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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC PATCH] Xen PCI back - do slot and bus reset (v0).
On Mon, Dec 16, 2013 at 10:59:01AM +0000, David Vrabel wrote:
> On 13/12/13 16:09, Konrad Rzeszutek Wilk wrote:
> > Hey,
> >
> > While I was trying to narrow down the state of GPU passthrough
> > (still not finished) and figuring what needs to be done I realized
> > that Xen PCIback did not reset my GPU properly (when I crashed the
> > Windows guest by mistake). It does an FLR reset or Power one - if
> > the device supports it. But it seems that some of these GPUs
> > are liars and actually don't do the power part properly.
>
> In my experience the devices do not lie. They correctly report that
> they do not perform a reset in D3hot.
>
> Here's the patch I'm using to solve this. It does something similar.
> i.e., a SBR if all devices on that bus are safe to be reset.
>
> I prefer it because it provides the standard 'reset' sysfs file that the
> toolstack/userspace can use.
We can still add the 'reset' to SysFS
>
> It does have some limitations: a) It does not check whether a device is
> in use (only if it is bound to pciback); and b) it hand rolls
> pci_slot_reset() (because it didn't exist at the time).
.. which can have those limiations removed and be based on this patchset.
Meaning it won't do a bus-reset or device reset if the rest of the devices
are _not_ assigned to pciback.
>
> diff --git a/drivers/xen/xen-pciback/pci_stub.c
> b/drivers/xen/xen-pciback/pci_stub.c
> index 4e8ba38..5a03e63 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -14,6 +14,7 @@
> #include <linux/wait.h>
> #include <linux/sched.h>
> #include <linux/atomic.h>
> +#include <linux/delay.h>
> #include <xen/events.h>
> #include <asm/xen/pci.h>
> #include <asm/xen/hypervisor.h>
> @@ -43,6 +44,7 @@ struct pcistub_device {
> struct kref kref;
> struct list_head dev_list;
> spinlock_t lock;
> + bool created_reset_file;
>
> struct pci_dev *dev;
> struct xen_pcibk_device *pdev;/* non-NULL if struct pci_dev is in use */
> @@ -60,6 +62,114 @@ static LIST_HEAD(pcistub_devices);
> static int initialize_devices;
> static LIST_HEAD(seized_devices);
>
> +/*
> + * pci_reset_function() will only work if there is a mechanism to
> + * reset that single function (e.g., FLR or a D-state transition).
> + * For PCI hardware that has two or more functions but no per-function
> + * reset, we can do a bus reset iff all the functions are co-assigned
> + * to the same domain.
> + *
> + * If a function has no per-function reset mechanism the 'reset' sysfs
> + * file that the toolstack uses to reset a function prior to assigning
> + * the device will be missing. In this case, pciback adds its own
> + * which will try a bus reset.
> + *
> + * Note: pciback does not check for co-assigment before doing a bus
> + * reset, only that the devices are bound to pciback. The toolstack
> + * is assumed to have done the right thing.
> + */
> +static int __pcistub_reset_function(struct pci_dev *dev)
> +{
> + struct pci_dev *pdev;
> + u16 ctrl;
> + int ret;
> +
> + ret = __pci_reset_function_locked(dev);
> + if (ret == 0)
> + return 0;
> +
> + if (pci_is_root_bus(dev->bus) || dev->subordinate || !dev->bus->self)
> + return -ENOTTY;
> +
> + list_for_each_entry(pdev, &dev->bus->devices, bus_list) {
> + if (pdev != dev && (!pdev->driver
> + || strcmp(pdev->driver->name, "pciback")))
> + return -ENOTTY;
> + pci_save_state(pdev);
> + }
> +
> + pci_read_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, &ctrl);
> + ctrl |= PCI_BRIDGE_CTL_BUS_RESET;
> + pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl);
> + msleep(200);
> +
> + ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET;
> + pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl);
> + msleep(200);
> +
> + list_for_each_entry(pdev, &dev->bus->devices, bus_list)
> + pci_restore_state(pdev);
> +
> + return 0;
> +}
> +
> +static int pcistub_reset_function(struct pci_dev *dev)
> +{
> + int ret;
> +
> + device_lock(&dev->dev);
> + ret = __pcistub_reset_function(dev);
> + device_unlock(&dev->dev);
> +
> + return ret;
> +}
> +
> +static ssize_t pcistub_reset_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> + unsigned long val;
> + ssize_t result = strict_strtoul(buf, 0, &val);
> +
> + if (result < 0)
> + return result;
> +
> + if (val != 1)
> + return -EINVAL;
> +
> + result = pcistub_reset_function(pdev);
> + if (result < 0)
> + return result;
> + return count;
> +}
> +static DEVICE_ATTR(reset, 0200, NULL, pcistub_reset_store);
> +
> +static int pcistub_try_create_reset_file(struct pcistub_device *psdev)
> +{
> + struct device *dev = &psdev->dev->dev;
> + struct sysfs_dirent *reset_dirent;
> + int ret;
> +
> + reset_dirent = sysfs_get_dirent(dev->kobj.sd, NULL, "reset");
> + if (reset_dirent) {
> + sysfs_put(reset_dirent);
> + return 0;
> + }
> +
> + ret = device_create_file(dev, &dev_attr_reset);
> + if (ret < 0)
> + return ret;
> + psdev->created_reset_file = true;
> + return 0;
> +}
> +
> +static void pcistub_remove_reset_file(struct pcistub_device *psdev)
> +{
> + if (psdev && psdev->created_reset_file)
> + device_remove_file(&psdev->dev->dev, &dev_attr_reset);
> +}
> +
> static struct pcistub_device *pcistub_device_alloc(struct pci_dev *dev)
> {
> struct pcistub_device *psdev;
> @@ -95,12 +205,15 @@ static void pcistub_device_release(struct kref *kref)
>
> dev_dbg(&dev->dev, "pcistub_device_release\n");
>
> + pcistub_remove_reset_file(psdev);
> +
> xen_unregister_device_domain_owner(dev);
>
> /* Call the reset function which does not take lock as this
> * is called from "unbind" which takes a device_lock mutex.
> */
> - __pci_reset_function_locked(dev);
> + __pcistub_reset_function(psdev->dev);
> +
> if (pci_load_and_free_saved_state(dev, &dev_data->pci_saved_state))
> dev_dbg(&dev->dev, "Could not reload PCI state\n");
> else
> @@ -268,7 +381,7 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
> /* This is OK - we are running from workqueue context
> * and want to inhibit the user from fiddling with 'reset'
> */
> - pci_reset_function(dev);
> + pcistub_reset_function(psdev->dev);
> pci_restore_state(psdev->dev);
>
> /* This disables the device. */
> @@ -392,7 +505,7 @@ static int pcistub_init_device(struct pci_dev *dev)
> dev_err(&dev->dev, "Could not store PCI conf saved state!\n");
> else {
> dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");
> - __pci_reset_function_locked(dev);
> + __pcistub_reset_function(dev);
> pci_restore_state(dev);
> }
> /* Now disable the device (this also ensures some private device
> @@ -467,6 +580,10 @@ static int pcistub_seize(struct pci_dev *dev)
> if (!psdev)
> return -ENOMEM;
>
> + err = pcistub_try_create_reset_file(psdev);
> + if (err < 0)
> + goto out;
> +
> spin_lock_irqsave(&pcistub_devices_lock, flags);
>
> if (initialize_devices) {
> @@ -485,10 +602,9 @@ static int pcistub_seize(struct pci_dev *dev)
> }
>
> spin_unlock_irqrestore(&pcistub_devices_lock, flags);
> -
> +out:
> if (err)
> pcistub_device_put(psdev);
> -
> return err;
> }
>
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