From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id 1AADA2E41 for ; Mon, 20 Aug 2018 10:19:06 +0200 (CEST) X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Aug 2018 01:19:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,264,1531810800"; d="scan'208";a="74148047" Received: from debian.sh.intel.com (HELO debian) ([10.67.104.194]) by FMSMGA003.fm.intel.com with ESMTP; 20 Aug 2018 01:18:49 -0700 Date: Mon, 20 Aug 2018 16:18:04 +0800 From: Tiwei Bie To: Luca Boccassi Cc: dev@dpdk.org, maxime.coquelin@redhat.com, zhihong.wang@intel.com, bruce.richardson@intel.com, brian.russell@intl.att.com Message-ID: <20180820081804.GA29806@debian> References: <20180814143035.19640-1-bluca@debian.org> <20180816184750.30843-1-bluca@debian.org> <20180816184750.30843-2-bluca@debian.org> <1534445383.5764.56.camel@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1534445383.5764.56.camel@debian.org> User-Agent: Mutt/1.10.1 (2018-07-13) Subject: Re: [dpdk-dev] [PATCH 2/2] virtio: fix PCI config err handling X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 20 Aug 2018 08:19:07 -0000 On Thu, Aug 16, 2018 at 07:49:43PM +0100, Luca Boccassi wrote: > On Thu, 2018-08-16 at 19:47 +0100, Luca Boccassi wrote: > > From: Brian Russell > > > > In virtio_read_caps and vtpci_msix_detect, rte_pci_read_config > > returns > > the number of bytes read from PCI config or < 0 on error. > > If less than the expected number of bytes are read then log the > > failure and return rather than carrying on with garbage. > > > > Fixes: 6ba1f63b5ab0 ("virtio: support specification 1.0") > > > > Signed-off-by: Brian Russell > > Signed-off-by: Luca Boccassi > > --- > > v2: handle additional rte_pci_read_config incomplete reads > > > >  drivers/net/virtio/virtio_pci.c | 35 +++++++++++++++++++++-------- > > ---- > >  1 file changed, 22 insertions(+), 13 deletions(-) > > > > diff --git a/drivers/net/virtio/virtio_pci.c > > b/drivers/net/virtio/virtio_pci.c > > index 6bd22e54a6..ff6f96f361 100644 > > --- a/drivers/net/virtio/virtio_pci.c > > +++ b/drivers/net/virtio/virtio_pci.c > ... > > @@ -610,9 +613,13 @@ virtio_read_caps(struct rte_pci_device *dev, > > struct virtio_hw *hw) > >   hw->common_cfg = get_cfg_addr(dev, &cap); > >   break; > >   case VIRTIO_PCI_CAP_NOTIFY_CFG: > > - rte_pci_read_config(dev, &hw- > > >notify_off_multiplier, > > - 4, pos + sizeof(cap)); > > - hw->notify_base = get_cfg_addr(dev, &cap); > > + /* Avoid half-reads into hw */ > > + ret = rte_pci_read_config(dev, &multiplier, > > 4, > > + pos + sizeof(cap)); > > + if (ret == 4) { > > + hw->notify_off_multiplier = > > multiplier; > > + hw->notify_base = get_cfg_addr(dev, > > &cap); > > + } > >   break; > >   case VIRTIO_PCI_CAP_DEVICE_CFG: > >   hw->dev_cfg = get_cfg_addr(dev, &cap); > > Tiwei: not 100% sure what's the best way to handle a failure here, this > will avoid writing to *hw in case of errors. Let me know if this is OK. My concern is about reading the virtio capability directly. With this patch, it will give up reading other capabilities when failed to read a full virtio PCI capability structure (the returned bytes are less than the expected bytes) even though when the capability it's reading isn't a virtio vendor specific capability. I'm not quite sure whether it will bring any bad consequence. How about just reading the first two bytes first? Something like this: https://github.com/freebsd/freebsd/blob/72445a41b3ff/sys/dev/pci/pci.c#L1491-L1497 Thanks