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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 27837C2D0BF for ; Thu, 5 Dec 2019 15:38:58 +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 EAA4A206DB for ; Thu, 5 Dec 2019 15:38:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="LsAb1Zrn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EAA4A206DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56410 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ictDV-00035Q-3E for qemu-devel@archiver.kernel.org; Thu, 05 Dec 2019 10:38:57 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33409) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1icszt-0004My-EH for qemu-devel@nongnu.org; Thu, 05 Dec 2019 10:24:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1icszr-0008Td-7t for qemu-devel@nongnu.org; Thu, 05 Dec 2019 10:24:52 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:22076 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1icszr-0008Hy-1r for qemu-devel@nongnu.org; Thu, 05 Dec 2019 10:24:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575559488; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=28vuIR0QCWs/l5fQ6tEiLiU+bpxf4rV9hu+K2FhhRz0=; b=LsAb1Zrnf0OmVO8mN96i5DCwkRdg1O7cFOljQ4xsrZ9xej5ZYj7MHACeDIG+sDUWm5jYl1 tKzZWjh0rL7jrc+KXfkUM07y8cnh32S+7MwJgNSc6QD2ndwR+w1ZdS6vBl3ypxAFoMwP3X /z9zfsrt3xQb1LQQ/PkztAaW5cccqdU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-148-ddsrxuWFMfOgy1dXEaes6w-1; Thu, 05 Dec 2019 10:24:47 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5797A107ACCA; Thu, 5 Dec 2019 15:24:46 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-62.ams2.redhat.com [10.36.116.62]) by smtp.corp.redhat.com (Postfix) with ESMTP id 272C75D6A5; Thu, 5 Dec 2019 15:24:41 +0000 (UTC) Subject: Re: [PATCH v3] qga: fence guest-set-time if hwclock not available To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Cornelia Huck , Michael Roth References: <20191205115350.18713-1-cohuck@redhat.com> <5aaa7f3a-e3d1-0057-5fe2-07dea4864bc7@redhat.com> From: Laszlo Ersek Message-ID: Date: Thu, 5 Dec 2019 16:24:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <5aaa7f3a-e3d1-0057-5fe2-07dea4864bc7@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: ddsrxuWFMfOgy1dXEaes6w-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 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: "=?UTF-8?Q?Daniel_P_._Berrang=c3=a9?=" , qemu-devel@nongnu.org, Markus Armbruster Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/05/19 14:05, Philippe Mathieu-Daud=C3=A9 wrote: > Hi Cornelia, > > On 12/5/19 12:53 PM, Cornelia Huck wrote: >> The Posix implementation of guest-set-time invokes hwclock to >> set/retrieve the time to/from the hardware clock. If hwclock >> is not available, the user is currently informed that "hwclock >> failed to set hardware clock to system time", which is quite >> misleading. This may happen e.g. on s390x, which has a different >> timekeeping concept anyway. >> >> Let's check for the availability of the hwclock command and >> return QERR_UNSUPPORTED for guest-set-time if it is not available. >> >> Reviewed-by: Laszlo Ersek >> Reviewed-by: Daniel P. Berrang=C3=A9 >> Reviewed-by: Michael Roth >> Signed-off-by: Cornelia Huck >> --- >> >> v2->v3: >> - added 'static' keyword to hwclock_path >> >> Not sure what tree this is going through; if there's no better place, >> I can also take this through the s390 tree. > > s390 or trivial trees seems appropriate. > >> >> --- >> qga/commands-posix.c | 13 ++++++++++++- >> 1 file changed, 12 insertions(+), 1 deletion(-) >> >> diff --git a/qga/commands-posix.c b/qga/commands-posix.c >> index 1c1a165daed8..0be301a4ea77 100644 >> --- a/qga/commands-posix.c >> +++ b/qga/commands-posix.c >> @@ -156,6 +156,17 @@ void qmp_guest_set_time(bool has_time, int64_t >> time_ns, Error **errp) >> pid_t pid; >> Error *local_err =3D NULL; >> struct timeval tv; >> + static const char hwclock_path[] =3D "/sbin/hwclock"; >> + static int hwclock_available =3D -1; >> + >> + if (hwclock_available < 0) { >> + hwclock_available =3D (access(hwclock_path, X_OK) =3D=3D 0); >> + } >> + >> + if (!hwclock_available) { >> + error_setg(errp, QERR_UNSUPPORTED); > > In include/qapi/qmp/qerror.h we have: > > /* > * These macros will go away, please don't use in new code, and do not > * add new ones! > */ Obviously, the last word on this belongs to Markus (CC'd) -- he added that comment. I'd just like to point out *when* that comment was added: approx. four and half years ago. (See commit 4629ed1e9896.) I've always associated QERR_UNSUPPORTED with QMP interfaces rejecting invocation due to lack of support. I don't think one more instance of QERR_UNSUPPORTED will matter much, when we'll "finally" :) convert or eliminate the other 35! (Yes, I've counted.) In case it's unacceptable to add one more QERR_UNSUPPORTED: what is the official solution that replaces it? I assume it was explained in the series that included commit 4629ed1e9896, but I can't easily tell. (And, there is no "QERR_" match in docs/.) Hmmm, more history digging... In the 4629ed1e9896..v4.2.0-rc4 set of commits, the following commits introduced new instances of QERR_UNSUPPORTED: - e09484efbc9d ("qmp: add QMP interface "query-cpu-model-expansion"", 2016-= 09-06) - 0031e0d68339 ("qmp: add QMP interface "query-cpu-model-comparison"", 2016= -09-06) - b18b6043341d ("qmp: add QMP interface "query-cpu-model-baseline"", 2016-0= 9-06) - 1007a37e2082 ("smbios: filter based on CONFIG_SMBIOS rather than TARGET",= 2017-01-16) - 9f57061c3555 ("acpi: filter based on CONFIG_ACPI_X86 rather than TARGET",= 2017-01-16) - 39164c136cba ("qmp/hmp: add query-vm-generation-id and 'info vm-generatio= n-id' commands", 2017-03-02) - 161a56a9065f ("qga: Add 'guest-get-users' command", 2017-04-26) - 53c58e64d0a2 ("qga: Add `guest-get-timezone` command", 2017-04-27) - e674605f9821 ("qemu-ga: check if utmpx.h is available on the system", 201= 7-07-17) I don't claim that all of those additions have stuck with us, to v4.2.0-rc4. Yet, in general, practice doesn't seem to have followed the intended deprecation. > > Maybe we can replace it by "this feature is not supported on this > architecture"? (or without 'on this architecture'). I think if we replace QERR_UNSUPPORTED with anything, it should be "similarly standardized". (Lack of support for a given QMP interface is pretty common, I think.) Thanks, Laszlo > >> + return; >> + } >> /* If user has passed a time, validate and set it. */ >> if (has_time) { >> @@ -195,7 +206,7 @@ void qmp_guest_set_time(bool has_time, int64_t >> time_ns, Error **errp) >> /* Use '/sbin/hwclock -w' to set RTC from the system time, >> * or '/sbin/hwclock -s' to set the system time from RTC. */ >> - execle("/sbin/hwclock", "hwclock", has_time ? "-w" : "-s", >> + execle(hwclock_path, "hwclock", has_time ? "-w" : "-s", >> NULL, environ); >> _exit(EXIT_FAILURE); >> } else if (pid < 0) { >> >