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 3E3EDC35280 for ; Thu, 7 May 2020 22:03:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D9F120A8B for ; Thu, 7 May 2020 22:03:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QbA/yQWX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726480AbgEGWDo (ORCPT ); Thu, 7 May 2020 18:03:44 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:60872 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726437AbgEGWDo (ORCPT ); Thu, 7 May 2020 18:03:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588889022; 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=aspV1wJ37EFxEstXvcVEniumgTmeoY91YcA15b/xS8E=; b=QbA/yQWX1YTDOpRGsLtv3qq4JNov4p8byZ19kTWs/fcvWuuU5uL/Sw745ylXS9HpS8LcWK yTQOx53SWulCiZo8Y90mrC8xXRYLoHQNFV3lPQsYaN0j/ES55lfSCaD1z351xSzKPnWZEw +1wDtnXXkNK7/BdHGQsZVjt+Ltcg0pI= 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-474-LL_F_fyvPrOgRP04awRMaA-1; Thu, 07 May 2020 18:03:39 -0400 X-MC-Unique: LL_F_fyvPrOgRP04awRMaA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 63581180081D; Thu, 7 May 2020 22:03:38 +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 AED8B579AD; Thu, 7 May 2020 22:03:34 +0000 (UTC) Date: Thu, 7 May 2020 16:03:34 -0600 From: Alex Williamson To: Peter Xu Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, jgg@ziepe.ca Subject: Re: [PATCH v2 2/3] vfio-pci: Fault mmaps to enable vma tracking Message-ID: <20200507160334.4c029518@x1.home> In-Reply-To: <20200507214744.GP228260@xz-x1> References: <158871401328.15589.17598154478222071285.stgit@gimli.home> <158871569380.15589.16950418949340311053.stgit@gimli.home> <20200507214744.GP228260@xz-x1> 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 10.5.11.13 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 7 May 2020 17:47:44 -0400 Peter Xu wrote: > Hi, Alex, > > On Tue, May 05, 2020 at 03:54:53PM -0600, Alex Williamson wrote: > > +/* > > + * Zap mmaps on open so that we can fault them in on access and therefore > > + * our vma_list only tracks mappings accessed since last zap. > > + */ > > +static void vfio_pci_mmap_open(struct vm_area_struct *vma) > > +{ > > + zap_vma_ptes(vma, vma->vm_start, vma->vm_end - vma->vm_start); > > A pure question: is this only a safety-belt or it is required in some known > scenarios? It's not required. I originally did this so that I'm not allocating a vma_list entry in a path where I can't return error, but as Jason suggested I could zap here only in the case that I do encounter that allocation fault. However I still like consolidating the vma_list handling to the vm_ops .fault and .close callbacks and potentially we reduce the zap latency by keeping the vma_list to actual users, which we'll get to eventually anyway in the VM case as memory BARs are sized and assigned addresses. > In all cases: > > Reviewed-by: Peter Xu Thanks! Alex