[Qemu-devel] Re: [PATCH v3 1/1] Shared memory uio_pci driver

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Mar 25, 2010 at 10:30:42AM -0600, Cam Macdonell wrote:
> On Thu, Mar 25, 2010 at 3:05 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Thu, Mar 25, 2010 at 12:09:36AM -0600, Cam Macdonell wrote:
> >> This patch adds a driver for my shared memory PCI device using the uio_pci
> >> interface.  The driver has three memory regions.  The first memory region is for
> >> device registers for sending interrupts. The second BAR is for receiving MSI-X
> >> interrupts and the third memory region maps the shared memory.  The device only
> >> exports the first and third memory regions to userspace.
> >>
> >> This driver supports MSI-X and regular pin interrupts.  Currently, the number of
> >> MSI vectors is set to 4 which could be increased, but the driver will work with
> >> fewer vectors.  If MSI is not available, then regular interrupts will be used.
> >> ---
> >>  drivers/uio/Kconfig       |    8 ++
> >>  drivers/uio/Makefile      |    1 +
> >>  drivers/uio/uio_ivshmem.c |  235 +++++++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 244 insertions(+), 0 deletions(-)
> >>  create mode 100644 drivers/uio/uio_ivshmem.c
> >>
> >> diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig
> >> index 1da73ec..b92cded 100644
> >> --- a/drivers/uio/Kconfig
> >> +++ b/drivers/uio/Kconfig
> >> @@ -74,6 +74,14 @@ config UIO_SERCOS3
> >>
> >>         If you compile this as a module, it will be called uio_sercos3.
> >>
> >> +config UIO_IVSHMEM
> >> +     tristate "KVM shared memory PCI driver"
> >> +     default n
> >> +     help
> >> +       Userspace I/O interface for the KVM shared memory device.  This
> >> +       driver will make available two memory regions, the first is
> >> +       registers and the second is a region for sharing between VMs.
> >> +
> >>  config UIO_PCI_GENERIC
> >>       tristate "Generic driver for PCI 2.3 and PCI Express cards"
> >>       depends on PCI
> >> diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
> >> index 18fd818..25c1ca5 100644
> >> --- a/drivers/uio/Makefile
> >> +++ b/drivers/uio/Makefile
> >> @@ -6,3 +6,4 @@ obj-$(CONFIG_UIO_AEC) += uio_aec.o
> >>  obj-$(CONFIG_UIO_SERCOS3)    += uio_sercos3.o
> >>  obj-$(CONFIG_UIO_PCI_GENERIC)        += uio_pci_generic.o
> >>  obj-$(CONFIG_UIO_NETX)       += uio_netx.o
> >> +obj-$(CONFIG_UIO_IVSHMEM) += uio_ivshmem.o
> >> diff --git a/drivers/uio/uio_ivshmem.c b/drivers/uio/uio_ivshmem.c
> >> new file mode 100644
> >> index 0000000..607435b
> >> --- /dev/null
> >> +++ b/drivers/uio/uio_ivshmem.c
> >> @@ -0,0 +1,235 @@
> >> +/*
> >> + * UIO IVShmem Driver
> >> + *
> >> + * (C) 2009 Cam Macdonell
> >> + * based on Hilscher CIF card driver (C) 2007 Hans J. Koch <hjk@linutronix.de>
> >> + *
> >> + * Licensed under GPL version 2 only.
> >> + *
> >> + */
> >> +
> >> +#include <linux/device.h>
> >> +#include <linux/module.h>
> >> +#include <linux/pci.h>
> >> +#include <linux/uio_driver.h>
> >> +
> >> +#include <asm/io.h>
> >> +
> >> +#define IntrStatus 0x04
> >> +#define IntrMask 0x00
> >> +
> >> +struct ivshmem_info {
> >> +    struct uio_info *uio;
> >> +    struct pci_dev *dev;
> >> +    char (*msix_names)[256];
> >> +    struct msix_entry *msix_entries;
> >> +    int nvectors;
> >> +};
> >> +
> >> +static irqreturn_t ivshmem_handler(int irq, struct uio_info *dev_info)
> >> +{
> >> +
> >> +    void __iomem *plx_intscr = dev_info->mem[0].internal_addr
> >> +                    + IntrStatus;
> >> +    u32 val;
> >> +
> >> +    val = readl(plx_intscr);
> >> +    if (val == 0)
> >> +        return IRQ_NONE;
> >> +
> >> +    printk(KERN_INFO "Regular interrupt (val = %d)\n", val);
> >> +    return IRQ_HANDLED;
> >> +}
> >> +
> >> +static irqreturn_t ivshmem_msix_handler(int irq, void *opaque)
> >> +{
> >> +
> >> +    struct uio_info * dev_info = (struct uio_info *) opaque;
> >> +
> >> +    /* we have to do this explicitly when using MSI-X */
> >> +    uio_event_notify(dev_info);
> >
> > How does userspace know which vector was triggered?
> 
> Right now, it doesn't.  If a user had a particular need they would
> need to write their own uio driver.  I guess this leads to a
> discussion of MSI support in UIO and how they would work with the
> userspace.

So why request more than one vector then?

> >
> >> +    printk(KERN_INFO "MSI-X interrupt (%d)\n", irq);
> >> +    return IRQ_HANDLED;
> >> +
> >
> > extra empty line
> >
> >> +}
> >> +
> >> +static int request_msix_vectors(struct ivshmem_info *ivs_info, int nvectors)
> >> +{
> >> +    int i, err;
> >> +    const char *name = "ivshmem";
> >> +
> >> +    printk(KERN_INFO "devname is %s\n", name);
> >
> > These KERN_INFO messages need to be cleaned up, they would be
> > look confusing in the log.
> 
> Agreed.  I will clean most of these out.
> 
> >
> >> +    ivs_info->nvectors = nvectors;
> >> +
> >> +
> >> +    ivs_info->msix_entries = kmalloc(nvectors * sizeof *ivs_info->msix_entries,
> >> +            GFP_KERNEL);
> >> +    ivs_info->msix_names = kmalloc(nvectors * sizeof *ivs_info->msix_names,
> >> +            GFP_KERNEL);
> >> +
> >
> > need to handle errors
> >
> >> +    for (i = 0; i < nvectors; ++i)
> >> +        ivs_info->msix_entries[i].entry = i;
> >> +
> >> +    err = pci_enable_msix(ivs_info->dev, ivs_info->msix_entries,
> >> +                    ivs_info->nvectors);
> >> +    if (err > 0) {
> >> +        ivs_info->nvectors = err; /* msi-x positive error code
> >> +                                     returns the number available*/
> >> +        err = pci_enable_msix(ivs_info->dev, ivs_info->msix_entries,
> >> +                    ivs_info->nvectors);
> >> +        if (err > 0) {
> >> +            printk(KERN_INFO "no MSI (%d). Back to INTx.\n", err);
> >> +            return -ENOSPC;
> >> +        }
> >> +    }
> >
> > we can also get err < 0.
> >
> >> +
> >> +    printk(KERN_INFO "err is %d\n", err);
> >> +    if (err) return err;
> >
> > coding style rule violation
> >
> >> +
> >> +    for (i = 0; i < ivs_info->nvectors; i++) {
> >> +
> >> +        snprintf(ivs_info->msix_names[i], sizeof *ivs_info->msix_names,
> >> +            "%s-config", name);
> >> +
> >> +        ivs_info->msix_entries[i].entry = i;
> >> +        err = request_irq(ivs_info->msix_entries[i].vector,
> >> +            ivshmem_msix_handler, 0,
> >> +            ivs_info->msix_names[i], ivs_info->uio);
> >> +
> >> +        if (err) {
> >> +            return -ENOSPC;
> >
> > coding style rule violation
> > no undo on error handling
> > why override error code with -ENOSPC?
> 
> Ah, I think I've confused linux and qemu coding styles perhaps.  I'll
> fix these and others above.
> 
> >
> >> +        }
> >> +    }
> >> +
> >> +    return 0;
> >> +}
> >> +
> >> +static int __devinit ivshmem_pci_probe(struct pci_dev *dev,
> >> +                    const struct pci_device_id *id)
> >> +{
> >> +    struct uio_info *info;
> >> +    struct ivshmem_info * ivshmem_info;
> >> +    int nvectors = 4;
> >> +
> >> +    info = kzalloc(sizeof(struct uio_info), GFP_KERNEL);
> >> +    if (!info)
> >> +        return -ENOMEM;
> >> +
> >> +    ivshmem_info = kzalloc(sizeof(struct ivshmem_info), GFP_KERNEL);
> >> +    if (!ivshmem_info) {
> >> +        kfree(info);
> >> +        return -ENOMEM;
> >> +    }
> >> +
> >> +    if (pci_enable_device(dev))
> >> +        goto out_free;
> >> +
> >> +    if (pci_request_regions(dev, "ivshmem"))
> >> +        goto out_disable;
> >> +
> >> +    info->mem[0].addr = pci_resource_start(dev, 0);
> >> +    if (!info->mem[0].addr)
> >> +        goto out_release;
> >> +
> >> +    info->mem[0].size = pci_resource_len(dev, 0);
> >> +    info->mem[0].internal_addr = pci_ioremap_bar(dev, 0);
> >> +    if (!info->mem[0].internal_addr) {
> >> +        printk(KERN_INFO "got a null");
> >> +        goto out_release;
> >> +    }
> >> +
> >> +    info->mem[0].memtype = UIO_MEM_PHYS;
> >> +
> >> +    info->mem[1].addr = pci_resource_start(dev, 2);
> >> +    if (!info->mem[1].addr)
> >> +        goto out_unmap;
> >> +    info->mem[1].internal_addr = pci_ioremap_bar(dev, 2);
> >> +    if (!info->mem[1].internal_addr)
> >> +        goto out_unmap;
> >> +
> >> +    info->mem[1].size = pci_resource_len(dev, 2);
> >> +    info->mem[1].memtype = UIO_MEM_PHYS;
> >> +
> >> +    ivshmem_info->uio = info;
> >> +    ivshmem_info->dev = dev;
> >> +
> >> +    if (request_msix_vectors(ivshmem_info, nvectors) != 0) {
> >> +        printk(KERN_INFO "regular IRQs\n");
> >> +        info->irq = dev->irq;
> >> +        info->irq_flags = IRQF_SHARED;
> >> +        info->handler = ivshmem_handler;
> >> +        writel(0xffffffff, info->mem[0].internal_addr + IntrMask);
> >> +    } else {
> >> +        printk(KERN_INFO "MSI-X enabled\n");
> >> +        info->irq = -1;
> >> +    }
> >> +
> >> +    info->name = "ivshmem";
> >> +    info->version = "0.0.1";
> >> +
> >> +    if (uio_register_device(&dev->dev, info))
> >> +        goto out_unmap2;
> >> +
> >> +    pci_set_drvdata(dev, info);
> >> +
> >> +
> >> +    return 0;
> >> +out_unmap2:
> >> +    iounmap(info->mem[2].internal_addr);
> >> +out_unmap:
> >> +    iounmap(info->mem[0].internal_addr);
> >> +out_release:
> >> +    pci_release_regions(dev);
> >> +out_disable:
> >> +    pci_disable_device(dev);
> >> +out_free:
> >> +    kfree (info);
> >> +    return -ENODEV;
> >> +}
> >> +
> >> +static void ivshmem_pci_remove(struct pci_dev *dev)
> >> +{
> >> +    struct uio_info *info = pci_get_drvdata(dev);
> >> +
> >> +    uio_unregister_device(info);
> >> +    pci_release_regions(dev);
> >> +    pci_disable_device(dev);
> >> +    pci_set_drvdata(dev, NULL);
> >> +    iounmap(info->mem[0].internal_addr);
> >> +
> >> +    kfree (info);
> >> +}
> >> +
> >> +static struct pci_device_id ivshmem_pci_ids[] __devinitdata = {
> >> +    {
> >> +        .vendor =    0x1af4,
> >> +        .device =    0x1110,
> >
> > vendor ids must be registered with PCI SIG.
> > this one does not seem to be registered.
> >
> >> +        .subvendor =    PCI_ANY_ID,
> >> +        .subdevice =    PCI_ANY_ID,
> >> +    },
> >> +    { 0, }
> >> +};
> >> +
> >> +static struct pci_driver ivshmem_pci_driver = {
> >> +    .name = "uio_ivshmem",
> >> +    .id_table = ivshmem_pci_ids,
> >> +    .probe = ivshmem_pci_probe,
> >> +    .remove = ivshmem_pci_remove,
> >> +};
> >> +
> >> +static int __init ivshmem_init_module(void)
> >> +{
> >> +    return pci_register_driver(&ivshmem_pci_driver);
> >> +}
> >> +
> >> +static void __exit ivshmem_exit_module(void)
> >> +{
> >> +    pci_unregister_driver(&ivshmem_pci_driver);
> >> +}
> >> +
> >> +module_init(ivshmem_init_module);
> >> +module_exit(ivshmem_exit_module);
> >> +
> >> +MODULE_DEVICE_TABLE(pci, ivshmem_pci_ids);
> >> +MODULE_LICENSE("GPL v2");
> >> +MODULE_AUTHOR("Cam Macdonell");
> >> --
> >> 1.6.6.1
> >>
> >> --
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> >
> >