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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 CBB1AC35666 for ; Sat, 22 Feb 2020 19:33:22 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A5C1E206ED for ; Sat, 22 Feb 2020 19:33:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A5C1E206ED Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ilande.co.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45282 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j5aWf-0002B1-UR for qemu-devel@archiver.kernel.org; Sat, 22 Feb 2020 14:33:21 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:52863) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j5aVw-0001cC-MS for qemu-devel@nongnu.org; Sat, 22 Feb 2020 14:32:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j5aVv-000680-Ht for qemu-devel@nongnu.org; Sat, 22 Feb 2020 14:32:36 -0500 Received: from mail.ilande.co.uk ([2001:41c9:1:41f::167]:36406 helo=mail.default.ilande.uk0.bigv.io) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j5aVv-00066z-CT for qemu-devel@nongnu.org; Sat, 22 Feb 2020 14:32:35 -0500 Received: from host86-177-178-1.range86-177.btcentralplus.com ([86.177.178.1] helo=[192.168.1.65]) by mail.default.ilande.uk0.bigv.io with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1j5aW4-00005F-PY; Sat, 22 Feb 2020 19:32:50 +0000 To: jasper.lowell@bt.com, qemu-devel@nongnu.org References: <20200221065015.337915-1-jasper.lowell@bt.com> From: Mark Cave-Ayland Autocrypt: addr=mark.cave-ayland@ilande.co.uk; keydata= mQENBFQJuzwBCADAYvxrwUh1p/PvUlNFwKosVtVHHplgWi5p29t58QlOUkceZG0DBYSNqk93 3JzBTbtd4JfFcSupo6MNNOrCzdCbCjZ64ik8ycaUOSzK2tKbeQLEXzXoaDL1Y7vuVO7nL9bG E5Ru3wkhCFc7SkoypIoAUqz8EtiB6T89/D9TDEyjdXUacc53R5gu8wEWiMg5MQQuGwzbQy9n PFI+mXC7AaEUqBVc2lBQVpAYXkN0EyqNNT12UfDLdxaxaFpUAE2pCa2LTyo5vn5hEW+i3VdN PkmjyPvL6DdY03fvC01PyY8zaw+UI94QqjlrDisHpUH40IUPpC/NB0LwzL2aQOMkzT2NABEB AAG0ME1hcmsgQ2F2ZS1BeWxhbmQgPG1hcmsuY2F2ZS1heWxhbmRAaWxhbmRlLmNvLnVrPokB OAQTAQIAIgUCVAm7PAIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQW8LFb64PMh9f NAgAuc3ObOEY8NbZko72AGrg2tWKdybcMVITxmcor4hb9155o/OWcA4IDbeATR6cfiDL/oxU mcmtXVgPqOwtW3NYAKr5g/FrZZ3uluQ2mtNYAyTFeALy8YF7N3yhs7LOcpbFP7tEbkSzoXNG z8iYMiYtKwttt40WaheWuRs0ZOLbs6yoczZBDhna3Nj0LA3GpeJKlaV03O4umjKJgACP1c/q T2Pkg+FCBHHFP454+waqojHp4OCBo6HyK+8I4wJRa9Z0EFqXIu8lTDYoggeX0Xd6bWeCFHK3 DhD0/Xi/kegSW33unsp8oVcM4kcFxTkpBgj39dB4KwAUznhTJR0zUHf63LkBDQRUCbs8AQgA y7kyevA4bpetM/EjtuqQX4U05MBhEz/2SFkX6IaGtTG2NNw5wbcAfhOIuNNBYbw6ExuaJ3um 2uLseHnudmvN4VSJ5Hfbd8rhqoMmmO71szgT/ZD9MEe2KHzBdmhmhxJdp+zQNivy215j6H27 14mbC2dia7ktwP1rxPIX1OOfQwPuqlkmYPuVwZP19S4EYnCELOrnJ0m56tZLn5Zj+1jZX9Co YbNLMa28qsktYJ4oU4jtn6V79H+/zpERZAHmH40IRXdR3hA+Ye7iC/ZpWzT2VSDlPbGY9Yja Sp7w2347L5G+LLbAfaVoejHlfy/msPeehUcuKjAdBLoEhSPYzzdvEQARAQABiQEfBBgBAgAJ BQJUCbs8AhsMAAoJEFvCxW+uDzIfabYIAJXmBepHJpvCPiMNEQJNJ2ZSzSjhic84LTMWMbJ+ opQgr5cb8SPQyyb508fc8b4uD8ejlF/cdbbBNktp3BXsHlO5BrmcABgxSP8HYYNsX0n9kERv NMToU0oiBuAaX7O/0K9+BW+3+PGMwiu5ml0cwDqljxfVN0dUBZnQ8kZpLsY+WDrIHmQWjtH+ Ir6VauZs5Gp25XLrL6bh/SL8aK0BX6y79m5nhfKI1/6qtzHAjtMAjqy8ChPvOqVVVqmGUzFg KPsrrIoklWcYHXPyMLj9afispPVR8e0tMKvxzFBWzrWX1mzljbBlnV2n8BIwVXWNbgwpHSsj imgcU9TTGC5qd9g= Message-ID: Date: Sat, 22 Feb 2020 19:32:26 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200221065015.337915-1-jasper.lowell@bt.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 86.177.178.1 X-SA-Exim-Mail-From: mark.cave-ayland@ilande.co.uk Subject: Re: [PATCH] hw/ide: Remove status register read side effect X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on mail.default.ilande.uk0.bigv.io) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2001:41c9:1:41f::167 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jsnow@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 21/02/2020 06:50, jasper.lowell@bt.com wrote: > The Linux libATA API documentation mentions that on some hardware, > reading the status register has the side effect of clearing the > interrupt condition. When emulating the generic Sun4u machine running > Solaris 10, the Solaris 10 CMD646 driver exits fatally because of this > emulated side effect. This side effect is likely to not exist on real > CMD646 hardware. > > Signed-off-by: Jasper Lowell > --- > hw/ide/core.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/hw/ide/core.c b/hw/ide/core.c > index 80000eb766..82fd0632ac 100644 > --- a/hw/ide/core.c > +++ b/hw/ide/core.c > @@ -2210,7 +2210,6 @@ uint32_t ide_ioport_read(void *opaque, uint32_t addr) > } else { > ret = s->status; > } > - qemu_irq_lower(bus->irq); > break; > } I don't think that this is correct: from memory when I last looked at this, there were 2 IDE status registers: the one from the original specification which clears the IRQ upon read, and another one in subsequent revisions which allows you to read the value without clearing any pending IRQ. My guess would be that changing this would not only cause QEMU to deviate from the specification, but causes problems in other OSs. ATB, Mark.