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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 531D7C25B07 for ; Fri, 5 Aug 2022 17:26:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241156AbiHER05 (ORCPT ); Fri, 5 Aug 2022 13:26:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236448AbiHER04 (ORCPT ); Fri, 5 Aug 2022 13:26:56 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7F1F318387 for ; Fri, 5 Aug 2022 10:26:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659720414; 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=Ao0gkuMRfLYr7o7jS1lx9srHmYWP666Jf7PyQa+IiRM=; b=UTOEmjyy4wz9LnzMq0WArvoCpIfa2pU3dtBG0KayLX/x99yVn/XvvssnbKpv0G5UzoT2Vq BIw39Ov8I8L53VsTASniCaU79jyRtcyb6VIgIM/QTzvLLCi/CtS+uZQFpDlz9UuKHYH9O7 mKkIpVyp9yyiEgcYg+FtpzIo7puklqM= Received: from mail-il1-f199.google.com (mail-il1-f199.google.com [209.85.166.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-61-moHSVsQlOgqgm1lHGoVWUA-1; Fri, 05 Aug 2022 13:26:53 -0400 X-MC-Unique: moHSVsQlOgqgm1lHGoVWUA-1 Received: by mail-il1-f199.google.com with SMTP id i8-20020a056e020d8800b002d931252904so2050543ilj.23 for ; Fri, 05 Aug 2022 10:26:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-message-state :from:to:cc; bh=Ao0gkuMRfLYr7o7jS1lx9srHmYWP666Jf7PyQa+IiRM=; b=3CZswTSOR/jPSqHWvhjEi1m9Rky//R7DpH47X1yKJF4RI7kLJU18Hk7BADwbUrRkc7 HQblG5Sul/hR00Ef9ryWYTBu3KvLhKGtEOmKG2UOaRmQkb+UbGYkX+6MBD0pYzoZMJ3J 7hL+V5dtiA/h8AvWbwMfoJgizVrCycbGhuCcmGDabCw9gYLRSCXd7CUWaz5vbip80c5t qDWM+5p+3IR0QgjOjNBWqQnIJUDdD+u8Jtezod/nRZ+FVfj5Q8S5Pk9yKv7afr6Z1err luhybKAATQvxGUBrXztRphovEP5YG/S3P40gHmCbdvGo5/Uo9bFNSiUvCGnQ2t6tGzh+ sgGA== X-Gm-Message-State: ACgBeo19zNegrrbUr2MgQQTPc9ez96RcC1z9wxmlm1VUVavSjSikXM4w Cm8ll7JXsttkF/mRK0eLWyi5JuokZSWN3cqiZykkiWQdefaowc+FlRlxuzMFzkNkEX7fbGYtE68 gusDhw0Fwrmk3BhJGy9nbtjo7 X-Received: by 2002:a02:cb11:0:b0:342:9092:f529 with SMTP id j17-20020a02cb11000000b003429092f529mr3468004jap.135.1659720412523; Fri, 05 Aug 2022 10:26:52 -0700 (PDT) X-Google-Smtp-Source: AA6agR7imir4f1KMO2BHT01KzYt7aLZmkCLQFcKAIujsjO/VpRceEcJxlfKcgWJITRUJJrp3H1EaVA== X-Received: by 2002:a02:cb11:0:b0:342:9092:f529 with SMTP id j17-20020a02cb11000000b003429092f529mr3467988jap.135.1659720412277; Fri, 05 Aug 2022 10:26:52 -0700 (PDT) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id y14-20020a056602164e00b0067bb431f360sm2063532iow.48.2022.08.05.10.26.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Aug 2022 10:26:51 -0700 (PDT) Date: Fri, 5 Aug 2022 11:26:50 -0600 From: Alex Williamson To: Bjorn Helgaas Cc: "Arinzon, David" , "linux-pci@vger.kernel.org" , "Dagan, Noam" , "Agroskin, Shay" , "Brandes, Shai" , "Kiyanovski, Arthur" , "mk@semihalf.com" , Cornelia Huck , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: vfio/pci - uAPI for WC Message-ID: <20220805112650.5c13f9a3.alex.williamson@redhat.com> In-Reply-To: <20220805160545.GA1020364@bhelgaas> References: <20220805160545.GA1020364@bhelgaas> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 5 Aug 2022 11:05:45 -0500 Bjorn Helgaas wrote: > [+cc Alex, Cornelia, kvm, lkml (from "get_maintainer.pl drivers/vfio") > and rewrapped for plain-text readability] > On Thu, Aug 04, 2022 at 09:47:36AM +0000, Arinzon, David wrote: > > Hi, > > > > There's currently no mechanism for vfio that exposes WC-related > > operations (check if memory is WC capable, ask to WC memory) to user > > space module entities, such as DPDK, for example. > > > > This topic has been previously discussed in [1], [2] and [3], but > > there was no follow-up. > > > > This capability is very useful for DPDK, specifically to the DPDK > > ENA driver that uses vfio-pci, which requires memory to be WC on the > > TX path. Without WC, higher CPU utilization and performance > > degradation are observed. > > > > In the above mentioned discussions, three options were suggested: > > sysfs, ioctl, mmap extension (extra attributes). > > > > Was there any progress on this area? Is there someone who's looking > > into this? IIRC, much of the discussion was related to VM use cases on ARM and they may have found alternate ways to do things more like x86. I'm not aware of any current development towards a uAPI change to enable this. Thanks, Alex