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[PATCH 0/2] uio_msi: device driver

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  [PATCH 0/2] uio_msi: device driver Stephen Hemminger <stephen@networkplumber.org> - 2015-10-01 00:30 +0200
    [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-01 00:30 +0200
      Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 10:40 +0200
        Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 12:40 +0200
          Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 18:10 +0200
        Re: [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-01 17:00 +0200
          Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 17:30 +0200
        Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 18:40 +0200
          Re: [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-01 19:30 +0200
            Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 20:30 +0200
        Re: [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 00:00 +0200
          Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 00:50 +0200
            Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-06 09:40 +0200
              Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Avi Kivity <avi@scylladb.com> - 2015-10-06 14:20 +0200
                Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 16:10 +0200
                  Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Avi Kivity <avi@scylladb.com> - 2015-10-06 17:50 +0200
                Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Thomas Monjalon <thomas.monjalon@6wind.com> - 2015-10-16 19:20 +0200
                  Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-16 19:30 +0200
              Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 15:50 +0200
            Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 10:30 +0200
              Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 16:00 +0200
                Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 16:50 +0200
                  Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 17:10 +0200
                    Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 18:50 +0200
      Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-02 01:50 +0200
        Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-02 02:10 +0200
          Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-02 04:40 +0200
        Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Stephen Hemminger <stephen@networkplumber.org> - 2015-10-02 02:10 +0200
          Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-02 03:30 +0200
    [PATCH 1/2] uio: add support for ioctls Stephen Hemminger <stephen@networkplumber.org> - 2015-10-01 00:30 +0200
    Re: [PATCH 0/2] uio_msi: device driver "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-01 10:40 +0200
    Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Avi Kivity <avi@scylladb.com> - 2015-10-01 13:00 +0200
      Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Stephen Hemminger <stephen@networkplumber.org> - 2015-10-01 17:00 +0200
        Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-01 21:50 +0200
          Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Stephen Hemminger <stephen@networkplumber.org> - 2015-10-02 00:10 +0200
            Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-02 01:10 +0200
              Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Stephen Hemminger <stephen@networkplumber.org> - 2015-10-02 01:40 +0200
                Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-02 01:50 +0200
                  Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Stephen Hemminger <stephen@networkplumber.org> - 2015-10-02 02:10 +0200
                    Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Alexander Duyck <alexander.duyck@gmail.com> - 2015-10-02 03:40 +0200
                      Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-04 19:00 +0200
                        Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Greg KH <gregkh@linux-foundation.org> - 2015-10-04 21:10 +0200
                          Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-04 22:50 +0200

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#1240451 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On Tue, Oct 06, 2015 at 11:23:11AM +0300, Vlad Zolotarov wrote:
> Michael, how this or any other related patch is related to the problem u r
> describing?
> The above ability is there for years and if memory serves me
> well it was u who wrote uio_pci_generic with this "security flaw".  ;)

I answered all this already.

This patch enables bus mastering, enables MSI or MSI-X, and requires
userspace to map the MSI-X table and read/write the config space.
This means that a single userspace bug is enough to corrupt kernel
memory.

uio_pci_generic does not enable bus mastering or MSI, and
it might be a good idea to have uio_pci_generic block
access to MSI/MSI-X config.
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#1240511 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On 10/06/15 16:58, Michael S. Tsirkin wrote:
> On Tue, Oct 06, 2015 at 11:23:11AM +0300, Vlad Zolotarov wrote:
>> Michael, how this or any other related patch is related to the problem u r
>> describing?
>> The above ability is there for years and if memory serves me
>> well it was u who wrote uio_pci_generic with this "security flaw".  ;)
> I answered all this already.
>
> This patch enables bus mastering, enables MSI or MSI-X

This may be done from the user space right now without this patch...

> , and requires
> userspace to map the MSI-X table

Hmmm... I must have missed this requirement. Could u, pls., clarify? 
 From what I see, MSI/MSI-X table is configured completely in the kernel 
here...

> and read/write the config space.
> This means that a single userspace bug is enough to corrupt kernel
> memory.

Could u, pls., provide and example of this simple bug? Because it's 
absolutely not obvious...

>
> uio_pci_generic does not enable bus mastering or MSI, and
> it might be a good idea to have uio_pci_generic block
> access to MSI/MSI-X config.

Since device bars may be mapped bypassing the UIO/uio_pci_generic - this 
won't solve any issue.


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#1240528 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On Tue, Oct 06, 2015 at 05:49:21PM +0300, Vlad Zolotarov wrote:
> >and read/write the config space.
> >This means that a single userspace bug is enough to corrupt kernel
> >memory.
> 
> Could u, pls., provide and example of this simple bug? Because it's
> absolutely not obvious...

Stick a value that happens to match a kernel address in Msg Addr field
in an unmasked MSI-X entry.

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#1240725 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On 10/06/15 18:00, Michael S. Tsirkin wrote:
> On Tue, Oct 06, 2015 at 05:49:21PM +0300, Vlad Zolotarov wrote:
>>> and read/write the config space.
>>> This means that a single userspace bug is enough to corrupt kernel
>>> memory.
>> Could u, pls., provide and example of this simple bug? Because it's
>> absolutely not obvious...
> Stick a value that happens to match a kernel address in Msg Addr field
> in an unmasked MSI-X entry.

This patch neither configures MSI-X entries in the user space nor 
provides additional means to do so therefore this "sticking" would be a 
matter of some extra code that is absolutely unrelated to this patch. 
So, this example seems absolutely irrelevant to this particular discussion.

thanks,
vlad

>

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#1237835 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On 09/30/2015 03:28 PM, Stephen Hemminger wrote:
> This driver allows using PCI device with Message Signalled Interrupt
> from userspace. The API is similar to the igb_uio driver used by the DPDK.
> Via ioctl it provides a mechanism to map MSI-X interrupts into event
> file descriptors similar to VFIO.
>
> VFIO is a better choice if IOMMU is available, but often userspace drivers
> have to work in environments where IOMMU support (real or emulated) is
> not available.  All UIO drivers that support DMA are not secure against
> rogue userspace applications programming DMA hardware to access
> private memory; this driver is no less secure than existing code.
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>   drivers/uio/Kconfig          |   9 ++
>   drivers/uio/Makefile         |   1 +
>   drivers/uio/uio_msi.c        | 378 +++++++++++++++++++++++++++++++++++++++++++
>   include/uapi/linux/Kbuild    |   1 +
>   include/uapi/linux/uio_msi.h |  22 +++
>   5 files changed, 411 insertions(+)
>   create mode 100644 drivers/uio/uio_msi.c
>   create mode 100644 include/uapi/linux/uio_msi.h
>
> diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig
> index 52c98ce..04adfa0 100644
> --- a/drivers/uio/Kconfig
> +++ b/drivers/uio/Kconfig
> @@ -93,6 +93,15 @@ config UIO_PCI_GENERIC
>   	  primarily, for virtualization scenarios.
>   	  If you compile this as a module, it will be called uio_pci_generic.
>
> +config UIO_PCI_MSI
> +       tristate "Generic driver supporting MSI-x on PCI Express cards"
> +	depends on PCI
> +	help
> +	  Generic driver that provides Message Signalled IRQ events
> +	  similar to VFIO. If IOMMMU is available please use VFIO
> +	  instead since it provides more security.
> +	  If you compile this as a module, it will be called uio_msi.
> +
>   config UIO_NETX
>   	tristate "Hilscher NetX Card driver"
>   	depends on PCI

Should you maybe instead depend on CONFIG_PCI_MSI.  Without MSI this is 
essentially just uio_pci_generic with a bit more greedy mapping setup.

> diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
> index 8560dad..62fc44b 100644
> --- a/drivers/uio/Makefile
> +++ b/drivers/uio/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_UIO_NETX)	+= uio_netx.o
>   obj-$(CONFIG_UIO_PRUSS)         += uio_pruss.o
>   obj-$(CONFIG_UIO_MF624)         += uio_mf624.o
>   obj-$(CONFIG_UIO_FSL_ELBC_GPCM)	+= uio_fsl_elbc_gpcm.o
> +obj-$(CONFIG_UIO_PCI_MSI)	+= uio_msi.o
> diff --git a/drivers/uio/uio_msi.c b/drivers/uio/uio_msi.c
> new file mode 100644
> index 0000000..802b5c4
> --- /dev/null
> +++ b/drivers/uio/uio_msi.c
> @@ -0,0 +1,378 @@
> +/*-
> + *
> + * Copyright (c) 2015 by Brocade Communications Systems, Inc.
> + * Author: Stephen Hemminger <stephen@networkplumber.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 only.
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/device.h>
> +#include <linux/interrupt.h>
> +#include <linux/eventfd.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/uio_driver.h>
> +#include <linux/msi.h>
> +#include <linux/uio_msi.h>
> +
> +#define DRIVER_VERSION		"0.1.1"
> +#define MAX_MSIX_VECTORS	64
> +
> +/* MSI-X vector information */
> +struct uio_msi_pci_dev {
> +	struct uio_info info;		/* UIO driver info */
> +	struct pci_dev *pdev;		/* PCI device */
> +	struct mutex	mutex;		/* open/release/ioctl mutex */
> +	int		ref_cnt;	/* references to device */
> +	unsigned int	max_vectors;	/* MSI-X slots available */
> +	struct msix_entry *msix;	/* MSI-X vector table */
> +	struct uio_msi_irq_ctx {
> +		struct eventfd_ctx *trigger; /* vector to eventfd */
> +		char *name;		/* name in /proc/interrupts */
> +	} *ctx;
> +};
> +

I would move the definition of uio_msi_irq_ctx out of uio_msi_pci_dev. 
It would help to make this a bit more readable.

> +static irqreturn_t uio_intx_irqhandler(int irq, void *arg)
> +{
> +	struct uio_msi_pci_dev *udev = arg;
> +
> +	if (pci_check_and_mask_intx(udev->pdev)) {
> +		eventfd_signal(udev->ctx->trigger, 1);
> +		return IRQ_HANDLED;
> +	}
> +
> +	return IRQ_NONE;
> +}
> +

I would really prefer to see the intx handling dropped since there are 
already 2 different UIO drivers setup for handling INTx style 
interrupts.  Lets focus on the parts from the last decade and drop 
support for INTx now in favor of MSI-X and maybe MSI.  If we _REALLY_ 
need it we can always come back later and add it.

> +static irqreturn_t uio_msi_irqhandler(int irq, void *arg)
> +{
> +	struct eventfd_ctx *trigger = arg;
> +
> +	eventfd_signal(trigger, 1);
> +	return IRQ_HANDLED;
> +}
> +
> +/* set the mapping between vector # and existing eventfd. */
> +static int set_irq_eventfd(struct uio_msi_pci_dev *udev, u32 vec, int fd)
> +{
> +	struct eventfd_ctx *trigger;
> +	int irq, err;
> +
> +	if (vec >= udev->max_vectors) {
> +		dev_notice(&udev->pdev->dev, "vec %u >= num_vec %u\n",
> +			   vec, udev->max_vectors);
> +		return -ERANGE;
> +	}
> +
> +	irq = udev->msix[vec].vector;
> +	trigger = udev->ctx[vec].trigger;
> +	if (trigger) {
> +		/* Clearup existing irq mapping */

Minor spelling issue here, "Clear up" should be 2 words, "Cleanup" can 
be one.

> +		free_irq(irq, trigger);
> +		eventfd_ctx_put(trigger);
> +		udev->ctx[vec].trigger = NULL;
> +	}
> +
> +	/* Passing -1 is used to disable interrupt */
> +	if (fd < 0)
> +		return 0;
> +
> +	trigger = eventfd_ctx_fdget(fd);
> +	if (IS_ERR(trigger)) {
> +		err = PTR_ERR(trigger);
> +		dev_notice(&udev->pdev->dev,
> +			   "eventfd ctx get failed: %d\n", err);
> +		return err;
> +	}
> +
> +	if (udev->msix)
> +		err = request_irq(irq, uio_msi_irqhandler, 0,
> +				  udev->ctx[vec].name, trigger);
> +	else
> +		err = request_irq(irq, uio_intx_irqhandler, IRQF_SHARED,
> +				  udev->ctx[vec].name, udev);
> +
> +	if (err) {
> +		dev_notice(&udev->pdev->dev,
> +			   "request irq failed: %d\n", err);
> +		eventfd_ctx_put(trigger);
> +		return err;
> +	}
> +
> +	udev->ctx[vec].trigger = trigger;
> +	return 0;
> +}
> +
> +static int
> +uio_msi_ioctl(struct uio_info *info, unsigned int cmd, unsigned long arg)
> +{
> +	struct uio_msi_pci_dev *udev
> +		= container_of(info, struct uio_msi_pci_dev, info);
> +	struct uio_msi_irq_set hdr;
> +	int err;
> +
> +	switch (cmd) {
> +	case UIO_MSI_IRQ_SET:
> +		if (copy_from_user(&hdr, (void __user *)arg, sizeof(hdr)))
> +			return -EFAULT;
> +
> +		mutex_lock(&udev->mutex);
> +		err = set_irq_eventfd(udev, hdr.vec, hdr.fd);
> +		mutex_unlock(&udev->mutex);
> +		break;
> +	default:
> +		err = -EOPNOTSUPP;
> +	}
> +	return err;
> +}
> +
> +/* Opening the UIO device for first time enables MSI-X */
> +static int
> +uio_msi_open(struct uio_info *info, struct inode *inode)
> +{
> +	struct uio_msi_pci_dev *udev
> +		= container_of(info, struct uio_msi_pci_dev, info);
> +	int err = 0;
> +
> +	mutex_lock(&udev->mutex);
> +	if (udev->ref_cnt++ == 0) {
> +		if (udev->msix)
> +			err = pci_enable_msix(udev->pdev, udev->msix,
> +					      udev->max_vectors);
> +	}
> +	mutex_unlock(&udev->mutex);
> +
> +	return err;
> +}
> +

I agree with some other reviewers.  Why call pci_enable_msix in open? 
It seems like it would make much more sense to do this on probe, and 
then disable MSI-X on free.  I can only assume you are trying to do it 
to save on resources but the fact is this is a driver you have to 
explicitly force onto a device so you would probably be safe to assume 
that they plan to use it in the near future.

> +/* Last close of the UIO device releases/disables all IRQ's */
> +static int
> +uio_msi_release(struct uio_info *info, struct inode *inode)
> +{
> +	struct uio_msi_pci_dev *udev
> +		= container_of(info, struct uio_msi_pci_dev, info);
> +	int i;
> +
> +	mutex_lock(&udev->mutex);
> +	if (--udev->ref_cnt == 0) {
> +		for (i = 0; i < udev->max_vectors; i++) {
> +			int irq = udev->msix[i].vector;
> +			struct eventfd_ctx *trigger = udev->ctx[i].trigger;
> +
> +			if (!trigger)
> +				continue;
> +
> +			free_irq(irq, trigger);
> +			eventfd_ctx_put(trigger);
> +			udev->ctx[i].trigger = NULL;
> +		}
> +
> +		if (udev->msix)
> +			pci_disable_msix(udev->pdev);
> +	}
> +	mutex_unlock(&udev->mutex);
> +
> +	return 0;
> +}
> +
> +/* Unmap previously ioremap'd resources */
> +static void
> +release_iomaps(struct uio_mem *mem)
> +{
> +	int i;
> +
> +	for (i = 0; i < MAX_UIO_MAPS; i++, mem++) {
> +		if (mem->internal_addr)
> +			iounmap(mem->internal_addr);
> +	}
> +}
> +
> +static int
> +setup_maps(struct pci_dev *pdev, struct uio_info *info)
> +{
> +	int i, m = 0, p = 0, err;
> +	static const char * const bar_names[] = {
> +		"BAR0",	"BAR1",	"BAR2",	"BAR3",	"BAR4",	"BAR5",
> +	};
> +
> +	for (i = 0; i < ARRAY_SIZE(bar_names); i++) {
> +		unsigned long start = pci_resource_start(pdev, i);
> +		unsigned long flags = pci_resource_flags(pdev, i);
> +		unsigned long len = pci_resource_len(pdev, i);
> +
> +		if (start == 0 || len == 0)
> +			continue;
> +
> +		if (flags & IORESOURCE_MEM) {
> +			void __iomem *addr;
> +
> +			if (m >= MAX_UIO_MAPS)
> +				continue;
> +
> +			addr = ioremap(start, len);
> +			if (addr == NULL) {
> +				err = -EINVAL;
> +				goto fail;
> +			}
> +
> +			info->mem[m].name = bar_names[i];
> +			info->mem[m].addr = start;
> +			info->mem[m].internal_addr = addr;
> +			info->mem[m].size = len;
> +			info->mem[m].memtype = UIO_MEM_PHYS;
> +			++m;
> +		} else if (flags & IORESOURCE_IO) {
> +			if (p >= MAX_UIO_PORT_REGIONS)
> +				continue;
> +
> +			info->port[p].name = bar_names[i];
> +			info->port[p].start = start;
> +			info->port[p].size = len;
> +			info->port[p].porttype = UIO_PORT_X86;
> +			++p;
> +		}
> +	}
> +
> +	return 0;
> + fail:
> +	for (i = 0; i < m; i++)
> +		iounmap(info->mem[i].internal_addr);
> +	return err;
> +}
> +

Do you really need to map IORESOURCE bars?  Most drivers I can think of 
don't use IO BARs anymore.  Maybe we could look at just dropping the 
code and adding it back later if we have a use case that absolutely 
needs it.

Also how many devices actually need resources beyond BAR 0?  I'm just 
curious as I know BAR 2 on many of the Intel devices is the register 
space related to MSI-X so now we have both the PCIe subsystem and user 
space with access to this region.

> +static int uio_msi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> +{
> +	struct uio_msi_pci_dev *udev;
> +	int i, err, vectors;
> +
> +	udev = kzalloc(sizeof(struct uio_msi_pci_dev), GFP_KERNEL);
> +	if (!udev)
> +		return -ENOMEM;
> +
> +	err = pci_enable_device(pdev);
> +	if (err != 0) {
> +		dev_err(&pdev->dev, "cannot enable PCI device\n");
> +		goto fail_free;
> +	}
> +
> +	err = pci_request_regions(pdev, "uio_msi");
> +	if (err != 0) {
> +		dev_err(&pdev->dev, "Cannot request regions\n");
> +		goto fail_disable;
> +	}
> +
> +	pci_set_master(pdev);
> +
> +	/* remap resources */
> +	err = setup_maps(pdev, &udev->info);
> +	if (err)
> +		goto fail_release_iomem;
> +
> +	/* fill uio infos */
> +	udev->info.name = "uio_msi";
> +	udev->info.version = DRIVER_VERSION;
> +	udev->info.priv = udev;
> +	udev->pdev = pdev;
> +	udev->info.ioctl = uio_msi_ioctl;
> +	udev->info.open = uio_msi_open;
> +	udev->info.release = uio_msi_release;
> +	udev->info.irq = UIO_IRQ_CUSTOM;
> +	mutex_init(&udev->mutex);
> +
> +	vectors = pci_msix_vec_count(pdev);
> +	if (vectors > 0) {
> +		udev->max_vectors = min_t(u16, vectors, MAX_MSIX_VECTORS);
> +		dev_info(&pdev->dev, "using up to %u MSI-X vectors\n",
> +			udev->max_vectors);
> +
> +		err = -ENOMEM;
> +		udev->msix = kcalloc(udev->max_vectors,
> +				     sizeof(struct msix_entry), GFP_KERNEL);
> +		if (!udev->msix)
> +			goto fail_release_iomem;
> +	} else if (!pci_intx_mask_supported(pdev)) {
> +		dev_err(&pdev->dev,
> +			"device does not support MSI-X or INTX\n");
> +		err = -EINVAL;
> +		goto fail_release_iomem;
> +	} else {
> +		dev_notice(&pdev->dev, "using INTX\n");
> +		udev->info.irq_flags = IRQF_SHARED;
> +		udev->max_vectors = 1;
> +	}
> +
> +	udev->ctx = kcalloc(udev->max_vectors,
> +			    sizeof(struct uio_msi_irq_ctx), GFP_KERNEL);
> +	if (!udev->ctx)
> +		goto fail_free_msix;
> +
> +	for (i = 0; i < udev->max_vectors; i++) {
> +		udev->msix[i].entry = i;
> +
> +		udev->ctx[i].name = kasprintf(GFP_KERNEL,
> +					      KBUILD_MODNAME "[%d](%s)",
> +					      i, pci_name(pdev));
> +		if (!udev->ctx[i].name)
> +			goto fail_free_ctx;
> +	}
> +
> +	/* register uio driver */
> +	err = uio_register_device(&pdev->dev, &udev->info);
> +	if (err != 0)
> +		goto fail_free_ctx;
> +
> +	pci_set_drvdata(pdev, udev);
> +	return 0;
> +
> +fail_free_ctx:
> +	for (i = 0; i < udev->max_vectors; i++)
> +		kfree(udev->ctx[i].name);
> +	kfree(udev->ctx);
> +fail_free_msix:
> +	kfree(udev->msix);
> +fail_release_iomem:
> +	release_iomaps(udev->info.mem);
> +	pci_release_regions(pdev);
> +fail_disable:
> +	pci_disable_device(pdev);
> +fail_free:
> +	kfree(udev);
> +
> +	pr_notice("%s ret %d\n", __func__, err);
> +	return err;
> +}
> +
> +static void uio_msi_remove(struct pci_dev *pdev)
> +{
> +	struct uio_info *info = pci_get_drvdata(pdev);
> +	struct uio_msi_pci_dev *udev
> +		= container_of(info, struct uio_msi_pci_dev, info);
> +	int i;
> +
> +	uio_unregister_device(info);
> +	release_iomaps(info->mem);
> +
> +	pci_release_regions(pdev);
> +	for (i = 0; i < udev->max_vectors; i++)
> +		kfree(udev->ctx[i].name);
> +	kfree(udev->ctx);
> +	kfree(udev->msix);
> +	pci_disable_device(pdev);
> +
> +	pci_set_drvdata(pdev, NULL);
> +	kfree(udev);
> +}
> +
> +static struct pci_driver uio_msi_pci_driver = {
> +	.name = "uio_msi",
> +	.probe = uio_msi_probe,
> +	.remove = uio_msi_remove,
> +};
> +
> +module_pci_driver(uio_msi_pci_driver);
> +MODULE_VERSION(DRIVER_VERSION);
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Stephen Hemminger <stephen@networkplumber.org>");
> +MODULE_DESCRIPTION("UIO driver for MSI PCI devices");
> diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
> index f7b2db4..d9497691 100644
> --- a/include/uapi/linux/Kbuild
> +++ b/include/uapi/linux/Kbuild
> @@ -411,6 +411,7 @@ header-y += udp.h
>   header-y += uhid.h
>   header-y += uinput.h
>   header-y += uio.h
> +header-y += uio_msi.h
>   header-y += ultrasound.h
>   header-y += un.h
>   header-y += unistd.h
> diff --git a/include/uapi/linux/uio_msi.h b/include/uapi/linux/uio_msi.h
> new file mode 100644
> index 0000000..297de00
> --- /dev/null
> +++ b/include/uapi/linux/uio_msi.h
> @@ -0,0 +1,22 @@
> +/*
> + * UIO_MSI API definition
> + *
> + * Copyright (c) 2015 by Brocade Communications Systems, Inc.
> + * All rights reserved.
> + *
> + * 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.
> + */
> +#ifndef _UIO_PCI_MSI_H
> +#define _UIO_PCI_MSI_H
> +
> +struct uio_msi_irq_set {
> +	u32 vec;
> +	int fd;
> +};
> +
> +#define UIO_MSI_BASE	0x86
> +#define UIO_MSI_IRQ_SET	_IOW('I', UIO_MSI_BASE+1, struct uio_msi_irq_set)
> +
> +#endif
>

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#1237838 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On Thu, 1 Oct 2015 16:40:10 -0700
Alexander Duyck <alexander.duyck@gmail.com> wrote:

> Do you really need to map IORESOURCE bars?  Most drivers I can think of 
> don't use IO BARs anymore.  Maybe we could look at just dropping the 
> code and adding it back later if we have a use case that absolutely 
> needs it.
Mapping is not strictly necessary, but for virtio it acts a way to communicate
the regions.

> Also how many devices actually need resources beyond BAR 0?  I'm just 
> curious as I know BAR 2 on many of the Intel devices is the register 
> space related to MSI-X so now we have both the PCIe subsystem and user 
> space with access to this region.

VMXNet3 needs 2 bars. Most use only one.
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#1237883 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On 10/01/2015 05:04 PM, Stephen Hemminger wrote:
> On Thu, 1 Oct 2015 16:40:10 -0700
> Alexander Duyck <alexander.duyck@gmail.com> wrote:
>
>> Do you really need to map IORESOURCE bars?  Most drivers I can think of
>> don't use IO BARs anymore.  Maybe we could look at just dropping the
>> code and adding it back later if we have a use case that absolutely
>> needs it.
> Mapping is not strictly necessary, but for virtio it acts a way to communicate
> the regions.

I think I see what you are saying.  I was hoping we could get away from 
having to map any I/O ports but it looks like virtio is still using them 
for BAR 0, or at least that is what I am seeing on my VM with 
virtio_net.  I was really hoping we could get away from that since a 16b 
address space is far too restrictive anyway.

>> Also how many devices actually need resources beyond BAR 0?  I'm just
>> curious as I know BAR 2 on many of the Intel devices is the register
>> space related to MSI-X so now we have both the PCIe subsystem and user
>> space with access to this region.
> VMXNet3 needs 2 bars. Most use only one.

So essentially we are needing to make exceptions for the virtual interfaces.

I guess there isn't much we can do then and we probably need to map any 
and all base address registers we can find for the given device.  I was 
hoping for something a bit more surgical since we are opening a security 
hole of sorts, but I guess it can't be helped if we want to support 
multiple devices and they all have such radically different configurations.

- Alex
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#1237842 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On Thu, 1 Oct 2015 16:40:10 -0700
Alexander Duyck <alexander.duyck@gmail.com> wrote:

> I agree with some other reviewers.  Why call pci_enable_msix in open? 
> It seems like it would make much more sense to do this on probe, and 
> then disable MSI-X on free.  I can only assume you are trying to do it 
> to save on resources but the fact is this is a driver you have to 
> explicitly force onto a device so you would probably be safe to assume 
> that they plan to use it in the near future.

Because if interface is not up, the MSI handle doesn't have to be open.
This saves resources and avoids some races.
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#1237870 — Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X

On 10/01/2015 05:01 PM, Stephen Hemminger wrote:
> On Thu, 1 Oct 2015 16:40:10 -0700
> Alexander Duyck <alexander.duyck@gmail.com> wrote:
>
>> I agree with some other reviewers.  Why call pci_enable_msix in open?
>> It seems like it would make much more sense to do this on probe, and
>> then disable MSI-X on free.  I can only assume you are trying to do it
>> to save on resources but the fact is this is a driver you have to
>> explicitly force onto a device so you would probably be safe to assume
>> that they plan to use it in the near future.
> Because if interface is not up, the MSI handle doesn't have to be open.
> This saves resources and avoids some races.

Yes, but it makes things a bit messier for the interrupts.  Most drivers 
take care of interrupts during probe so that if there are any allocation 
problems they can take care of them then instead of leaving an interface 
out that will later fail when it is brought up.  It ends up being a way 
to deal with the whole MSI-X fall-back issue.

- Alex
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#1236833 — [PATCH 1/2] uio: add support for ioctls

Allow UIO device driver to provide ioctl interface.
This allow additional API's for UIO.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 drivers/uio/uio.c          | 15 +++++++++++++++
 include/linux/uio_driver.h |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 8196581..5ab32ab 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -576,6 +576,20 @@ static ssize_t uio_write(struct file *filep, const char __user *buf,
 	return retval ? retval : sizeof(s32);
 }
 
+static long uio_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+	struct uio_listener *listener = filep->private_data;
+	struct uio_device *idev = listener->dev;
+
+	if (!idev->info)
+		return -EIO;
+
+	if (!idev->info->ioctl)
+		return -ENOTTY;
+
+	return idev->info->ioctl(idev->info, cmd, arg);
+}
+
 static int uio_find_mem_index(struct vm_area_struct *vma)
 {
 	struct uio_device *idev = vma->vm_private_data;
@@ -712,6 +726,7 @@ static const struct file_operations uio_fops = {
 	.write		= uio_write,
 	.mmap		= uio_mmap,
 	.poll		= uio_poll,
+	.unlocked_ioctl	= uio_ioctl,
 	.fasync		= uio_fasync,
 	.llseek		= noop_llseek,
 };
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 32c0e83..10d7833 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -89,6 +89,7 @@ struct uio_device {
  * @mmap:		mmap operation for this uio device
  * @open:		open operation for this uio device
  * @release:		release operation for this uio device
+ * @ioctl:		ioctl handler
  * @irqcontrol:		disable/enable irqs when 0/1 is written to /dev/uioX
  */
 struct uio_info {
@@ -105,6 +106,8 @@ struct uio_info {
 	int (*open)(struct uio_info *info, struct inode *inode);
 	int (*release)(struct uio_info *info, struct inode *inode);
 	int (*irqcontrol)(struct uio_info *info, s32 irq_on);
+	int (*ioctl)(struct uio_info *info, unsigned int cmd,
+		     unsigned long arg);
 };
 
 extern int __must_check
-- 
2.1.4

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#1237138

On Wed, Sep 30, 2015 at 03:28:56PM -0700, Stephen Hemminger wrote:
> This is a new UIO device driver to allow supporting MSI-X and MSI devices
> in userspace.  It has been used in environments like VMware and older versions
> of QEMU/KVM where no IOMMU support is available.
> 
> Stephen Hemminger (2):
> 
> *** BLURB HERE ***

I think this needs some more work to make sure
userspace can drive devices without a risk of
crashing the kernel even when there's no IOMMU.

I sent some comments in response to the patch itself.

Please copy me on future versions of this driver.

Thanks!

> Stephen Hemminger (2):
>   uio: add support for ioctls
>   uio: new driver to support PCI MSI-X
> 
>  drivers/uio/Kconfig          |   9 ++
>  drivers/uio/Makefile         |   1 +
>  drivers/uio/uio.c            |  15 ++
>  drivers/uio/uio_msi.c        | 378 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/uio_driver.h   |   3 +
>  include/uapi/linux/Kbuild    |   1 +
>  include/uapi/linux/uio_msi.h |  22 +++
>  7 files changed, 429 insertions(+)
>  create mode 100644 drivers/uio/uio_msi.c
>  create mode 100644 include/uapi/linux/uio_msi.h
> 
> -- 
> 2.1.4
> 
> --
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#1237265 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
> This is a new UIO device driver to allow supporting MSI-X and MSI devices
> in userspace.  It has been used in environments like VMware and older versions
> of QEMU/KVM where no IOMMU support is available.

Why not add msi/msix support to uio_pci_generic?

> Stephen Hemminger (2):
>
> *** BLURB HERE ***
>
> Stephen Hemminger (2):
>    uio: add support for ioctls
>    uio: new driver to support PCI MSI-X
>
>   drivers/uio/Kconfig          |   9 ++
>   drivers/uio/Makefile         |   1 +
>   drivers/uio/uio.c            |  15 ++
>   drivers/uio/uio_msi.c        | 378 +++++++++++++++++++++++++++++++++++++++++++
>   include/linux/uio_driver.h   |   3 +
>   include/uapi/linux/Kbuild    |   1 +
>   include/uapi/linux/uio_msi.h |  22 +++
>   7 files changed, 429 insertions(+)
>   create mode 100644 drivers/uio/uio_msi.c
>   create mode 100644 include/uapi/linux/uio_msi.h
>

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#1237481 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On Thu, 1 Oct 2015 13:59:02 +0300
Avi Kivity <avi@scylladb.com> wrote:

> On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
> > This is a new UIO device driver to allow supporting MSI-X and MSI devices
> > in userspace.  It has been used in environments like VMware and older versions
> > of QEMU/KVM where no IOMMU support is available.  
> 
> Why not add msi/msix support to uio_pci_generic?

That is possible but that would meet ABI and other resistance from the author.
Also, uio_pci_generic makes it harder to find resources since it doesn't fully
utilize UIO infrastructure.
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#1237688 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On 10/01/2015 07:57 AM, Stephen Hemminger wrote:
> On Thu, 1 Oct 2015 13:59:02 +0300
> Avi Kivity <avi@scylladb.com> wrote:
>
>> On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
>>> This is a new UIO device driver to allow supporting MSI-X and MSI devices
>>> in userspace.  It has been used in environments like VMware and older versions
>>> of QEMU/KVM where no IOMMU support is available.
>> Why not add msi/msix support to uio_pci_generic?
> That is possible but that would meet ABI and other resistance from the author.
> Also, uio_pci_generic makes it harder to find resources since it doesn't fully
> utilize UIO infrastructure.

I'd say you are better off actually taking this in the other direction.  
From what I have seen it seems like this driver is meant to deal with 
mapping VFs contained inside of guests.  If you are going to fork off 
and create a UIO driver for mapping VFs why not just make it specialize 
in that.  You could probably simplify the code by dropping support for 
legacy interrupts and IO regions since all that is already covered by 
uio_pci_generic anyway if I am not mistaken.

You could then look at naming it something like uio_vf since the uio_msi 
is a bit of a misnomer since it is MSI-X it supports, not MSI interrupts.

- Alex
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#1237774 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On Thu, 1 Oct 2015 12:48:36 -0700
Alexander Duyck <alexander.duyck@gmail.com> wrote:

> On 10/01/2015 07:57 AM, Stephen Hemminger wrote:
> > On Thu, 1 Oct 2015 13:59:02 +0300
> > Avi Kivity <avi@scylladb.com> wrote:
> >
> >> On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
> >>> This is a new UIO device driver to allow supporting MSI-X and MSI devices
> >>> in userspace.  It has been used in environments like VMware and older versions
> >>> of QEMU/KVM where no IOMMU support is available.
> >> Why not add msi/msix support to uio_pci_generic?
> > That is possible but that would meet ABI and other resistance from the author.
> > Also, uio_pci_generic makes it harder to find resources since it doesn't fully
> > utilize UIO infrastructure.
> 
> I'd say you are better off actually taking this in the other direction.  
> From what I have seen it seems like this driver is meant to deal with 
> mapping VFs contained inside of guests.  If you are going to fork off 
> and create a UIO driver for mapping VFs why not just make it specialize 
> in that.  You could probably simplify the code by dropping support for 
> legacy interrupts and IO regions since all that is already covered by 
> uio_pci_generic anyway if I am not mistaken.
> 
> You could then look at naming it something like uio_vf since the uio_msi 
> is a bit of a misnomer since it is MSI-X it supports, not MSI interrupts.

The support needs to cover:
  - VF in guest
  - VNIC in guest (vmxnet3)
it isn't just about VF's
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#1237823 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On 10/01/2015 03:00 PM, Stephen Hemminger wrote:
> On Thu, 1 Oct 2015 12:48:36 -0700
> Alexander Duyck <alexander.duyck@gmail.com> wrote:
>
>> On 10/01/2015 07:57 AM, Stephen Hemminger wrote:
>>> On Thu, 1 Oct 2015 13:59:02 +0300
>>> Avi Kivity <avi@scylladb.com> wrote:
>>>
>>>> On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
>>>>> This is a new UIO device driver to allow supporting MSI-X and MSI devices
>>>>> in userspace.  It has been used in environments like VMware and older versions
>>>>> of QEMU/KVM where no IOMMU support is available.
>>>> Why not add msi/msix support to uio_pci_generic?
>>> That is possible but that would meet ABI and other resistance from the author.
>>> Also, uio_pci_generic makes it harder to find resources since it doesn't fully
>>> utilize UIO infrastructure.
>> I'd say you are better off actually taking this in the other direction.
>>  From what I have seen it seems like this driver is meant to deal with
>> mapping VFs contained inside of guests.  If you are going to fork off
>> and create a UIO driver for mapping VFs why not just make it specialize
>> in that.  You could probably simplify the code by dropping support for
>> legacy interrupts and IO regions since all that is already covered by
>> uio_pci_generic anyway if I am not mistaken.
>>
>> You could then look at naming it something like uio_vf since the uio_msi
>> is a bit of a misnomer since it is MSI-X it supports, not MSI interrupts.
> The support needs to cover:
>    - VF in guest
>    - VNIC in guest (vmxnet3)
> it isn't just about VF's

I get that, but the driver you are talking about adding is duplicating 
much of what is already there in uio_pci_generic.  If nothing else it 
might be worth while to look at replacing the legacy interrupt with 
MSI.  Maybe look at naming it something like uio_pcie to indicate that 
we are focusing on assigning PCIe and virtual devices that support MSI 
and MSI-X and use memory BARs rather than legacy PCI devices that are 
doing things like mapping I/O BARs and using INTx signaling.

My main argument is that we should probably look at dropping support for 
anything that isn't going to be needed.  If it is really important we 
can always add it later.  I just don't see the value in having code 
around for things we aren't likely to ever use with real devices as we 
are stuck supporting it for the life of the driver. I'll go ahead and 
provide a inline review of your patch 2/2 as I think my feedback might 
make a bit more sense that way.

- Alex



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#1237831 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On Thu, 1 Oct 2015 16:03:06 -0700
Alexander Duyck <alexander.duyck@gmail.com> wrote:

> On 10/01/2015 03:00 PM, Stephen Hemminger wrote:
> > On Thu, 1 Oct 2015 12:48:36 -0700
> > Alexander Duyck <alexander.duyck@gmail.com> wrote:
> >
> >> On 10/01/2015 07:57 AM, Stephen Hemminger wrote:
> >>> On Thu, 1 Oct 2015 13:59:02 +0300
> >>> Avi Kivity <avi@scylladb.com> wrote:
> >>>
> >>>> On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
> >>>>> This is a new UIO device driver to allow supporting MSI-X and MSI devices
> >>>>> in userspace.  It has been used in environments like VMware and older versions
> >>>>> of QEMU/KVM where no IOMMU support is available.
> >>>> Why not add msi/msix support to uio_pci_generic?
> >>> That is possible but that would meet ABI and other resistance from the author.
> >>> Also, uio_pci_generic makes it harder to find resources since it doesn't fully
> >>> utilize UIO infrastructure.
> >> I'd say you are better off actually taking this in the other direction.
> >>  From what I have seen it seems like this driver is meant to deal with
> >> mapping VFs contained inside of guests.  If you are going to fork off
> >> and create a UIO driver for mapping VFs why not just make it specialize
> >> in that.  You could probably simplify the code by dropping support for
> >> legacy interrupts and IO regions since all that is already covered by
> >> uio_pci_generic anyway if I am not mistaken.
> >>
> >> You could then look at naming it something like uio_vf since the uio_msi
> >> is a bit of a misnomer since it is MSI-X it supports, not MSI interrupts.
> > The support needs to cover:
> >    - VF in guest
> >    - VNIC in guest (vmxnet3)
> > it isn't just about VF's
> 
> I get that, but the driver you are talking about adding is duplicating 
> much of what is already there in uio_pci_generic.  If nothing else it 
> might be worth while to look at replacing the legacy interrupt with 
> MSI.  Maybe look at naming it something like uio_pcie to indicate that 
> we are focusing on assigning PCIe and virtual devices that support MSI 
> and MSI-X and use memory BARs rather than legacy PCI devices that are 
> doing things like mapping I/O BARs and using INTx signaling.
> 
> My main argument is that we should probably look at dropping support for 
> anything that isn't going to be needed.  If it is really important we 
> can always add it later.  I just don't see the value in having code 
> around for things we aren't likely to ever use with real devices as we 
> are stuck supporting it for the life of the driver. I'll go ahead and 
> provide a inline review of your patch 2/2 as I think my feedback might 
> make a bit more sense that way.

Ok, but having one driver that can deal with failures with msi-x vector
setup and fallback seemed like a better strategy.


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#1237834 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On 10/01/2015 04:39 PM, Stephen Hemminger wrote:
> On Thu, 1 Oct 2015 16:03:06 -0700
> Alexander Duyck <alexander.duyck@gmail.com> wrote:
>
>> On 10/01/2015 03:00 PM, Stephen Hemminger wrote:
>>> On Thu, 1 Oct 2015 12:48:36 -0700
>>> Alexander Duyck <alexander.duyck@gmail.com> wrote:
>>>
>>>> On 10/01/2015 07:57 AM, Stephen Hemminger wrote:
>>>>> On Thu, 1 Oct 2015 13:59:02 +0300
>>>>> Avi Kivity <avi@scylladb.com> wrote:
>>>>>
>>>>>> On 10/01/2015 01:28 AM, Stephen Hemminger wrote:
>>>>>>> This is a new UIO device driver to allow supporting MSI-X and MSI devices
>>>>>>> in userspace.  It has been used in environments like VMware and older versions
>>>>>>> of QEMU/KVM where no IOMMU support is available.
>>>>>> Why not add msi/msix support to uio_pci_generic?
>>>>> That is possible but that would meet ABI and other resistance from the author.
>>>>> Also, uio_pci_generic makes it harder to find resources since it doesn't fully
>>>>> utilize UIO infrastructure.
>>>> I'd say you are better off actually taking this in the other direction.
>>>>   From what I have seen it seems like this driver is meant to deal with
>>>> mapping VFs contained inside of guests.  If you are going to fork off
>>>> and create a UIO driver for mapping VFs why not just make it specialize
>>>> in that.  You could probably simplify the code by dropping support for
>>>> legacy interrupts and IO regions since all that is already covered by
>>>> uio_pci_generic anyway if I am not mistaken.
>>>>
>>>> You could then look at naming it something like uio_vf since the uio_msi
>>>> is a bit of a misnomer since it is MSI-X it supports, not MSI interrupts.
>>> The support needs to cover:
>>>     - VF in guest
>>>     - VNIC in guest (vmxnet3)
>>> it isn't just about VF's
>> I get that, but the driver you are talking about adding is duplicating
>> much of what is already there in uio_pci_generic.  If nothing else it
>> might be worth while to look at replacing the legacy interrupt with
>> MSI.  Maybe look at naming it something like uio_pcie to indicate that
>> we are focusing on assigning PCIe and virtual devices that support MSI
>> and MSI-X and use memory BARs rather than legacy PCI devices that are
>> doing things like mapping I/O BARs and using INTx signaling.
>>
>> My main argument is that we should probably look at dropping support for
>> anything that isn't going to be needed.  If it is really important we
>> can always add it later.  I just don't see the value in having code
>> around for things we aren't likely to ever use with real devices as we
>> are stuck supporting it for the life of the driver. I'll go ahead and
>> provide a inline review of your patch 2/2 as I think my feedback might
>> make a bit more sense that way.
> Ok, but having one driver that can deal with failures with msi-x vector
> setup and fallback seemed like a better strategy.

Yes, but in the case of something like a VF it is going to just make a 
bigger mess of things since INTx doesn't work.  So what would you expect 
your driver to do in that case?  Also we have to keep in mind that the 
MSI-X failure case is very unlikely.

One other thing that just occurred to me is that you may want to try 
using the range allocation call instead of a hard set number of 
interrupts.  Then if you start running short on vectors you don't hard 
fail and instead just allocate what you can.

- Alex
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#1237840 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On Thu, 1 Oct 2015 16:43:23 -0700
Alexander Duyck <alexander.duyck@gmail.com> wrote:

> Yes, but in the case of something like a VF it is going to just make a 
> bigger mess of things since INTx doesn't work.  So what would you expect 
> your driver to do in that case?  Also we have to keep in mind that the 
> MSI-X failure case is very unlikely.
> 
> One other thing that just occurred to me is that you may want to try 
> using the range allocation call instead of a hard set number of 
> interrupts.  Then if you start running short on vectors you don't hard 
> fail and instead just allocate what you can.

I tried that but the bookkeeping gets messy since there is no good
way to communicate that back to userspace and have it adapt.
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#1237876 — Re: [dpdk-dev] [PATCH 0/2] uio_msi: device driver

On 10/01/2015 05:04 PM, Stephen Hemminger wrote:
> On Thu, 1 Oct 2015 16:43:23 -0700
> Alexander Duyck <alexander.duyck@gmail.com> wrote:
>
>> Yes, but in the case of something like a VF it is going to just make a
>> bigger mess of things since INTx doesn't work.  So what would you expect
>> your driver to do in that case?  Also we have to keep in mind that the
>> MSI-X failure case is very unlikely.
>>
>> One other thing that just occurred to me is that you may want to try
>> using the range allocation call instead of a hard set number of
>> interrupts.  Then if you start running short on vectors you don't hard
>> fail and instead just allocate what you can.
> I tried that but the bookkeeping gets messy since there is no good
> way to communicate that back to userspace and have it adapt.

Actually I kind of just realized that uio_msi_open is kind of messed 
up.  So if the MSI-X allocation fails due to no resources it will return 
a positive value indicating the number of vectors that could be 
allocated, a negative value if one of the input values is invalid, or 
0.  I'm not sure if returning a positive value on failure is an issue or 
not.  I know the open call is supposed to return a negative value or the 
file descriptor if not negative.  I don't know if the return value might 
be interpreted as a file descriptor or not.

Also if MSI-X is supported by the hardware, but disabled for some reason 
by the kernel ("pci=nomsi")  then this driver is rendered inoperable 
since it will never give you anything but -EINVAL from the open call.

I really think you should probably look at taking care of enabling MSI-X 
and maybe MSI as a fall-back in probe.  At least then you can post a 
message about how many vectors are enabled and what type. Then if you 
cannot enable any interrupts due to MSI being disabled you can simply 
fail at probe time and let then load a different driver.

- Alex
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