From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] bus/pci: forbid VA as IOVA mode if IOMMU address width too small Date: Mon, 8 Jan 2018 07:34:11 -0800 Message-ID: <20180108073411.67f12201@xeon-e3> References: <20180108135127.25869-1-maxime.coquelin@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org, stable@dpdk.org, jianfeng.tan@intel.com, santosh.shukla@caviumnetworks.com, anatoly.burakov@intel.com, thomas@monjalon.net, peterx@redhat.com To: Maxime Coquelin Return-path: Received: from mail-pg0-f65.google.com (mail-pg0-f65.google.com [74.125.83.65]) by dpdk.org (Postfix) with ESMTP id 072E61B1B2 for ; Mon, 8 Jan 2018 16:34:16 +0100 (CET) Received: by mail-pg0-f65.google.com with SMTP id q12so5743327pgt.7 for ; Mon, 08 Jan 2018 07:34:16 -0800 (PST) In-Reply-To: <20180108135127.25869-1-maxime.coquelin@redhat.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Mon, 8 Jan 2018 14:51:27 +0100 Maxime Coquelin wrote: > Intel VT-d supports different address widths for the IOVAs, from > 39 bits to 56 bits. > > While recent processors support at least 48 bits, VT-d emulation > currently only supports 39 bits. It makes DMA mapping to fail in this > case when using VA as IOVA mode, as user-space virtual addresses uses > up to 47 bits (see kernel's Documentation/x86/x86_64/mm.txt). > > This patch parses VT-d CAP register value available in sysfs, and > forbid VA as IOVA mode if the GAW is 39 bits or unknown. > > Fixes: f37dfab21c98 ("drivers/net: enable IOVA mode for Intel PMDs") > > Cc: stable@dpdk.org > Signed-off-by: Maxime Coquelin > --- > Hi, > > I'm not super happy with the patch as it does platform specific things in > generic code, but there are no placeholder for IOMMU/VT-d at the moment. > > As this patch is to be backported to v17.11 LTS, it cannot be a big rework. > > If you have some suggestion to improve it, please let me know. > > The fix is quite urgent, as guest device assignment with vIOMMU is broken in > mainline & v17.11 LTS. > > Advantage of this fix over forbidding VA as IOVA when running in emulation is > that VT-d emulation will soon support 48 bits, so this is future proof. Also, > VT-d spec supports 39 bits, so we could have physical CPUs supporting it, even > if I don't know any. > > Thanks, > Maxime You are assumming that if IOMMU is present that it is being used (ie VFIO). What about the case of direct access to PF device via IGB_UIO? > +static inline bool > +pci_one_device_iommu_support_va(struct rte_pci_device *dev) > +{ This is not in fast path, there is no reason it should be inline