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From: Alex Williamson <alex.williamson@redhat.com>
To: "Liu, Yi L" <yi.l.liu@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"mtosatti@redhat.com" <mtosatti@redhat.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"bluca@debian.org" <bluca@debian.org>,
	"jerinjacobk@gmail.com" <jerinjacobk@gmail.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"cohuck@redhat.com" <cohuck@redhat.com>
Subject: Re: [dpdk-dev] [RFC PATCH 0/7] vfio/pci: SR-IOV support
Date: Wed, 5 Feb 2020 07:10:56 -0700	[thread overview]
Message-ID: <20200205071056.101ad3f2@x1.home> (raw)
In-Reply-To: <A2975661238FB949B60364EF0F2C25743A1ABFE0@SHSMSX104.ccr.corp.intel.com>

On Wed, 5 Feb 2020 07:57:21 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> Hi Alex,
> 
> Silly questions on the background:
> 
> > From: Alex Williamson <alex.williamson@redhat.com>
> > Sent: Wednesday, February 5, 2020 7:06 AM
> > Subject: [RFC PATCH 0/7] vfio/pci: SR-IOV support
> > 
> > There seems to be an ongoing desire to use userspace, vfio-based
> > drivers for both SR-IOV PF and VF devices.   
> 
> Is this series to make PF be bound-able to vfio-pci even SR-IOV is
> enabled on such PFs? If yes, is it allowed to assign PF to a VM? or
> it can only be used by userspace applications like DPDK?

No, this series does not change the behavior of vfio-pci with respect
to probing a PF where VFs are already enabled.  This is still
disallowed.  I haven't seen a use case that requires this and allowing
it tends to subvert the restrictions here.  For instance, if an
existing VF is already in use by a vfio-pci driver, the PF can
transition from a trusted host driver to an unknown userspace driver.

> > The fundamental issue
> > with this concept is that the VF is not fully independent of the PF
> > driver.  Minimally the PF driver might be able to deny service to the
> > VF, VF data paths might be dependent on the state of the PF device,
> > or the PF my have some degree of ability to inspect or manipulate the
> > VF data.  It therefore would seem irresponsible to unleash VFs onto
> > the system, managed by a user owned PF.
> > 
> > We address this in a few ways in this series.  First, we can use a bus
> > notifier and the driver_override facility to make sure VFs are bound
> > to the vfio-pci driver by default.  This should eliminate the chance
> > that a VF is accidentally bound and used by host drivers.  We don't
> > however remove the ability for a host admin to change this override.
> > 
> > The next issue we need to address is how we let userspace drivers
> > opt-in to this participation with the PF driver.  We do not want an
> > admin to be able to unwittingly assign one of these VFs to a tenant
> > that isn't working in collaboration with the PF driver.  We could use
> > IOMMU grouping, but this seems to push too far towards tightly coupled
> > PF and VF drivers.  This series introduces a "VF token", implemented
> > as a UUID, as a shared secret between PF and VF drivers.  The token
> > needs to be set by the PF driver and used as part of the device
> > matching by the VF driver.  Provisions in the code also account for
> > restarting the PF driver with active VF drivers, requiring the PF to
> > use the current token to re-gain access to the PF.  
> 
> How about the scenario in which PF driver is vfio-based userspace
> driver but VF drivers are mixed. This means not all VFs are bound
> to vfio-based userspace driver. Is it also supported here? :-)

It's allowed.  Userspace VF drivers will need to participate in the VF
token scheme, host drivers may be bound to VFs normally after removing
the default driver_override.  Thanks,

Alex


  reply	other threads:[~2020-02-05 14:11 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-04 23:05 Alex Williamson
2020-02-04 23:05 ` [dpdk-dev] [RFC PATCH 1/7] vfio: Include optional device match in vfio_device_ops callbacks Alex Williamson
2020-02-06 11:14   ` Cornelia Huck
2020-02-06 18:18     ` Alex Williamson
2020-02-07  9:33       ` Cornelia Huck
2020-02-04 23:05 ` [dpdk-dev] [RFC PATCH 2/7] vfio/pci: Implement match ops Alex Williamson
2020-02-04 23:06 ` [dpdk-dev] [RFC PATCH 3/7] vfio/pci: Introduce VF token Alex Williamson
2020-02-05  7:57   ` Liu, Yi L
2020-02-05 14:13     ` Alex Williamson
2020-02-04 23:06 ` [dpdk-dev] [RFC PATCH 4/7] vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user Alex Williamson
2020-02-04 23:06 ` [dpdk-dev] [RFC PATCH 5/7] vfio/pci: Add sriov_configure support Alex Williamson
2020-02-04 23:06 ` [dpdk-dev] [RFC PATCH 6/7] vfio/pci: Remove dev_fmt definition Alex Williamson
2020-02-06 13:45   ` Cornelia Huck
2020-02-04 23:06 ` [dpdk-dev] [RFC PATCH 7/7] vfio/pci: Cleanup .probe() exit paths Alex Williamson
2020-02-04 23:17 ` [dpdk-dev] [RFC PATCH 0/7] vfio/pci: SR-IOV support Alex Williamson
2020-02-05  7:57   ` Liu, Yi L
2020-02-05 14:18     ` Alex Williamson
2020-02-05  7:01 ` Christoph Hellwig
2020-02-05 13:58   ` Alex Williamson
2020-02-05  7:57 ` Liu, Yi L
2020-02-05 14:10   ` Alex Williamson [this message]
2020-02-11 11:18 ` Jerin Jacob
2020-02-11 13:57   ` Thomas Monjalon
2020-02-11 17:06   ` Alex Williamson
2020-02-11 18:03     ` Jerin Jacob

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