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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]:58088 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kIwM7-0005Mf-TE for qemu-devel@archiver.kernel.org; Thu, 17 Sep 2020 12:01:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42880) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kIwI9-0002xU-5b for qemu-devel@nongnu.org; Thu, 17 Sep 2020 11:57:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:57937) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kIwI7-0003L6-21 for qemu-devel@nongnu.org; Thu, 17 Sep 2020 11:57:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600358265; 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:autocrypt:autocrypt; bh=ve4lweGNRoh7zRCRfYavNxOb/nDjD9Sfzrx+XKirtss=; b=C8o7/w2Zr9vKliP7IqojutFN0aXalsCqsO7z44J9n4e7zcZcsDcRDqMmpReeJkSU1XRdTV D7zsA0jEecKX1l39MrsSPGoV7tSJMGFab3njuSg1F7InoR6hw71/kdk1dwYdJCDF16h0uK 3vCyGvBfHf1Nq/BhWRuBWe9mpdxpEFY= 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-42-4RVuI2o1PPSvGMTwosLrBg-1; Thu, 17 Sep 2020 11:57:42 -0400 X-MC-Unique: 4RVuI2o1PPSvGMTwosLrBg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 61E2164177; Thu, 17 Sep 2020 15:57:32 +0000 (UTC) Received: from [10.36.114.153] (ovpn-114-153.ams2.redhat.com [10.36.114.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id E35CA99140; Thu, 17 Sep 2020 15:57:30 +0000 (UTC) Subject: Re: [PATCH v1] s390x/tcg: Implement MONITOR CALL To: Richard Henderson , qemu-devel@nongnu.org References: <20200917115447.10503-1-david@redhat.com> <17b2cca5-f21d-1323-1003-3d9731a698cc@linaro.org> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <17b2cca5-f21d-1323-1003-3d9731a698cc@linaro.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Received-SPF: pass client-ip=63.128.21.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/16 20:51:18 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.997, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Christian Borntraeger , qemu-s390x@nongnu.org, Cornelia Huck , Thomas Huth Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17.09.20 17:33, Richard Henderson wrote: > On 9/17/20 4:54 AM, David Hildenbrand wrote: >> Recent upstream Linux uses the MONITOR CALL instruction for things like >> BUG_ON() and WARN_ON(). We currently inject an operation exception when >> we hit a MONITOR CALL instruction - which is wrong, as the instruction >> is not glued to specific CPU features. >> >> Doing a simple WARN_ON_ONCE() currently results in a panic: >> [ 18.162801] illegal operation: 0001 ilc:2 [#1] SMP >> [ 18.162889] Modules linked in: >> [...] >> [ 18.165476] Kernel panic - not syncing: Fatal exception: panic_on_oops >> >> With a proper implementation, we now get: >> [ 18.242754] ------------[ cut here ]------------ >> [ 18.242855] WARNING: CPU: 7 PID: 1 at init/main.c:1534 [...] >> [ 18.242919] Modules linked in: >> [...] >> [ 18.246262] ---[ end trace a420477d71dc97b4 ]--- >> [ 18.259014] Freeing unused kernel memory: 4220K >> >> To be able to translate it to a NOP easily, mangle the 16 monitor masks >> bits from the cr8 into the TB flags. > > This is a rare situation that does not warrant the use of TB flags. Better to I think it can be used for tracing and such, so quite excessively - but yeah, at least in Linux it should be rare. > unconditionally call helper_monitor_event, and have the helper function test > the runtime value of cr8. If the event is disabled, the helper simply returns. > > It should be simpler to write, as well, not having to do this: > Was too appealing to optimize. Well, doing it in a handler also makes the implementation of monitor-event counting easier. -- Thanks, David / dhildenb