From: Lu Baolu <baolu.lu@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>, Christoph Hellwig <hch@lst.de>
Cc: baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
David Woodhouse <dwmw2@infradead.org>,
Alex Williamson <alex.williamson@redhat.com>,
Kirti Wankhede <kwankhede@nvidia.com>,
ashok.raj@intel.com, sanjay.k.kumar@intel.com,
jacob.jun.pan@intel.com, kevin.tian@intel.com,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
yi.l.liu@intel.com, yi.y.sun@intel.com, peterx@redhat.com,
tiwei.bie@intel.com, xin.zeng@intel.com,
iommu@lists.linux-foundation.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org,
Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: Re: [PATCH v8 7/9] vfio/mdev: Add iommu related member in mdev_device
Date: Wed, 7 Apr 2021 09:58:05 +0800 [thread overview]
Message-ID: <1cbe97fb-5595-8cf5-9e0c-1a2edf8c5d9a@linux.intel.com> (raw)
In-Reply-To: <20210406200030.GA425310@nvidia.com>
Hi Jason,
On 4/7/21 4:00 AM, Jason Gunthorpe wrote:
> On Mon, Mar 25, 2019 at 09:30:34AM +0800, Lu Baolu wrote:
>> A parent device might create different types of mediated
>> devices. For example, a mediated device could be created
>> by the parent device with full isolation and protection
>> provided by the IOMMU. One usage case could be found on
>> Intel platforms where a mediated device is an assignable
>> subset of a PCI, the DMA requests on behalf of it are all
>> tagged with a PASID. Since IOMMU supports PASID-granular
>> translations (scalable mode in VT-d 3.0), this mediated
>> device could be individually protected and isolated by an
>> IOMMU.
>>
>> This patch adds a new member in the struct mdev_device to
>> indicate that the mediated device represented by mdev could
>> be isolated and protected by attaching a domain to a device
>> represented by mdev->iommu_device. It also adds a helper to
>> add or set the iommu device.
>>
>> * mdev_device->iommu_device
>> - This, if set, indicates that the mediated device could
>> be fully isolated and protected by IOMMU via attaching
>> an iommu domain to this device. If empty, it indicates
>> using vendor defined isolation, hence bypass IOMMU.
>>
>> * mdev_set/get_iommu_device(dev, iommu_device)
>> - Set or get the iommu device which represents this mdev
>> in IOMMU's device scope. Drivers don't need to set the
>> iommu device if it uses vendor defined isolation.
>>
>> Cc: Ashok Raj <ashok.raj@intel.com>
>> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
>> Cc: Kevin Tian <kevin.tian@intel.com>
>> Cc: Liu Yi L <yi.l.liu@intel.com>
>> Suggested-by: Kevin Tian <kevin.tian@intel.com>
>> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
>> ---
>> drivers/vfio/mdev/mdev_core.c | 18 ++++++++++++++++++
>> drivers/vfio/mdev/mdev_private.h | 1 +
>> include/linux/mdev.h | 14 ++++++++++++++
>> 3 files changed, 33 insertions(+)
>>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index b96fedc77ee5..1b6435529166 100644
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -390,6 +390,24 @@ int mdev_device_remove(struct device *dev, bool force_remove)
>> return 0;
>> }
>>
>> +int mdev_set_iommu_device(struct device *dev, struct device *iommu_device)
>> +{
>> + struct mdev_device *mdev = to_mdev_device(dev);
>> +
>> + mdev->iommu_device = iommu_device;
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL(mdev_set_iommu_device);
>
> I was looking at these functions when touching the mdev stuff and I
> have some concerns.
>
> 1) Please don't merge dead code. It is a year later and there is still
> no in-tree user for any of this. This is not our process. Even
> worse it was exported so it looks like this dead code is supporting
> out of tree modules.
>
> 2) Why is this like this? Every struct device already has a connection
> to the iommu layer and every mdev has a struct device all its own.
>
> Why did we need to add special 'if (mdev)' stuff all over the
> place? This smells like the same abuse Thomas
> and I pointed out for the interrupt domains.
I've ever tried to implement a bus iommu_ops for mdev devices.
https://lore.kernel.org/lkml/20201030045809.957927-1-baolu.lu@linux.intel.com/
Any comments?
Best regards,
baolu
>
> After my next series the mdev drivers will have direct access to
> the vfio_device. So an alternative to using the struct device, or
> adding 'if mdev' is to add an API to the vfio_device world to
> inject what iommu configuration is needed from that direction
> instead of trying to discover it from a struct device.
>
> 3) The vfio_bus_is_mdev() and related symbol_get() nonsense in
> drivers/vfio/vfio_iommu_type1.c has to go, for the same reasons
> it was not acceptable to do this for the interrupt side either.
>
> 4) It seems pretty clear to me this will be heavily impacted by the
> /dev/ioasid discussion. Please consider removing the dead code now.
>
> Basically, please fix this before trying to get idxd mdev merged as
> the first user.
>
> Jason
>
next prev parent reply other threads:[~2021-04-07 2:07 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 1:30 [PATCH v8 0/9] vfio/mdev: IOMMU aware mediated device Lu Baolu
2019-03-25 1:30 ` [PATCH v8 2/9] iommu/vt-d: Make intel_iommu_enable_pasid() more generic Lu Baolu
2019-03-25 1:30 ` [PATCH v8 3/9] iommu/vt-d: Add per-device IOMMU feature ops entries Lu Baolu
2019-03-25 1:30 ` [PATCH v8 4/9] iommu/vt-d: Move common code out of iommu_attch_device() Lu Baolu
2019-03-25 1:30 ` [PATCH v8 5/9] iommu/vt-d: Aux-domain specific domain attach/detach Lu Baolu
[not found] ` <20190325013036.18400-1-baolu.lu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2019-03-25 1:30 ` [PATCH v8 1/9] iommu: Add APIs for multiple domains per device Lu Baolu
2019-03-25 1:30 ` [PATCH v8 6/9] iommu/vt-d: Return ID associated with an auxiliary domain Lu Baolu
2019-03-25 1:30 ` [PATCH v8 7/9] vfio/mdev: Add iommu related member in mdev_device Lu Baolu
2019-03-26 9:32 ` Kirti Wankhede
2019-03-27 14:17 ` Parav Pandit
[not found] ` <VI1PR0501MB2271172964AFA3CDD6F1B02CD1580-o1MPJYiShEx8vvm6e75m2MDSnupUy6xnnBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>
2019-03-27 18:16 ` Alex Williamson
2019-03-26 17:42 ` Alex Williamson
2021-04-06 20:00 ` Jason Gunthorpe
2021-04-07 1:58 ` Lu Baolu [this message]
2021-04-07 11:34 ` Jason Gunthorpe
2021-05-11 6:56 ` Lu Baolu
2021-05-11 17:37 ` Jason Gunthorpe
2021-05-12 7:46 ` Tian, Kevin
2021-05-17 14:03 ` Jason Gunthorpe
2019-03-25 1:30 ` [PATCH v8 8/9] vfio/type1: Add domain at(de)taching group helpers Lu Baolu
[not found] ` <20190325013036.18400-9-baolu.lu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2019-03-26 17:42 ` Alex Williamson
2019-03-25 1:30 ` [PATCH v8 9/9] vfio/type1: Handle different mdev isolation type Lu Baolu
2019-03-26 9:33 ` Kirti Wankhede
2019-03-26 17:42 ` Alex Williamson
2019-04-11 15:19 ` [PATCH v8 0/9] vfio/mdev: IOMMU aware mediated device Joerg Roedel
2019-04-12 1:36 ` Lu Baolu
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