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 E369FC3A5A9 for ; Mon, 4 May 2020 18:52:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCAF620661 for ; Mon, 4 May 2020 18:52:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FIqBWDWf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726627AbgEDSw6 (ORCPT ); Mon, 4 May 2020 14:52:58 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:39704 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725981AbgEDSw6 (ORCPT ); Mon, 4 May 2020 14:52:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588618377; 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=nL6lAvx0PZBs0tR/mUzSs6IrJPt6ZBwzzVz2VqiOHPM=; b=FIqBWDWfiNnrJAyhpBKaV4q9+mQnOA7mxKA9H8JVEUWpAUOxd7np6AR22Eib+4MFVWRzTG gWk3P7PPWXhlWeX0Jj9jpDpnyXwJyktFoXjzSjs7oMs5JArLutbOS8Gb/YDNAN/0qT/v2K La7THV/7Y2E011VMMcin/Tn9x27sZiY= 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-239-c41xC3eyMaO8N3yQTQUKsA-1; Mon, 04 May 2020 14:52:55 -0400 X-MC-Unique: c41xC3eyMaO8N3yQTQUKsA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7BB60107ACCD; Mon, 4 May 2020 18:52:54 +0000 (UTC) Received: from x1.home (ovpn-113-95.phx2.redhat.com [10.3.113.95]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3A55A60C80; Mon, 4 May 2020 18:52:54 +0000 (UTC) Date: Mon, 4 May 2020 12:52:53 -0600 From: Alex Williamson To: Cornelia Huck Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vfio-pci: Mask cap zero Message-ID: <20200504125253.3d5f9cbf@x1.home> In-Reply-To: <20200504180916.0e90cad9.cohuck@redhat.com> References: <158836927527.9272.16785800801999547009.stgit@gimli.home> <20200504180916.0e90cad9.cohuck@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 4 May 2020 18:09:16 +0200 Cornelia Huck wrote: > On Fri, 01 May 2020 15:41:24 -0600 > Alex Williamson wrote: > > > There is no PCI spec defined capability with ID 0, therefore we don't > > expect to find it in a capability chain and we use this index in an > > internal array for tracking the sizes of various capabilities to handle > > standard config space. Therefore if a device does present us with a > > capability ID 0, we mark our capability map with nonsense that can > > trigger conflicts with other capabilities in the chain. Ignore ID 0 > > when walking the capability chain, handling it as a hidden capability. > > > > Seen on an NVIDIA Tesla T4. > > > > Signed-off-by: Alex Williamson > > --- > > drivers/vfio/pci/vfio_pci_config.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c > > index 87d0cc8c86ad..5935a804cb88 100644 > > --- a/drivers/vfio/pci/vfio_pci_config.c > > +++ b/drivers/vfio/pci/vfio_pci_config.c > > @@ -1487,7 +1487,7 @@ static int vfio_cap_init(struct vfio_pci_device *vdev) > > if (ret) > > return ret; > > > > - if (cap <= PCI_CAP_ID_MAX) { > > Maybe add a comment: > > /* no PCI spec defined capability with ID 0: hide it */ > Sure. > > > + if (cap && cap <= PCI_CAP_ID_MAX) { > > len = pci_cap_length[cap]; > > if (len == 0xFF) { /* Variable length */ > > len = vfio_cap_len(vdev, cap, pos); > > > > Is there a requirement for caps to be strictly ordered? If not, could > len hold a residual value from a previous iteration? There is no ordering requirement for capabilities, but len is declared non-static with an initial value within the scope of the loop, it's reset every iteration. Thanks, Alex