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From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
	"Stojaczyk, Dariusz" <dariusz.stojaczyk@intel.com>,
	David Marchand <david.marchand@redhat.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v4 0/4] Fixes on IOVA mode selection
Date: Tue, 23 Jul 2019 15:29:51 +0100
Message-ID: <3e82b693-6680-ee0d-b5cb-4f2e881e6ba3@intel.com> (raw)
In-Reply-To: <751d0163-ed33-e05b-dd24-386055114384@intel.com>

On 23-Jul-19 2:56 PM, Burakov, Anatoly wrote:
> On 23-Jul-19 11:25 AM, Thomas Monjalon wrote:
>> 23/07/2019 11:57, Burakov, Anatoly:
>>> A machine without an IOMMU shouldn't have picked IOVA as VA in the first
>>> place. Perhaps this is something we could fix? I'm not sure how to
>>> detected that condition though, i don't think there's a mechanism to
>>> know that for sure. Some kernels create a "iommu" sysfs directories, but
>>> i'm not too sure if they're 1) there for older kernels we support, and
>>> 2) always there.
>> [..]
>>> On my machine, "/sys/devices/virtual/iommu" exists when IOMMU is
>>> enabled, but doesn't exist if it isn't ("/sys/class/iommu" exists in
>>> both cases, but is empty when IOMMU is disabled). Perhaps we could go
>>> off that?
>>
>> Yes, good idea.
>> We need to check how these sysfs entries are managed,
>> and how old they are by looking at Linux code history.
>>
> 
> Quick (and by no means thorough) Google reveals that IOMMU driver's 
> sysfs-related code dates back as far as kernel version 3.17:
> 
> https://elixir.bootlin.com/linux/v3.17.8/source/drivers/iommu/iommu-sysfs.c
> 
> I'm not a kernel code expert, but the code *looks* like it's creating an 
> IOMMU-related entry in sysfs. So, i take it we can be reasonably sure of 
> these entries' presence at least since v3.17 onwards? Do we support 
> kernels which don't have this code?
> 

After a short chat with Ferruh, i think we have even better way to 
determine whether IOMMU is enabled - the /sys/kernel/iommu filesystem. 
Those are created whenever it is possible for VFIO to run, even if VFIO 
driver itself is not loaded. These have been there since kernel 3.6, so 
our minimum requirements are met with this approach, i believe.

-- 
Thanks,
Anatoly

  parent reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-10 21:48 [dpdk-dev] [PATCH 0/2] " David Marchand
2019-07-10 21:48 ` [dpdk-dev] [PATCH 1/2] Revert "bus/pci: add Mellanox kernel driver type" David Marchand
2019-07-16 10:37   ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-10 21:48 ` [dpdk-dev] [PATCH 2/2] eal: fix IOVA mode selection as VA for pci drivers David Marchand
2019-07-11 14:40   ` Thomas Monjalon
2019-07-12  8:05     ` Jerin Jacob Kollanukkaran
2019-07-12 11:03   ` Burakov, Anatoly
2019-07-12 12:43     ` Thomas Monjalon
2019-07-12 12:58       ` Burakov, Anatoly
2019-07-12 13:19         ` Bruce Richardson
2019-07-15 14:26       ` Jerin Jacob Kollanukkaran
2019-07-15 15:03         ` Thomas Monjalon
2019-07-15 15:35           ` Jerin Jacob Kollanukkaran
2019-07-15 16:06             ` Thomas Monjalon
2019-07-15 16:27               ` Jerin Jacob Kollanukkaran
2019-07-16 13:46 ` [dpdk-dev] [PATCH v2 0/4] Fixes on IOVA mode selection jerinj
2019-07-16 13:46   ` [dpdk-dev] [PATCH v2 1/4] Revert "bus/pci: add Mellanox kernel driver type" jerinj
2019-07-16 13:46   ` [dpdk-dev] [PATCH v2 2/4] eal: fix IOVA mode selection as VA for pci drivers jerinj
2019-07-16 14:26     ` Burakov, Anatoly
2019-07-16 15:07       ` Jerin Jacob Kollanukkaran
2019-07-16 13:46   ` [dpdk-dev] [PATCH v2 3/4] eal: change RTE_PCI_DRV_IOVA_AS_VA flag name jerinj
2019-07-16 13:46   ` [dpdk-dev] [PATCH v2 4/4] eal: select IOVA mode as VA for default case jerinj
2019-07-16 14:33     ` Burakov, Anatoly
2019-07-17  8:33       ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-17 12:38         ` Burakov, Anatoly
2019-07-17 14:04           ` Jerin Jacob Kollanukkaran
2019-07-18  6:45   ` [dpdk-dev] [PATCH v3 0/4] Fixes on IOVA mode selection jerinj
2019-07-18  6:45     ` [dpdk-dev] [PATCH v3 1/4] Revert "bus/pci: add Mellanox kernel driver type" jerinj
2019-07-18  6:45     ` [dpdk-dev] [PATCH v3 2/4] eal: fix IOVA mode selection as VA for pci drivers jerinj
2019-07-18  6:45     ` [dpdk-dev] [PATCH v3 3/4] eal: change RTE_PCI_DRV_IOVA_AS_VA flag name jerinj
2019-07-18  6:45     ` [dpdk-dev] [PATCH v3 4/4] eal: select IOVA mode as VA for default case jerinj
2019-07-22 11:28     ` [dpdk-dev] [PATCH v3 0/4] Fixes on IOVA mode selection David Marchand
2019-07-22 12:56 ` [dpdk-dev] [PATCH v4 " David Marchand
2019-07-22 12:56   ` [dpdk-dev] [PATCH v4 1/4] Revert "bus/pci: add Mellanox kernel driver type" David Marchand
2019-07-22 12:56   ` [dpdk-dev] [PATCH v4 2/4] eal: fix IOVA mode selection as VA for PCI drivers David Marchand
2019-11-25  9:33     ` Ferruh Yigit
2019-11-25 10:22       ` Thomas Monjalon
2019-11-25 12:03         ` Ferruh Yigit
2019-11-25 12:36           ` David Marchand
2019-11-25 12:58             ` Burakov, Anatoly
2019-11-25 14:29               ` Thomas Monjalon
2019-11-25 11:07       ` Jerin Jacob
2019-07-22 12:56   ` [dpdk-dev] [PATCH v4 3/4] drivers: change IOVA as VA PCI flag name David Marchand
2019-07-22 12:56   ` [dpdk-dev] [PATCH v4 4/4] eal: select IOVA as VA mode for default case David Marchand
2019-07-22 15:53   ` [dpdk-dev] [PATCH v4 0/4] Fixes on IOVA mode selection Thomas Monjalon
2019-07-23  3:35     ` Stojaczyk, Dariusz
2019-07-23  4:18       ` Jerin Jacob Kollanukkaran
2019-07-23  4:54         ` Stojaczyk, Dariusz
2019-07-23  5:27           ` Jerin Jacob Kollanukkaran
2019-07-23  7:21             ` Thomas Monjalon
2019-07-23  9:57             ` Burakov, Anatoly
2019-07-23 10:25               ` Thomas Monjalon
2019-07-23 13:56                 ` Burakov, Anatoly
2019-07-23 14:24                   ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-23 14:29                   ` Burakov, Anatoly [this message]
2019-07-23 14:36                     ` Jerin Jacob Kollanukkaran
2019-07-23 15:47                       ` Burakov, Anatoly

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