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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 057FAC433DF for ; Tue, 26 May 2020 09:55:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C913B2073B for ; Tue, 26 May 2020 09:55:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YnKRHgiy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731735AbgEZJzv (ORCPT ); Tue, 26 May 2020 05:55:51 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:21560 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728746AbgEZJzu (ORCPT ); Tue, 26 May 2020 05:55:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590486949; 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=+cQApP9aKEI0EAEIJXWQWFCwQQofjUokxLamDjDh03I=; b=YnKRHgiyDLT7LfC9MAvJie8NceUM5ubHmFqQgXlhnmLexfvAMTHqx1SXB3p4Ay6h4UEG5G 38EA/MvuUlpufAmFBshmmeB5sLCqe6TiuMK+TMt+cwis2YFgIxplytRhQfo6kBd72jGqjw EUaHpi1vtcyGyeQjEAPI6rZlqCdw+rM= 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-206-9HbLNGWxPI6ox2gEn9O8Vg-1; Tue, 26 May 2020 05:55:46 -0400 X-MC-Unique: 9HbLNGWxPI6ox2gEn9O8Vg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1AB651800D42; Tue, 26 May 2020 09:55:45 +0000 (UTC) Received: from gondolin (ovpn-113-77.ams2.redhat.com [10.36.113.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id D4D3110013D5; Tue, 26 May 2020 09:55:43 +0000 (UTC) Date: Tue, 26 May 2020 11:55:41 +0200 From: Cornelia Huck To: Eric Farman Cc: Jared Rossi , Halil Pasic , linux-s390@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC PATCH v2 0/4] vfio-ccw: Fix interrupt handling for HALT/CLEAR Message-ID: <20200526115541.4a11accc.cohuck@redhat.com> In-Reply-To: <20200513142934.28788-1-farman@linux.ibm.com> References: <20200513142934.28788-1-farman@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, 13 May 2020 16:29:30 +0200 Eric Farman wrote: > There was some suggestion earlier about locking the FSM, but I'm not > seeing any problems with that. Rather, what I'm noticing is that the > flow between a synchronous START and asynchronous HALT/CLEAR have > different impacts on the FSM state. Consider: > > CPU 1 CPU 2 > > SSCH (set state=CP_PENDING) > INTERRUPT (set state=IDLE) > CSCH (no change in state) > SSCH (set state=CP_PENDING) > INTERRUPT (set state=IDLE) > INTERRUPT (set state=IDLE) A different question (not related to how we want to fix this): How easily can you trigger this bug? Is this during normal testing with a bit of I/O stress, or do you have a special test case?