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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 8EDE0C433E0 for ; Tue, 9 Feb 2021 16:21:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C18064EB4 for ; Tue, 9 Feb 2021 16:21:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232592AbhBIQUq (ORCPT ); Tue, 9 Feb 2021 11:20:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:40962 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232470AbhBIQUn (ORCPT ); Tue, 9 Feb 2021 11:20:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612887557; 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=rs1U26YidrsL9SDdBBzeFvyIeFC5YMnTPS33wvzZgOY=; b=MC2FyTjQuN33zwifwEeXwSLla+U2VEwZwVQ+PFFOcy+aLiq6WYSFc24pDXZsDAlMAlqkEh fYW1OMPIoLh0Tj86oxnVnvNSDij6Eo9nXPpixO2zYpU3xYZWMVfb0Tay4KBy/dGRl5sZbN iMV0eeuJd/s5k/+lKexqRhWqotBEpak= 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-203-QEcwZ5tpOYCF3PFLRISnBg-1; Tue, 09 Feb 2021 11:19:15 -0500 X-MC-Unique: QEcwZ5tpOYCF3PFLRISnBg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7EA11C7440; Tue, 9 Feb 2021 16:19:13 +0000 (UTC) Received: from thuth.remote.csb (ovpn-114-56.ams2.redhat.com [10.36.114.56]) by smtp.corp.redhat.com (Postfix) with ESMTP id 46DDA171F4; Tue, 9 Feb 2021 16:19:09 +0000 (UTC) Subject: Re: [kvm-unit-tests PATCH] s390x: Workaround smp stop and store status race To: Janosch Frank , Claudio Imbrenda Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, david@redhat.com References: <20210209141554.22554-1-frankja@linux.ibm.com> <20210209170804.75d1fc9d@ibm-vm> From: Thomas Huth Message-ID: Date: Tue, 9 Feb 2021 17:19:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 09/02/2021 17.14, Janosch Frank wrote: > On 2/9/21 5:08 PM, Claudio Imbrenda wrote: >> On Tue, 9 Feb 2021 09:15:54 -0500 >> Janosch Frank wrote: >> >>> KVM and QEMU handle a SIGP stop and store status in two steps: >>> 1) Stop the CPU by injecting a stop request >>> 2) Store when the CPU has left SIE because of the stop request >>> >>> The problem is that the SIGP order is already considered completed by >>> KVM/QEMU when step 1 has been performed and not once both have >>> completed. In addition we currently don't implement the busy CC so a >>> kernel has no way of knowing that the store has finished other than >>> checking the location for the store. >>> >>> This workaround is based on the fact that for a new SIE entry (via the >>> added smp restart) a stop with the store status has to be finished >>> first. >>> >>> Correct handling of this in KVM/QEMU will need some thought and time. >> >> do I understand correctly that you are here "fixing" the test by not >> triggering the KVM bug? Shouldn't we try to trigger as many bugs as >> possible instead? > > This is not a bug, it's missing code :-) > > We trigger a higher number of bugs by running tests and this workaround > does exactly that by letting Thomas use the smp test in the CI again. Alternatively, we could use report_xfail here to make the test pass, but still have the problem reported so that we do not forget to fix it later. Thomas