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From: Jason Gunthorpe <jgg@nvidia.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>, "hch@lst.de" <hch@lst.de>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"jean-philippe@linaro.org" <jean-philippe@linaro.org>,
	"parav@mellanox.com" <parav@mellanox.com>,
	"lkml@metux.net" <lkml@metux.net>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"lushenming@huawei.com" <lushenming@huawei.com>,
	"eric.auger@redhat.com" <eric.auger@redhat.com>,
	"corbet@lwn.net" <corbet@lwn.net>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	"yi.l.liu@linux.intel.com" <yi.l.liu@linux.intel.com>,
	"Tian, Jun J" <jun.j.tian@intel.com>,
	"Wu, Hao" <hao.wu@intel.com>,
	"Jiang, Dave" <dave.jiang@intel.com>,
	"jacob.jun.pan@linux.intel.com" <jacob.jun.pan@linux.intel.com>,
	"kwankhede@nvidia.com" <kwankhede@nvidia.com>,
	"robin.murphy@arm.com" <robin.murphy@arm.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"dwmw2@infradead.org" <dwmw2@infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
	"david@gibson.dropbear.id.au" <david@gibson.dropbear.id.au>,
	"nicolinc@nvidia.com" <nicolinc@nvidia.com>
Subject: Re: [RFC 10/20] iommu/iommufd: Add IOMMU_DEVICE_GET_INFO
Date: Mon, 25 Oct 2021 20:34:59 -0300	[thread overview]
Message-ID: <20211025233459.GM2744544@nvidia.com> (raw)
In-Reply-To: <BN9PR11MB5433482C3754A8A383C3B6298C809@BN9PR11MB5433.namprd11.prod.outlook.com>

On Fri, Oct 22, 2021 at 03:08:06AM +0000, Tian, Kevin wrote:

> > I have no idea what security model makes sense for wbinvd, that is the
> > major question you have to answer.
> 
> wbinvd flushes the entire cache in local cpu. It's more a performance
> isolation problem but nothing can prevent it once the user is allowed
> to call this ioctl. This is the main reason why wbinvd is a privileged 
> instruction and is emulated by kvm as a nop unless an assigned device
> has no-snoop requirement. alternatively the user may call clflush
> which is unprivileged and can invalidate a specific cache line, though 
> not efficient for flushing a big buffer.
>
> One tricky thing is that the process might be scheduled to different 
> cpus between writing buffers and calling wbinvd ioctl. Since wbvind 
> only has local behavior, it requires the ioctl to call wbinvd on all
> cpus that this process has previously been scheduled on.

That is such a hassle, you may want to re-open this with the kvm
people as it seems ARM also has different behavior between VM and
process here.

The ideal is already not being met, so maybe we can keep special
casing cache ops?

> Is there any concern if iommufd also follows the same mechanism?
> Currently looks preempt notifier is only  used by kvm. Not sure whether
> there is strong criteria around using it. and this local behavior may
> not apply to all platforms (then better hidden behind arch callback?)

I don't have any desire to see a performance cost to implement an
ioctl that nothing will ever call just to satisify a idealized target
from the kvm folks..

Jason

  reply	other threads:[~2021-10-25 23:35 UTC|newest]

Thread overview: 274+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-19  6:38 [RFC 00/20] Introduce /dev/iommu for userspace I/O address space management Liu Yi L
2021-09-19  6:38 ` [RFC 01/20] iommu/iommufd: Add /dev/iommu core Liu Yi L
2021-09-21 15:41   ` Jason Gunthorpe
2021-09-22  1:51     ` Tian, Kevin
2021-09-22 12:40       ` Jason Gunthorpe
2021-09-22 13:59         ` Tian, Kevin
2021-09-22 14:10           ` Jason Gunthorpe
2021-10-15  9:18     ` Liu, Yi L
2021-10-15 11:18       ` Jason Gunthorpe
2021-10-15 11:29         ` Liu, Yi L
2021-10-19 16:57         ` Jacob Pan
2021-10-19 16:57           ` Jason Gunthorpe
2021-10-19 17:11             ` Jacob Pan
2021-10-19 17:12               ` Jason Gunthorpe
2021-09-19  6:38 ` [RFC 02/20] vfio: Add device class for /dev/vfio/devices Liu Yi L
2021-09-21 15:57   ` Jason Gunthorpe
2021-09-21 23:56     ` Tian, Kevin
2021-09-22  0:55       ` Jason Gunthorpe
2021-09-22  1:07         ` Tian, Kevin
2021-09-22 12:31           ` Jason Gunthorpe
2021-09-22  3:22         ` Tian, Kevin
2021-09-22 12:50           ` Jason Gunthorpe
2021-09-22 14:09             ` Tian, Kevin
2021-09-21 19:56   ` Alex Williamson
2021-09-22  0:56     ` Tian, Kevin
2021-09-29  2:08   ` David Gibson
2021-09-29 19:05     ` Alex Williamson
2021-09-30  2:43       ` David Gibson
2021-10-20 12:39     ` Liu, Yi L
2021-09-19  6:38 ` [RFC 03/20] vfio: Add vfio_[un]register_device() Liu Yi L
2021-09-21 16:01   ` Jason Gunthorpe
2021-09-21 23:10     ` Tian, Kevin
2021-09-22  0:53       ` Jason Gunthorpe
2021-09-22  0:59         ` Tian, Kevin
2021-09-22  9:23         ` Tian, Kevin
2021-09-22 12:22           ` Jason Gunthorpe
2021-09-22 13:44             ` Tian, Kevin
2021-09-22 20:10             ` Alex Williamson
2021-09-22 22:34               ` Tian, Kevin
2021-09-22 22:45                 ` Alex Williamson
2021-09-22 23:45                   ` Tian, Kevin
2021-09-22 23:52                     ` Jason Gunthorpe
2021-09-23  0:38                       ` Tian, Kevin
2021-09-22 23:56               ` Jason Gunthorpe
2021-09-22  0:54     ` Tian, Kevin
2021-09-22  1:00       ` Jason Gunthorpe
2021-09-22  1:02         ` Tian, Kevin
2021-09-23  7:25         ` Eric Auger
2021-09-23 11:44           ` Jason Gunthorpe
2021-09-29  2:46         ` david
2021-09-29 12:22           ` Jason Gunthorpe
2021-09-30  2:48             ` david
2021-09-29  2:43   ` David Gibson
2021-09-29  3:40     ` Tian, Kevin
2021-09-29  5:30     ` Tian, Kevin
2021-09-29  7:08       ` Cornelia Huck
2021-09-29 12:15         ` Jason Gunthorpe
2021-09-19  6:38 ` [RFC 04/20] iommu: Add iommu_device_get_info interface Liu Yi L
2021-09-21 16:19   ` Jason Gunthorpe
2021-09-22  2:31     ` Lu Baolu
2021-09-22  5:07       ` Christoph Hellwig
2021-09-29  2:52   ` David Gibson
2021-09-29  9:25     ` Lu Baolu
2021-09-29  9:29       ` Lu Baolu
2021-09-19  6:38 ` [RFC 05/20] vfio/pci: Register device to /dev/vfio/devices Liu Yi L
2021-09-21 16:40   ` Jason Gunthorpe
2021-09-21 21:09     ` Alex Williamson
2021-09-21 21:58       ` Jason Gunthorpe
2021-09-22  1:24         ` Tian, Kevin
2021-09-22  1:19       ` Tian, Kevin
2021-09-22 21:17         ` Alex Williamson
2021-09-22 23:49           ` Tian, Kevin
2021-09-19  6:38 ` [RFC 06/20] iommu: Add iommu_device_init[exit]_user_dma interfaces Liu Yi L
2021-09-21 17:09   ` Jason Gunthorpe
2021-09-22  1:47     ` Tian, Kevin
2021-09-22 12:39       ` Jason Gunthorpe
2021-09-22 13:56         ` Tian, Kevin
2021-09-27  9:42         ` Tian, Kevin
2021-09-27 11:34           ` Lu Baolu
2021-09-27 13:08             ` Tian, Kevin
2021-09-27 11:53           ` Jason Gunthorpe
2021-09-27 13:00             ` Tian, Kevin
2021-09-27 13:09               ` Jason Gunthorpe
2021-09-27 13:32                 ` Tian, Kevin
2021-09-27 14:39                   ` Jason Gunthorpe
2021-09-28  7:13                     ` Tian, Kevin
2021-09-28 11:54                       ` Jason Gunthorpe
2021-09-28 23:59                         ` Tian, Kevin
2021-09-27 19:19                   ` Alex Williamson
2021-09-28  7:43                     ` Tian, Kevin
2021-09-28 16:26                       ` Alex Williamson
2021-09-27 15:09           ` Jason Gunthorpe
2021-09-28  7:30             ` Tian, Kevin
2021-09-28 11:57               ` Jason Gunthorpe
2021-09-28 13:35                 ` Lu Baolu
2021-09-28 14:07                   ` Jason Gunthorpe
2021-09-29  0:38                     ` Tian, Kevin
2021-09-29 12:59                       ` Jason Gunthorpe
2021-10-15  1:29                         ` Tian, Kevin
2021-10-15 11:09                           ` Jason Gunthorpe
2021-10-18  1:52                             ` Tian, Kevin
2021-09-29  2:22                     ` Lu Baolu
2021-09-29  2:29                       ` Tian, Kevin
2021-09-29  2:38                         ` Lu Baolu
2021-09-29  4:55   ` David Gibson
2021-09-29  5:38     ` Tian, Kevin
2021-09-29  6:35       ` David Gibson
2021-09-29  7:31         ` Tian, Kevin
2021-09-30  3:05           ` David Gibson
2021-09-29 12:57         ` Jason Gunthorpe
2021-09-30  3:09           ` David Gibson
2021-09-30 22:28             ` Jason Gunthorpe
2021-10-01  3:54               ` David Gibson
2021-09-19  6:38 ` [RFC 07/20] iommu/iommufd: Add iommufd_[un]bind_device() Liu Yi L
2021-09-21 17:14   ` Jason Gunthorpe
2021-10-15  9:21     ` Liu, Yi L
2021-09-29  5:25   ` David Gibson
2021-09-29 12:24     ` Jason Gunthorpe
2021-09-30  3:10       ` David Gibson
2021-10-01 12:43         ` Jason Gunthorpe
2021-10-07  1:23           ` David Gibson
2021-10-07 11:35             ` Jason Gunthorpe
2021-10-11  3:24               ` David Gibson
2021-09-19  6:38 ` [RFC 08/20] vfio/pci: Add VFIO_DEVICE_BIND_IOMMUFD Liu Yi L
2021-09-21 17:29   ` Jason Gunthorpe
2021-09-22 21:01     ` Alex Williamson
2021-09-22 23:01       ` Jason Gunthorpe
2021-09-29  6:00   ` David Gibson
2021-09-29  6:41     ` Tian, Kevin
2021-09-29 12:28       ` Jason Gunthorpe
2021-09-29 22:34         ` Tian, Kevin
2021-09-30  3:12       ` David Gibson
2021-09-19  6:38 ` [RFC 09/20] iommu: Add page size and address width attributes Liu Yi L
2021-09-22 13:42   ` Eric Auger
2021-09-22 14:19     ` Tian, Kevin
2021-09-19  6:38 ` [RFC 10/20] iommu/iommufd: Add IOMMU_DEVICE_GET_INFO Liu Yi L
2021-09-21 17:40   ` Jason Gunthorpe
2021-09-22  3:30     ` Tian, Kevin
2021-09-22 12:41       ` Jason Gunthorpe
2021-09-29  6:18         ` david
2021-09-22 21:24   ` Alex Williamson
2021-09-22 23:49     ` Jason Gunthorpe
2021-09-23  3:10       ` Tian, Kevin
2021-09-23 10:15         ` Jean-Philippe Brucker
2021-09-23 11:27           ` Jason Gunthorpe
2021-09-23 12:05             ` Tian, Kevin
2021-09-23 12:22               ` Jason Gunthorpe
2021-09-29  8:48                 ` Tian, Kevin
2021-09-29 12:36                   ` Jason Gunthorpe
2021-09-30  8:30                     ` Tian, Kevin
2021-09-30 10:33                       ` Jean-Philippe Brucker
2021-09-30 22:04                         ` Jason Gunthorpe
2021-10-01  3:28                           ` hch
2021-10-14  8:13                             ` Tian, Kevin
2021-10-14  8:22                               ` hch
2021-10-14  8:29                                 ` Tian, Kevin
2021-10-14  8:01                         ` Tian, Kevin
2021-10-14  9:16                           ` Jean-Philippe Brucker
2021-09-30  8:49                 ` Tian, Kevin
2021-09-30 13:43                   ` Lu Baolu
2021-10-01  3:24                     ` hch
2021-09-30 22:08                   ` Jason Gunthorpe
2021-09-23 11:36         ` Jason Gunthorpe
     [not found]       ` <BN9PR11MB5433409DF766AAEF1BB2CF258CA39@BN9PR11MB5433.namprd11.prod.outlook.com>
2021-09-23  3:38         ` Tian, Kevin
2021-09-23 11:42           ` Jason Gunthorpe
2021-09-30  9:35             ` Tian, Kevin
2021-09-30 22:23               ` Jason Gunthorpe
2021-10-01  3:30                 ` hch
2021-10-14  9:11                 ` Tian, Kevin
2021-10-14 15:42                   ` Jason Gunthorpe
2021-10-15  1:01                     ` Tian, Kevin
     [not found]                     ` <BN9PR11MB543327BB6D58AEF91AD2C9D18CB99@BN9PR11MB5433.namprd11.prod.outlook.com>
2021-10-21  2:26                       ` Tian, Kevin
2021-10-21 14:58                         ` Jean-Philippe Brucker
2021-10-21 23:22                           ` Jason Gunthorpe
2021-10-22  7:49                             ` Jean-Philippe Brucker
2021-10-25 16:51                               ` Jason Gunthorpe
2021-10-21 23:30                         ` Jason Gunthorpe
2021-10-22  3:08                           ` Tian, Kevin
2021-10-25 23:34                             ` Jason Gunthorpe [this message]
2021-10-27  1:42                               ` Tian, Kevin
2021-10-28  2:07                               ` Tian, Kevin
2021-10-29 13:55                                 ` Jason Gunthorpe
2021-09-29  6:23   ` David Gibson
2021-09-19  6:38 ` [RFC 11/20] iommu/iommufd: Add IOMMU_IOASID_ALLOC/FREE Liu Yi L
2021-09-21 17:44   ` Jason Gunthorpe
2021-09-22  3:40     ` Tian, Kevin
2021-09-22 14:09       ` Jason Gunthorpe
2021-09-23  9:14         ` Tian, Kevin
2021-09-23 12:06           ` Jason Gunthorpe
2021-09-23 12:22             ` Tian, Kevin
2021-09-23 12:31               ` Jason Gunthorpe
2021-09-23 12:45                 ` Tian, Kevin
2021-09-23 13:01                   ` Jason Gunthorpe
2021-09-23 13:20                     ` Tian, Kevin
2021-09-23 13:30                       ` Jason Gunthorpe
2021-09-23 13:41                         ` Tian, Kevin
2021-10-01  6:30               ` david
2021-10-01  6:26           ` david
2021-10-01  6:19         ` david
2021-10-01 12:25           ` Jason Gunthorpe
2021-10-02  4:21             ` david
2021-10-02 12:25               ` Jason Gunthorpe
2021-10-11  5:37                 ` david
2021-10-11 17:17                   ` Jason Gunthorpe
2021-10-14  4:33                     ` david
2021-10-14 15:06                       ` Jason Gunthorpe
2021-10-18  3:40                         ` david
2021-10-01  6:15       ` david
2021-09-22 12:51     ` Liu, Yi L
2021-09-22 13:32       ` Jason Gunthorpe
2021-09-23  6:26         ` Liu, Yi L
2021-10-01  6:13     ` David Gibson
2021-10-01 12:22       ` Jason Gunthorpe
2021-10-11  6:02         ` David Gibson
2021-10-11  8:49           ` Jean-Philippe Brucker
2021-10-11 23:38             ` Jason Gunthorpe
2021-10-12  8:33               ` Jean-Philippe Brucker
2021-10-13  7:14                 ` Tian, Kevin
2021-10-13  7:07             ` Tian, Kevin
2021-10-14  4:38             ` David Gibson
2021-10-11 18:49           ` Jason Gunthorpe
2021-10-14  4:53             ` David Gibson
2021-10-14 14:52               ` Jason Gunthorpe
2021-10-18  3:50                 ` David Gibson
2021-10-18 17:42                   ` Jason Gunthorpe
2021-09-22 13:45   ` Jean-Philippe Brucker
2021-09-29 10:47     ` Liu, Yi L
2021-10-01  6:11   ` David Gibson
2021-10-13  7:00     ` Tian, Kevin
2021-10-14  5:00       ` David Gibson
2021-10-14  6:53         ` Tian, Kevin
2021-10-25  5:05           ` David Gibson
2021-10-27  2:32             ` Tian, Kevin
2021-09-19  6:38 ` [RFC 12/20] iommu/iommufd: Add IOMMU_CHECK_EXTENSION Liu Yi L
2021-09-21 17:47   ` Jason Gunthorpe
2021-09-22  3:41     ` Tian, Kevin
2021-09-22 12:55       ` Jason Gunthorpe
2021-09-22 14:13         ` Tian, Kevin
2021-09-19  6:38 ` [RFC 13/20] iommu: Extend iommu_at[de]tach_device() for multiple devices group Liu Yi L
2021-10-14  5:24   ` David Gibson
2021-10-14  7:06     ` Tian, Kevin
2021-10-18  3:57       ` David Gibson
2021-10-18 16:32         ` Jason Gunthorpe
2021-10-25  5:14           ` David Gibson
2021-10-25 12:14             ` Jason Gunthorpe
2021-10-25 13:16               ` David Gibson
2021-10-25 23:36                 ` Jason Gunthorpe
2021-10-26  9:23                   ` David Gibson
2021-09-19  6:38 ` [RFC 14/20] iommu/iommufd: Add iommufd_device_[de]attach_ioasid() Liu Yi L
2021-09-21 18:02   ` Jason Gunthorpe
2021-09-22  3:53     ` Tian, Kevin
2021-09-22 12:57       ` Jason Gunthorpe
2021-09-22 14:16         ` Tian, Kevin
2021-09-19  6:38 ` [RFC 15/20] vfio/pci: Add VFIO_DEVICE_[DE]ATTACH_IOASID Liu Yi L
2021-09-21 18:04   ` Jason Gunthorpe
2021-09-22  3:56     ` Tian, Kevin
2021-09-22 12:58       ` Jason Gunthorpe
2021-09-22 14:17         ` Tian, Kevin
2021-09-19  6:38 ` [RFC 16/20] vfio/type1: Export symbols for dma [un]map code sharing Liu Yi L
2021-09-21 18:14   ` Jason Gunthorpe
2021-09-22  3:57     ` Tian, Kevin
2021-09-19  6:38 ` [RFC 17/20] iommu/iommufd: Report iova range to userspace Liu Yi L
2021-09-22 14:49   ` Jean-Philippe Brucker
2021-09-29 10:44     ` Liu, Yi L
2021-09-29 12:07       ` Jean-Philippe Brucker
2021-09-29 12:31         ` Jason Gunthorpe
2021-09-19  6:38 ` [RFC 18/20] iommu/iommufd: Add IOMMU_[UN]MAP_DMA on IOASID Liu Yi L
2021-09-19  6:38 ` [RFC 19/20] iommu/vt-d: Implement device_info iommu_ops callback Liu Yi L
2021-09-19  6:38 ` [RFC 20/20] Doc: Add documentation for /dev/iommu Liu Yi L
2021-10-29  0:15   ` David Gibson
2021-10-29 12:44     ` Jason Gunthorpe
2021-09-19  6:45 ` [RFC 00/20] Introduce /dev/iommu for userspace I/O address space management Liu, Yi L
2021-09-21 13:45 ` Jason Gunthorpe
2021-09-22  3:25   ` Liu, Yi L

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