Message-ID: <1434644277.3700.41.camel@redhat.com>
Date:	Thu, 18 Jun 2015 10:17:57 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Baptiste Reynal <b.reynal@...tualopensystems.com>
Cc:	Eric Auger <eric.auger@...aro.org>, eric.auger@...com,
	"moderated list:ARM SMMU DRIVER" 
	<linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>, patches@...aro.org,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Christian Pinto <c.pinto@...tualopensystems.com>,
	Daniel Raho <s.raho@...tualopensystems.com>
Subject: Re: [PATCH v4 0/4] VFIO platform reset

On Thu, 2015-06-18 at 17:23 +0200, Baptiste Reynal wrote:
> Hello everyone,
> 
> I tested and reviewed the patches, everything's fine for me.

Hi Baptiste,

Would you like to provide a Sign-off/Ack/Review tag for the series then?

> I agree to be maintainer of vfio platform drivers, though I don't
> think the volume of patches about VFIO will justify a new mailing
> list.

Ok, I'll officially post the patch for MAINTAINERS then.  Until someone
complains, we'll continue to use the kvm list.  Thanks,

Alex

> On Thu, Jun 18, 2015 at 12:31 AM, Alex Williamson
> <alex.williamson@...hat.com> wrote:
> > On Mon, 2015-06-15 at 11:09 +0200, Eric Auger wrote:
> >> In situations where the userspace driver is stopped abnormally and the
> >> VFIO platform device is released, the assigned HW device currently is
> >> left running. As a consequence the HW device might continue issuing IRQs
> >> and performing DMA accesses.
> >>
> >> On release, no physical IRQ handler is setup anymore. Also the DMA buffers
> >> are unmapped leading to IOMMU aborts. So there is no serious consequence.
> >>
> >> However when assigning that HW device again to another userspace driver,
> >> this latter might face some unexpected IRQs and DMA accesses, which are
> >> the result of the previous assignment.
> >>
> >> In virtualization use-case, a VM newly granted with that HW device may be
> >> impacted by the assignment of that device to a previous VM:
> >> - IRQs may be injected very early when booting the new guest, even before
> >>   the guest driver has initialized leading to possible driver state
> >>   inconsistency.
> >> - DMA accesses may hit the newly mapped VM address space at addresses that
> >>   may jeopardize the integrity of the newly installed VM.
> >>
> >> Obviously the criticity depends on the assigned HW device.
> >>
> >> As opposed to PCI, there is no standard mechanism to reset the platform
> >> device.
> >>
> >> This series proposes to implement device specific reset functions in
> >> separate in-kernel vfio reset modules. The vfio-platform driver holds
> >> a whitelist of implemented triplets (compat string, module name,
> >> reset function name). When the vfio-platform driver is probed it identifies
> >> the fellow reset module/function matching the compat string of the
> >> device, if any, and forces the load of this reset module.
> >>
> >> A first reset module is provided: the vfio-platform-calxedaxgmac
> >> module which implements a basic reset for the Calxeda xgmac.
> >>
> >> The series can be found at
> >> https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.1-rc8-reset-v4
> >>
> >> History:
> >> v3 -> v4:
> >> - fix the commit message of "VFIO: platform: add reset struct and lookup table"
> >
> > Baptiste,
> >
> > Any comments?  Should we also add something like this to MAINTAINERS
> > before we go much further?
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index d8afd29..c6bf7f6 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -10545,6 +10545,12 @@ F:     drivers/vfio/
> >  F:     include/linux/vfio.h
> >  F:     include/uapi/linux/vfio.h
> >
> > +VFIO PLATFORM DRIVER
> > +M:     Baptiste Reynal <b.reynal@...tualopensystems.com>
> > +L:     kvm@...r.kernel.org
> > +S:     Maintained
> > +F:     drivers/vfio/platform/
> > +
> >  VIDEOBUF2 FRAMEWORK
> >  M:     Pawel Osciak <pawel@...iak.com>
> >  M:     Marek Szyprowski <m.szyprowski@...sung.com>
> >
> > I'm not sure what you want to be the primary list, maybe it's time to
> > ask for a vfio list.  Thanks,
> > Alex
> >
> >>
> >> v2 -> v3:
> >> - remove void module_init/exit functions in calxeda reset module
> >> - remove enum vfio_platform_reset_type
> >> - for reset lookup, use ARRAY_SIZE
> >> - in reset put use symbol_put_addr
> >>
> >> v1 -> v2:
> >> - much simplified compared to v1 although principle of external modules is
> >>   kept: removed mechanism of dynamic registration of reset functions
> >> - list is replaced by whitelist lookup table
> >> - name of the reset function also stored in the lookup table
> >> - autoload of reset modules
> >>
> >> RFC -> PATCH v1:
> >> - solution now based on a lookup list instead of specialized driver
> >>
> >>
> >> Eric Auger (4):
> >>   VFIO: platform: add reset struct and lookup table
> >>   VFIO: platform: add reset callback
> >>   VFIO: platform: populate the reset function on probe
> >>   VFIO: platform: Calxeda xgmac reset module
> >>
> >>  drivers/vfio/platform/Kconfig                      |  2 +
> >>  drivers/vfio/platform/Makefile                     |  2 +
> >>  drivers/vfio/platform/reset/Kconfig                |  7 ++
> >>  drivers/vfio/platform/reset/Makefile               |  5 ++
> >>  .../platform/reset/vfio_platform_calxedaxgmac.c    | 86 ++++++++++++++++++++++
> >>  drivers/vfio/platform/vfio_platform_common.c       | 60 ++++++++++++++-
> >>  drivers/vfio/platform/vfio_platform_private.h      |  7 ++
> >>  7 files changed, 166 insertions(+), 3 deletions(-)
> >>  create mode 100644 drivers/vfio/platform/reset/Kconfig
> >>  create mode 100644 drivers/vfio/platform/reset/Makefile
> >>  create mode 100644 drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c
> >>
> >
> >
> >



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