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 3F644C2D0DB for ; Mon, 20 Jan 2020 13:26:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0F1B422314 for ; Mon, 20 Jan 2020 13:26:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579526796; bh=klYwhSlzXGsDXrYWVAaBb32aIuKy3FUULwLCrFi2k0c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=xsT2HVJI6wRrNQKWpv6rkQFVdfLtJXHCjOGjkQ4PAjLBq1Pe3U/pmC6DJd2rZCANY 0aImeO5FWwcydX3AyD7IUH201kwFhpj45OXAQhACwaLHpeX+wIRiHTcscFAAyccJ1Q 9oJlrVm9ZmmujFoIQw4Ry3wgnIuawlJpwV6BZJm4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726903AbgATN0f (ORCPT ); Mon, 20 Jan 2020 08:26:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:51834 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726619AbgATN0f (ORCPT ); Mon, 20 Jan 2020 08:26:35 -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 6E5E521835; Mon, 20 Jan 2020 13:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579526794; bh=klYwhSlzXGsDXrYWVAaBb32aIuKy3FUULwLCrFi2k0c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FwF+8LB/UCFSgtVn0ih4G4gqnqAVSZjaeZM8Jq/DOgl1pngNGCGMNDMHmbN+bcjoG jyDtt2PLwsQeXv3ysNL8YlYrjJsTVuoR6u4h8bvhUOEOjbjMAtgFDPAIeC3sH32+hp syxisp4DxaTeQ9fFXoP9L8bbkl7qf0+5QIjwN7Fc= 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 1itX4a-000HFR-O1; Mon, 20 Jan 2020 13:26:32 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 20 Jan 2020 13:26:32 +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: <20200120130825.28838-1-drjones@redhat.com> References: <20200120130825.28838-1-drjones@redhat.com> Message-ID: <99903fdb3e0d34cb7957981b484fc28c@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 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. If nobody has a better idea, I'll queue it as is. Thanks, M. -- Jazz is not dead. It just smells funny...