From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v2] eal/bus: use RTE_IOVA_PA only if phys addresses are available Date: Mon, 29 Oct 2018 00:11:20 +0100 Message-ID: <2118758.mfmA9bi2Cz@xps> References: <20180907154703.83316-1-dariusz.stojaczyk@intel.com> <20180907155843.96465-1-dariusz.stojaczyk@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org, Santosh Shukla , Hemant Agrawal , Jerin Jacob , Maxime Coquelin , Chas Williams , alejandro.lucero@netronome.com, arybchenko@solarflare.com, ferruh.yigit@intel.com, bruce.richardson@intel.com To: "Burakov, Anatoly" , Darek Stojaczyk Return-path: Received: from out3-smtp.messagingengine.com (out3-smtp.messagingengine.com [66.111.4.27]) by dpdk.org (Postfix) with ESMTP id 3DE0F4D3A for ; Mon, 29 Oct 2018 00:11:18 +0100 (CET) In-Reply-To: List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 17/09/2018 12:33, Burakov, Anatoly: > On 07-Sep-18 4:58 PM, Darek Stojaczyk wrote: > > When neither RTE_IOVA_VA nor RTE_IOVA_PA was explicitly > > requested, DPDK would currently fallback to the default > > RTE_IOVA_PA mode and possibly encounter a failure later > > on if running as a non-priviledged user. Attempting to > > use RTE_IOVA_VA if no phys addresses are available may > > help in this case. > > > > Signed-off-by: Darek Stojaczyk > > --- > > Changes since v1: > > * added a missing rte_memory.h include > > > > lib/librte_eal/common/eal_common_bus.c | 19 +++++++++++++++---- > > 1 file changed, 15 insertions(+), 4 deletions(-) > > > > diff --git a/lib/librte_eal/common/eal_common_bus.c b/lib/librte_eal/common/eal_common_bus.c > > index 0943851cc..68c581b8a 100644 > > --- a/lib/librte_eal/common/eal_common_bus.c > > +++ b/lib/librte_eal/common/eal_common_bus.c > > @@ -37,6 +37,7 @@ > > #include > > #include > > #include > > +#include > > > > #include "eal_private.h" > > > > @@ -236,9 +237,19 @@ rte_bus_get_iommu_class(void) > > mode |= bus->get_iommu_class(); > > } > > > > - if (mode != RTE_IOVA_VA) { > > - /* Use default IOVA mode */ > > - mode = RTE_IOVA_PA; > > + if (mode == RTE_IOVA_VA) > > + return RTE_IOVA_VA; > > + > > + if (mode & RTE_IOVA_PA) { > > + /* Not all buses support RTE_IOVA_VA, fallback to RTE_IOVA_PA */ > > + return RTE_IOVA_PA; > > + } > > + > > + if (rte_eal_using_phys_addrs()) { > > + /* Default to RTE_IOVA_PA only if it's supported */ > > + return RTE_IOVA_PA; > > } > > - return mode; > > + > > + /* Since RTE_IOVA_PA is unsupported, fallback to RTE_IOVA_VA */ > > + return RTE_IOVA_VA; > > } > > > > This is a good change, however I think that this is too pessimistic. If > i don't have any devices that explictly require IOVA_PA, i should be > running in IOVA_VA mode. > > This of course doesn't take hotplug into account, so a command-line > switch to force one or the other should also be available. > > For example, at startup, i might have devices bound to VFIO, so IOVA_VA > mode is picked. However, even though at a time of startup none of the > devices require physical addresses, i also know that i might later > hotplug a device that requires IOVA_PA (leaving the question of hotplug > brokenness aside for now...) - currently, this scenario will not work, > as i will be forced to use IOVA_VA mode unless i happen to have a > IOVA_PA device available at startup. > > Similarly, if i'm running DPDK as root but am only using virtual devices > like pcap, i should be able to force DPDK into using VA addresses [*], > yet currently i will be forced to use IOVA_PA if i don't *also* have a > few devices bound exclusively to VFIO. > > [*] Do we have vdev devices that require IOVA_PA? I can't think of any... If running as root, what is the benefit of using virtual addresses?