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 ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9CD88C76196 for ; Mon, 3 Apr 2023 17:28:13 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id E48552B01A for ; Mon, 3 Apr 2023 17:28:12 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id D198E9863FA for ; Mon, 3 Apr 2023 17:28:12 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id BF9C09863DF; Mon, 3 Apr 2023 17:28:12 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-ID: Sender: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id AE9219863E5 for ; Mon, 3 Apr 2023 17:28:12 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: OnKnnswpPsym7jPmr0t3QA-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680542889; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=1GlRrkyZzim01GGc7lyDWxnpW7+xPDIXk9E9MQU++zc=; b=ua8doiTGJOR6bDIWLBQ33lk/iUVraVXuP5DbC4pJQiPoGQM+6NaHnKkKnvZoEo8cMx kUzgwAbtFf7gNXZBv3AVZnT+9Sd31j/ecFCK5SJpX1e1GKmDU7m+Hpvh4VlwUzni33Tv GArlEcmR0ttyA6YgpcDFP5Ymurq46xBmvUtyv3A86o/fbvOfvgpEZGVJbcmaYPR9Hx82 8MLVj/j7VXrXGMkxM+ovrsXbHp/teRynHhRJl+OavEwDFeNASHmpIFMVFQRrFpHRcb1N /uzL6W/c8jxchlyLYLHjjkSbPU7C4ZpxLipmgAyeb5yf2CCXdcqLffGb2z9aBm8deU8w Ck2A== X-Gm-Message-State: AAQBX9ezmC1Fd2p6qJ/Ilvc8tgoEmiKD4hZ5VL0c23Vdk7WrPXktPmab ge8rkgZKH9Wkj9Kdc5wuBpD1/oed9UBq9SSzcSMcRwyjMUcGTyRbzgRsew16r5980AcdxJ02Z2Z +7t7sT3J7aTry97F8oqQ9n8sP6TuN X-Received: by 2002:a17:906:f190:b0:931:a321:7640 with SMTP id gs16-20020a170906f19000b00931a3217640mr39094898ejb.74.1680542889526; Mon, 03 Apr 2023 10:28:09 -0700 (PDT) X-Google-Smtp-Source: AKy350YG4bUnwfTLO8tAPuP8GzcE/cpXQsXY5czlxpJ5iZo8wEme8+ol7ewV0/U72DtQhc5aIWEgBw== X-Received: by 2002:a17:906:f190:b0:931:a321:7640 with SMTP id gs16-20020a170906f19000b00931a3217640mr39094877ejb.74.1680542889198; Mon, 03 Apr 2023 10:28:09 -0700 (PDT) Date: Mon, 3 Apr 2023 13:28:03 -0400 From: "Michael S. Tsirkin" To: Parav Pandit Cc: "virtio-dev@lists.oasis-open.org" , "cohuck@redhat.com" , "virtio-comment@lists.oasis-open.org" , Shahaf Shuler Message-ID: <20230403132442-mutt-send-email-mst@kernel.org> References: <20230330225834.506969-1-parav@nvidia.com> <20230331024500-mutt-send-email-mst@kernel.org> <0dcd9907-4bb0-ef0d-678d-5bc8f0ded9ec@nvidia.com> <20230403105050-mutt-send-email-mst@kernel.org> <20230403110320-mutt-send-email-mst@kernel.org> <20230403111735-mutt-send-email-mst@kernel.org> <20230403113130-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [virtio-dev] Re: [PATCH 00/11] Introduce transitional mmr pci device On Mon, Apr 03, 2023 at 03:47:56PM +0000, Parav Pandit wrote: > > > > From: Michael S. Tsirkin > > Sent: Monday, April 3, 2023 11:34 AM > > > Another is that we can actually work around legacy bugs in the hypervisor. For > > example, atomicity and alignment bugs do not exist under DMA. Consider MAC > > field, writeable in legacy. Problem this write is not atomic, so there is a window > > where MAC is corrupted. If you do MMIO then you just have to copy this bug. > > If you do DMA then hypervisor can buffer all of MAC and send to device in one > > go. > I am familiar with this bug. > Users feedback that we received so far has kernels with driver support that uses CVQ for setting the mac address on legacy device. > So, it may help but not super important. > > Also, if I recollect correctly, the mac address is configuring bit early in if-scripts sequence before bringing up the interface. > So, haven't seen real issue around it. It's an example, there are other bugs in legacy interfaces. Take inability to decline feature negotiation as an example. With transport vq we can fail at transport level and hypervisor can decide what to do, such as stopping guest or unplugging device, etc. So something like a vq would be a step up. I would like to understand the performance angle though. What you describe is pretty bad. -- MST --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org