From: "Raj, Ashok" <ashok.raj@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: yi.y.sun@intel.com,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
kevin.tian@intel.com, Ashok Raj <ashok.raj@intel.com>,
kvm@vger.kernel.org, iommu@lists.linux-foundation.org,
stefanha@gmail.com, Jason Wang <jasowang@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
jun.j.tian@intel.com,
Alex Williamson <alex.williamson@redhat.com>,
Jacon Jun Pan <jacob.jun.pan@intel.com>,
hao.wu@intel.com
Subject: Re: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs
Date: Tue, 15 Sep 2020 12:26:32 -0700 [thread overview]
Message-ID: <20200915192632.GA71024@otc-nc-03> (raw)
In-Reply-To: <20200915184510.GB1573713@nvidia.com>
On Tue, Sep 15, 2020 at 03:45:10PM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 15, 2020 at 11:11:54AM -0700, Raj, Ashok wrote:
> > > PASID applies widely to many device and needs to be introduced with a
> > > wide community agreement so all scenarios will be supportable.
> >
> > True, reading some of the earlier replies I was clearly confused as I
> > thought you were talking about mdev again. But now that you stay it, you
> > have moved past mdev and its the PASID interfaces correct?
>
> Yes, we agreed mdev for IDXD at LPC, didn't talk about PASID.
>
> > For the native user applications have just 1 PASID per
> > process. There is no need for a quota management.
>
> Yes, there is. There is a limited pool of HW PASID's. If one user fork
> bombs it can easially claim an unreasonable number from that pool as
> each process will claim a PASID. That can DOS the rest of the system.
Not sure how you had this played out.. For PASID used in ENQCMD today for
our SVM usages, we *DO* not automatically propagate or allocate new PASIDs.
The new process needs to bind to get a PASID for its own use. For threads
of same process the PASID is inherited. For forks(), we do not
auto-allocate them. Since PASID isn't a sharable resource much like how you
would not pass mmio mmap's to forked processes that cannot be shared correct?
Such as your doorbell space for e.g.
>
> If PASID DOS is a worry then it must be solved at the IOMMU level for
> all user applications that might trigger a PASID allocation. VFIO is
> not special.
Feels like you can simply avoid the PASID DOS rather than permit it to
happen.
>
> > IIUC, you are asking that part of the interface to move to a API interface
> > that potentially the new /dev/sva and VFIO could share? I think the API's
> > for PASID management themselves are generic (Jean's patchset + Jacob's
> > ioasid set management).
>
> Yes, the in kernel APIs are pretty generic now, and can be used by
> many types of drivers.
Good, so there is no new requirements here I suppose.
>
> As JasonW kicked this off, VDPA will need all this identical stuff
> too. We already know this, and I think Intel VDPA HW will need it, so
> it should concern you too :)
This is one of those things that I would disagree and commit :-)..
>
> A PASID vIOMMU solution sharable with VDPA and VFIO, based on a PASID
> control char dev (eg /dev/sva, or maybe /dev/iommu) seems like a
> reasonable starting point for discussion.
Looks like now we are getting closer to what we need. :-)
Given that PASID api's are general purpose today and any driver can use it
to take advantage. VFIO fortunately or unfortunately has the IOMMU things
abstracted. I suppose that support is also mostly built on top of the
generic iommu* api abstractions in a vendor neutral way?
I'm still lost on what is missing that vDPA can't build on top of what is
available?
Cheers,
Ashok
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next prev parent reply other threads:[~2020-09-15 19:26 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-10 10:45 [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Liu Yi L
2020-09-10 10:45 ` [PATCH v7 01/16] iommu: Report domain nesting info Liu Yi L
2020-09-11 19:38 ` Alex Williamson
2020-09-10 10:45 ` [PATCH v7 02/16] iommu/smmu: Report empty " Liu Yi L
2021-01-12 6:50 ` Vivek Gautam
2021-01-12 9:21 ` Liu, Yi L
2021-01-12 11:05 ` Vivek Gautam
2021-01-13 5:56 ` Liu, Yi L
2021-01-19 10:03 ` Auger Eric
2021-01-23 8:59 ` Liu, Yi L
2021-02-12 7:14 ` Vivek Gautam
2021-02-12 9:57 ` Auger Eric
2021-02-12 10:18 ` Vivek Kumar Gautam
2021-02-12 11:01 ` Vivek Kumar Gautam
2021-03-03 9:44 ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 03/16] vfio/type1: Report iommu nesting info to userspace Liu Yi L
2020-09-11 20:16 ` Alex Williamson
2020-09-12 8:24 ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 04/16] vfio: Add PASID allocation/free support Liu Yi L
2020-09-11 20:54 ` Alex Williamson
2020-09-15 4:03 ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 05/16] iommu/vt-d: Support setting ioasid set to domain Liu Yi L
2020-09-10 10:45 ` [PATCH v7 06/16] iommu/vt-d: Remove get_task_mm() in bind_gpasid() Liu Yi L
2020-09-10 10:45 ` [PATCH v7 07/16] vfio/type1: Add VFIO_IOMMU_PASID_REQUEST (alloc/free) Liu Yi L
2020-09-11 21:38 ` Alex Williamson
2020-09-12 6:17 ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 08/16] iommu: Pass domain to sva_unbind_gpasid() Liu Yi L
2020-09-10 10:45 ` [PATCH v7 09/16] iommu/vt-d: Check ownership for PASIDs from user-space Liu Yi L
2020-09-10 10:45 ` [PATCH v7 10/16] vfio/type1: Support binding guest page tables to PASID Liu Yi L
2020-09-11 22:03 ` Alex Williamson
2020-09-12 6:02 ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 11/16] vfio/type1: Allow invalidating first-level/stage IOMMU cache Liu Yi L
2020-09-10 10:45 ` [PATCH v7 12/16] vfio/type1: Add vSVA support for IOMMU-backed mdevs Liu Yi L
2020-09-10 10:45 ` [PATCH v7 13/16] vfio/pci: Expose PCIe PASID capability to guest Liu Yi L
2020-09-11 22:13 ` Alex Williamson
2020-09-12 7:17 ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 14/16] vfio: Document dual stage control Liu Yi L
2020-09-10 10:45 ` [PATCH v7 15/16] iommu/vt-d: Only support nesting when nesting caps are consistent across iommu units Liu Yi L
2020-09-10 10:45 ` [PATCH v7 16/16] iommu/vt-d: Support reporting nesting capability info Liu Yi L
2020-09-14 4:20 ` [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Jason Wang
2020-09-14 8:01 ` Tian, Kevin
2020-09-14 8:57 ` Jason Wang
2020-09-14 10:38 ` Tian, Kevin
2020-09-14 11:38 ` Jason Gunthorpe
2020-09-14 13:31 ` Jean-Philippe Brucker
2020-09-14 13:47 ` Jason Gunthorpe
2020-09-14 16:22 ` Raj, Ashok
2020-09-14 16:33 ` Jason Gunthorpe
2020-09-14 16:58 ` Alex Williamson
2020-09-14 17:41 ` Jason Gunthorpe
2020-09-14 18:23 ` Alex Williamson
2020-09-14 19:00 ` Jason Gunthorpe
2020-09-14 22:33 ` Alex Williamson
2020-09-15 14:29 ` Jason Gunthorpe
2020-09-16 1:19 ` Tian, Kevin
2020-09-16 8:32 ` Jean-Philippe Brucker
2020-09-16 14:51 ` Jason Gunthorpe
2020-09-16 16:20 ` Jean-Philippe Brucker
2020-09-16 16:32 ` Jason Gunthorpe
2020-09-16 16:50 ` Auger Eric
2020-09-16 14:44 ` Jason Gunthorpe
2020-09-17 6:01 ` Tian, Kevin
2020-09-14 22:44 ` Raj, Ashok
2020-09-15 11:33 ` Jason Gunthorpe
2020-09-15 18:11 ` Raj, Ashok
2020-09-15 18:45 ` Jason Gunthorpe
2020-09-15 19:26 ` Raj, Ashok [this message]
2020-09-15 23:45 ` Jason Gunthorpe
2020-09-16 2:33 ` Jason Wang
2020-09-15 22:08 ` Jacob Pan
2020-09-15 23:51 ` Jason Gunthorpe
2020-09-16 0:22 ` Jacob Pan (Jun)
2020-09-16 1:46 ` Lu Baolu
2020-09-16 15:07 ` Jason Gunthorpe
2020-09-16 16:33 ` Raj, Ashok
2020-09-16 17:01 ` Jason Gunthorpe
2020-09-16 18:21 ` Jacob Pan (Jun)
2020-09-16 18:38 ` Jason Gunthorpe
2020-09-16 23:09 ` Jacob Pan (Jun)
2020-09-17 3:53 ` Jason Wang
2020-09-17 17:31 ` Jason Gunthorpe
2020-09-17 18:17 ` Jacob Pan (Jun)
2020-09-18 3:58 ` Jason Wang
2020-09-16 2:29 ` Jason Wang
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