because their values were >> > accidentally swapped. As the IDs are API, they cannot be changed. >> > Add XXX notes to point them out. >> > >> > Suggested-by: Marc Zyngier >> > Signed-off-by: Andrew Jones >> > --- >> > Documentation/virt/kvm/api.txt | 8 ++++++++ >> > arch/arm64/include/uapi/asm/kvm.h | 11 +++++++++-- >> > 2 files changed, 17 insertions(+), 2 deletions(-) >> > >> > diff --git a/Documentation/virt/kvm/api.txt >> > b/Documentation/virt/kvm/api.txt >> > index ebb37b34dcfc..11556fc457c3 100644 >> > --- a/Documentation/virt/kvm/api.txt >> > +++ b/Documentation/virt/kvm/api.txt >> > @@ -2196,6 +2196,14 @@ arm64 CCSIDR registers are demultiplexed by >> > CSSELR value: >> > arm64 system registers have the following id bit patterns: >> > 0x6030 0000 0013 >> > >> > +XXX: Two system register IDs do not follow the specified pattern. >> > These >> > + are KVM_REG_ARM_TIMER_CVAL and KVM_REG_ARM_TIMER_CNT, which map to >> > + system registers CNTV_CVAL_EL0 and CNTVCT_EL0 respectively. These >> > + two had their values accidentally swapped, which means TIMER_CVAL >> > is >> > + derived from the register encoding for CNTVCT_EL0 and TIMER_CNT is >> > + derived from the register encoding for CNTV_CVAL_EL0. As this is >> > + API, it must remain this way. >> >> Is 'XXX' an establiched way of documenting this kind of misfeature? >> I couldn't find any other occurrence in Documentation, but I haven't >> searched very hard. > > I didn't find anything claiming it was the standard way of doing it. I > also considered using 'NOTE', but I was afraid it wouldn't stand out > as a "problem" enough. And, even though 'BUG' would certainly stand > out, > I felt it implied we should be posting a fix. > > Anyway, I'd be happy to change it to whatever the consensus is. My personal preference would be for a big fat "*WARNING*" (with an optional attribute), and a link to a picture of me wearing a brown paper bag on my head. But maybe "WARNING" is enough. Dunno. Anyway, if nobody comes up with a better idea by tomorrow, I'll take it as is. Thanks, M. -- Jazz is not dead. It just smells funny...