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=-2.4 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,USER_AGENT_SANE_1 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 88B58C433E0 for ; Fri, 15 May 2020 17:51:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D3A720727 for ; Fri, 15 May 2020 17:51:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hQnrwFUD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726206AbgEORvW (ORCPT ); Fri, 15 May 2020 13:51:22 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:30629 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726144AbgEORvV (ORCPT ); Fri, 15 May 2020 13:51:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589565080; 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: in-reply-to:in-reply-to:references:references; bh=vanYtfZyXcbovVUz0PsUuXeLhO3F7puLUyYiB1U7kYE=; b=hQnrwFUDXi53z1m00k89XyTxpvIv/5uQcAwN9UgD2eoHDQ7OonZgTwDeIU1JDtqA+WtzRm L4/+cJ0PfXyQrEDYGO3yRRFypdaoo2KflcoyNG/6lWBGCDB43cCbdS1Z9ey4LUT9eb8ET4 nyzFPBe1hDq0VB9IAAOFmJjZGa2jfuk= 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-389-GmCtVheaNcGmxf-ZPupsmw-1; Fri, 15 May 2020 13:51:17 -0400 X-MC-Unique: GmCtVheaNcGmxf-ZPupsmw-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 26E9780183C; Fri, 15 May 2020 17:51:16 +0000 (UTC) Received: from work-vm (ovpn-114-149.ams2.redhat.com [10.36.114.149]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2019E5D9C9; Fri, 15 May 2020 17:51:08 +0000 (UTC) Date: Fri, 15 May 2020 18:51:05 +0100 From: "Dr. David Alan Gilbert" To: David Hildenbrand Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, qemu-s390x@nongnu.org, Richard Henderson , Paolo Bonzini , Eduardo Habkost , "Michael S . Tsirkin" , Juan Quintela Subject: Re: [PATCH v1 07/17] migration/rdma: Use ram_block_discard_set_broken() Message-ID: <20200515175105.GL2954@work-vm> References: <20200506094948.76388-1-david@redhat.com> <20200506094948.76388-8-david@redhat.com> <20200515124501.GE2954@work-vm> <96a58e88-2629-f2ee-5884-38d11e571548@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <96a58e88-2629-f2ee-5884-38d11e571548@redhat.com> User-Agent: Mutt/1.13.4 (2020-02-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org * David Hildenbrand (david@redhat.com) wrote: > On 15.05.20 14:45, Dr. David Alan Gilbert wrote: > > * David Hildenbrand (david@redhat.com) wrote: > >> RDMA will pin all guest memory (as documented in docs/rdma.txt). We want > >> to mark RAM block discards to be broken - however, to keep it simple > >> use ram_block_discard_is_required() instead of inhibiting. > > > > Should this be dependent on whether rdma->pin_all is set? > > Even with !pin_all some will be pinned at any given time > > (when it's registered with the rdma stack). > > Do you know how much memory this is? Is such memory only temporarily pinned? With pin_all not set, only a subset of memory, I think multiple 1MB chunks, are pinned at any one time. > At least with special-cases of vfio, it's acceptable if some memory is > temporarily pinned - we assume it's only the working set of the driver, > which guests will not inflate as long as they don't want to shoot > themselves in the foot. > > This here sounds like the guest does not know the pinned memory is > special, right? Right - for RDMA it's all of memory that's being transferred, and the guest doesn't see when each part is transferred. Dave > -- > Thanks, > > David / dhildenb -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK