From patchwork Thu May 20 11:34:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cornelia Huck X-Patchwork-Id: 12269761 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 07BA3C43461 for ; Thu, 20 May 2021 11:37:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEE1F60E0B for ; Thu, 20 May 2021 11:37:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241363AbhETLij (ORCPT ); Thu, 20 May 2021 07:38:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:51074 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241559AbhETLgc (ORCPT ); Thu, 20 May 2021 07:36:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621510510; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/Au9nWIMCoQk6wVhEc03Ii+LBKp3hBKUFlVdTr5dd6w=; b=Pf/WCO+14mnhKSYmgXvM3RW5kZJUShxM+qsvwwmLg1jZnRScg48Gw2+lYBIMd38PEtuj2r /zkScVpYmC92CdASWu4XY9ohS+MEiBaNUyan6t85h9S9sRonPL/rFPGFX5VBGCuux80tg2 lwTZJPrwNtySIlkXQeUwpu47N1sZnMI= 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-590-lE_kh2uONVSGYLKc38e_pA-1; Thu, 20 May 2021 07:35:06 -0400 X-MC-Unique: lE_kh2uONVSGYLKc38e_pA-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 F32D5107ACF2; Thu, 20 May 2021 11:35:03 +0000 (UTC) Received: from gondolin.fritz.box (ovpn-113-166.ams2.redhat.com [10.36.113.166]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4F44F10013C1; Thu, 20 May 2021 11:35:02 +0000 (UTC) From: Cornelia Huck To: Heiko Carstens , Vasily Gorbik , Christian Borntraeger Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, Eric Farman , Matthew Rosato , Cornelia Huck Subject: [PULL 3/3] vfio-ccw: Serialize FSM IDLE state with I/O completion Date: Thu, 20 May 2021 13:34:50 +0200 Message-Id: <20210520113450.267893-4-cohuck@redhat.com> In-Reply-To: <20210520113450.267893-1-cohuck@redhat.com> References: <20210520113450.267893-1-cohuck@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Eric Farman Today, the stacked call to vfio_ccw_sch_io_todo() does three things: 1) Update a solicited IRB with CP information, and release the CP if the interrupt was the end of a START operation. 2) Copy the IRB data into the io_region, under the protection of the io_mutex 3) Reset the vfio-ccw FSM state to IDLE to acknowledge that vfio-ccw can accept more work. The trouble is that step 3 is (A) invoked for both solicited and unsolicited interrupts, and (B) sitting after the mutex for step 2. This second piece becomes a problem if it processes an interrupt for a CLEAR SUBCHANNEL while another thread initiates a START, thus allowing the CP and FSM states to get out of sync. That is: CPU 1 CPU 2 fsm_do_clear() fsm_irq() fsm_io_request() vfio_ccw_sch_io_todo() fsm_io_helper() Since the FSM state and CP should be kept in sync, let's make a note when the CP is released, and rely on that as an indication that the FSM should also be reset at the end of this routine and open up the device for more work. Signed-off-by: Eric Farman Acked-by: Matthew Rosato Reviewed-by: Cornelia Huck Message-Id: <20210511195631.3995081-4-farman@linux.ibm.com> Signed-off-by: Cornelia Huck --- drivers/s390/cio/vfio_ccw_drv.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c index 8c625b530035..9b61e9b131ad 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -86,6 +86,7 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work) struct vfio_ccw_private *private; struct irb *irb; bool is_final; + bool cp_is_finished = false; private = container_of(work, struct vfio_ccw_private, io_work); irb = &private->irb; @@ -94,14 +95,21 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work) (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT)); if (scsw_is_solicited(&irb->scsw)) { cp_update_scsw(&private->cp, &irb->scsw); - if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) + if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) { cp_free(&private->cp); + cp_is_finished = true; + } } mutex_lock(&private->io_mutex); memcpy(private->io_region->irb_area, irb, sizeof(*irb)); mutex_unlock(&private->io_mutex); - if (private->mdev && is_final) + /* + * Reset to IDLE only if processing of a channel program + * has finished. Do not overwrite a possible processing + * state if the final interrupt was for HSCH or CSCH. + */ + if (private->mdev && cp_is_finished) private->state = VFIO_CCW_STATE_IDLE; if (private->io_trigger)