Re: [PATCHv7 10/26] vfio: platform: probe to devices on the platform bus

From: Antonios Motakis <a.motakis@virtualopensystems.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: kvm-arm <kvmarm@lists.cs.columbia.edu>,
	Linux IOMMU <iommu@lists.linux-foundation.org>,
	VirtualOpenSystems Technical Team <tech@virtualopensystems.com>,
	KVM devel mailing list <kvm@vger.kernel.org>,
	Christoffer Dall <christoffer.dall@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	Kim Phillips <kim.phillips@freescale.com>,
	Eric Auger <eric.auger@linaro.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	open list <linux-kernel@vger.kernel.org>,
	"open list:ABI/API" <linux-api@vger.kernel.org>
Subject: Re: [PATCHv7 10/26] vfio: platform: probe to devices on the platform bus
Date: Mon, 29 Sep 2014 12:21:02 +0200	[thread overview]
Message-ID: <CAG8rG2xNN9=47NEZ2vMVQy3eSvDN+_DMzqHiELQQfTyPYiYwVA@mail.gmail.com> (raw)
In-Reply-To: <1411762736.7360.42.camel@ul30vt.home>

On Fri, Sep 26, 2014 at 10:18 PM, Alex Williamson
<alex.williamson@redhat.com> wrote:
> On Fri, 2014-09-26 at 17:30 +0200, Antonios Motakis wrote:
>> On Wed, Sep 24, 2014 at 1:01 AM, Alex Williamson
>> <alex.williamson@redhat.com> wrote:
>> >
>> > On Tue, 2014-09-23 at 16:46 +0200, Antonios Motakis wrote:
>> > > Driver to bind to Linux platform devices, and callbacks to discover their
>> > > resources to be used by the main VFIO PLATFORM code.
>> > >
>> > > Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
>> > > ---
>> > >  drivers/vfio/platform/vfio_platform.c | 96 +++++++++++++++++++++++++++++++++++
>> > >  include/uapi/linux/vfio.h             |  1 +
>> > >  2 files changed, 97 insertions(+)
>> > >  create mode 100644 drivers/vfio/platform/vfio_platform.c
>> > >
>> > > diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
>> > > new file mode 100644
>> > > index 0000000..024c026
>> > > --- /dev/null
>> > > +++ b/drivers/vfio/platform/vfio_platform.c
>> > > @@ -0,0 +1,96 @@
>> > > +/*
>> > > + * Copyright (C) 2013 - Virtual Open Systems
>> > > + * Author: Antonios Motakis <a.motakis@virtualopensystems.com>
>> > > + *
>> > > + * This program is free software; you can redistribute it and/or modify
>> > > + * it under the terms of the GNU General Public License, version 2, as
>> > > + * published by the Free Software Foundation.
>> > > + *
>> > > + * This program is distributed in the hope that it will be useful,
>> > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> > > + * GNU General Public License for more details.
>> > > + */
>> > > +
>> > > +#include <linux/device.h>
>> > > +#include <linux/eventfd.h>
>> > > +#include <linux/interrupt.h>
>> > > +#include <linux/iommu.h>
>> > > +#include <linux/module.h>
>> > > +#include <linux/mutex.h>
>> > > +#include <linux/notifier.h>
>> > > +#include <linux/pm_runtime.h>
>> > > +#include <linux/slab.h>
>> > > +#include <linux/types.h>
>> > > +#include <linux/uaccess.h>
>> > > +#include <linux/vfio.h>
>> > > +#include <linux/io.h>
>> > > +#include <linux/platform_device.h>
>> > > +#include <linux/irq.h>
>> > > +
>> > > +#include "vfio_platform_private.h"
>> > > +
>> > > +#define DRIVER_VERSION  "0.7"
>> > > +#define DRIVER_AUTHOR   "Antonios Motakis <a.motakis@virtualopensystems.com>"
>> > > +#define DRIVER_DESC     "VFIO for platform devices - User Level meta-driver"
>> > > +
>> > > +/* probing devices from the linux platform bus */
>> > > +
>> > > +static struct resource *get_platform_resource(struct vfio_platform_device *vdev,
>> > > +                                             int i)
>> > > +{
>> > > +     struct platform_device *pdev = (struct platform_device *) vdev->opaque;
>> > > +
>> > > +     return platform_get_resource(pdev, IORESOURCE_MEM, i);
>> >
>> > ARM may only support IORESOURCE_MEM, but I don't think platform devices
>> > are limited to MMIO, right?  vfio-platform shouldn't be either.
>> >
>>
>> Indeed. Should we however implement this lacking a target to verify it
>> is working correctly?
>>
>> Leaving it out would mean PIO resources for those devices would not be
>> exposed before an update to VFIO, but we wouldn't have to break
>> backward compatibility I think.
>>
>> Would you prefer to have it implemented regardless?
>
> I think we need to have PIO figured out at least enough to have stubbed
> read/write handlers that could be filled in by someone with test
> hardware.  I'm not sure I fully understand how a user associates a
> region index to a device tree description, whether it's ordering or
> something more complicated, so I'm not sure if simply listing all the
> PIO resources after the MMIO resources is sufficient and compatible.
> Maybe you have some thoughts on that.  Thanks,

You are right. I'm not aware if the Linux calls used are guaranteed to
preserve ordering of PIO/MMIO resources, I will investigate a bit on
that.

>
> Alex
>
>> > > +}
>> > > +
>> > > +static int get_platform_irq(struct vfio_platform_device *vdev, int i)
>> > > +{
>> > > +     struct platform_device *pdev = (struct platform_device *) vdev->opaque;
>> > > +
>> > > +     return platform_get_irq(pdev, i);
>> > > +}
>> > > +
>> > > +
>> > > +static int vfio_platform_probe(struct platform_device *pdev)
>> > > +{
>> > > +     struct vfio_platform_device *vdev;
>> > > +     int ret;
>> > > +
>> > > +     vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
>> > > +     if (!vdev)
>> > > +             return -ENOMEM;
>> > > +
>> > > +     vdev->opaque = (void *) pdev;
>> > > +     vdev->name = pdev->name;
>> > > +     vdev->flags = VFIO_DEVICE_FLAGS_PLATFORM;
>> > > +     vdev->get_resource = get_platform_resource;
>> > > +     vdev->get_irq = get_platform_irq;
>> > > +
>> > > +     ret = vfio_platform_probe_common(vdev, &pdev->dev);
>> > > +     if (ret)
>> > > +             kfree(vdev);
>> > > +
>> > > +     return ret;
>> > > +}
>> > > +
>> > > +static int vfio_platform_remove(struct platform_device *pdev)
>> > > +{
>> > > +     return vfio_platform_remove_common(&pdev->dev);
>> > > +}
>> > > +
>> > > +static struct platform_driver vfio_platform_driver = {
>> > > +     .probe          = vfio_platform_probe,
>> > > +     .remove         = vfio_platform_remove,
>> > > +     .driver = {
>> > > +             .name   = "vfio-platform",
>> > > +             .owner  = THIS_MODULE,
>> > > +     },
>> > > +};
>> > > +
>> > > +module_platform_driver(vfio_platform_driver);
>> > > +
>> > > +MODULE_VERSION(DRIVER_VERSION);
>> > > +MODULE_LICENSE("GPL v2");
>> > > +MODULE_AUTHOR(DRIVER_AUTHOR);
>> > > +MODULE_DESCRIPTION(DRIVER_DESC);
>> > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> > > index 30f630c..b022a25 100644
>> > > --- a/include/uapi/linux/vfio.h
>> > > +++ b/include/uapi/linux/vfio.h
>> > > @@ -158,6 +158,7 @@ struct vfio_device_info {
>> > >       __u32   flags;
>> > >  #define VFIO_DEVICE_FLAGS_RESET      (1 << 0)        /* Device supports reset */
>> > >  #define VFIO_DEVICE_FLAGS_PCI        (1 << 1)        /* vfio-pci device */
>> > > +#define VFIO_DEVICE_FLAGS_PLATFORM (1 << 2)  /* vfio-platform device */
>> > >       __u32   num_regions;    /* Max region index + 1 */
>> > >       __u32   num_irqs;       /* Max IRQ index + 1 */
>> > >  };
>> >
>> >
>> >
>>
>>
>>
>
>
>

-- 
Antonios Motakis
Virtual Open Systems