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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 2D9AEC433DF for ; Thu, 14 May 2020 15:22:08 +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 EAE5520657 for ; Thu, 14 May 2020 15:22:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="X+1y4xEp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EAE5520657 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]:49408 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jZFgV-0005BR-66 for qemu-devel@archiver.kernel.org; Thu, 14 May 2020 11:22:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48282) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jZFex-0002eT-2o for qemu-devel@nongnu.org; Thu, 14 May 2020 11:20:31 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:44167 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jZFew-0003IS-6z for qemu-devel@nongnu.org; Thu, 14 May 2020 11:20:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589469628; 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=tDIXc0CCE1Ocf+J9K9gV4w4fLq+QlPigwwJGeIWaaAY=; b=X+1y4xEpu6EeDWneWoTsUdQbqXBTaSrNhDI2KvyE5w6ZyQ1sBovt+k8HNtBy0t+R+2AMHq bexmx25YEhHnnjxZ8A9VNNDs1zB/osJubz2Ijx38XEJEYDPxhxVflbfduEiUGmudTB4+jC X45RPNp/figDOYSv56g760xlgGGStZU= 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-362-UzWEHQOMOOyvDGc9Ipfffw-1; Thu, 14 May 2020 11:20:27 -0400 X-MC-Unique: UzWEHQOMOOyvDGc9Ipfffw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0871319057A1; Thu, 14 May 2020 15:20:26 +0000 (UTC) Received: from gondolin (unknown [10.40.192.240]) by smtp.corp.redhat.com (Postfix) with ESMTP id CB9BB5D9E8; Thu, 14 May 2020 15:20:24 +0000 (UTC) Date: Thu, 14 May 2020 17:20:21 +0200 From: Cornelia Huck To: Jared Rossi Subject: Re: [PATCH v2 1/1] vfio-ccw: allow non-prefetch ORBs Message-ID: <20200514172021.5a66bc56.cohuck@redhat.com> In-Reply-To: <20200512181535.18630-2-jrossi@linux.ibm.com> References: <20200512181535.18630-1-jrossi@linux.ibm.com> <20200512181535.18630-2-jrossi@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 22:25:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: Eric Farman , qemu-s390x@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 12 May 2020 14:15:35 -0400 Jared Rossi wrote: > Remove the explicit prefetch check when using vfio-ccw devices. > This check does not trigger in practice as all Linux channel programs > are intended to use prefetch. > > It is no longer required to force the PFCH flag when using vfio-ccw > devices. That's not quite true: Only kernels that include the currently-queued patch do not require it. Maybe "Newer Linux kernel versions do not require to force the PFCH flag with vfio-ccw devices anymore." ? > > Signed-off-by: Jared Rossi > --- > hw/vfio/ccw.c | 13 +++---------- > 1 file changed, 3 insertions(+), 10 deletions(-) > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c > index 50cc2ec75c..e649377b68 100644 > --- a/hw/vfio/ccw.c > +++ b/hw/vfio/ccw.c > @@ -74,16 +74,9 @@ static IOInstEnding vfio_ccw_handle_request(SubchDev *sch) > struct ccw_io_region *region = vcdev->io_region; > int ret; > > - if (!(sch->orb.ctrl0 & ORB_CTRL0_MASK_PFCH)) { > - if (!(vcdev->force_orb_pfch)) { > - warn_once_pfch(vcdev, sch, "requires PFCH flag set"); > - sch_gen_unit_exception(sch); > - css_inject_io_interrupt(sch); > - return IOINST_CC_EXPECTED; > - } else { > - sch->orb.ctrl0 |= ORB_CTRL0_MASK_PFCH; > - warn_once_pfch(vcdev, sch, "PFCH flag forced"); > - } > + if (!(sch->orb.ctrl0 & ORB_CTRL0_MASK_PFCH) && vcdev->force_orb_pfch) { > + sch->orb.ctrl0 |= ORB_CTRL0_MASK_PFCH; > + warn_once_pfch(vcdev, sch, "PFCH flag forced"); > } > > QEMU_BUILD_BUG_ON(sizeof(region->orb_area) != sizeof(ORB)); Let me spell out what happens: - PFCH bit set -> no change - PFCH bit not set, but force_orb_pfch set -> no change - neither PFCH bit nor force_orb_pfch set: - older kernels: QEMU makes the request, the kernel rejects it, guest gets a unit exception (same result for the guest as before, only a different code flow) - newer kernels: QEMU makes the request, the kernel forwards the request (logging a rate-limited warning); the result depends on whether the guest actually tries to rewrite the channel program or not I think that is what we want, and I think I'll queue this patch with the tweaked commit message, but I'd like a second opinion. (We should also deprecate force_orb_pfch in the future.)