On 5/5/2022 1:12 AM, Alex Williamson wrote: > On Mon, 25 Apr 2022 14:56:13 +0530 > Abhishek Sahu <abhsahu@xxxxxxxxxx> wrote: > >> The vfio/pci driver will have runtime power management support where the >> user can put the device low power state and then PCI devices can go into >> the D3cold state. If the device is in low power state and user issues any >> IOCTL, then the device should be moved out of low power state first. Once >> the IOCTL is serviced, then it can go into low power state again. The >> runtime PM framework manages this with help of usage count. One option >> was to add the runtime PM related API's inside vfio/pci driver but some >> IOCTL (like VFIO_DEVICE_FEATURE) can follow a different path and more >> IOCTL can be added in the future. Also, the runtime PM will be >> added for vfio/pci based drivers variant currently but the other vfio >> based drivers can use the same in the future. So, this patch adds the >> runtime calls runtime related API in the top level IOCTL function itself. >> >> For the vfio drivers which do not have runtime power management support >> currently, the runtime PM API's won't be invoked. Only for vfio/pci >> based drivers currently, the runtime PM API's will be invoked to increment >> and decrement the usage count. Taking this usage count incremented while >> servicing IOCTL will make sure that user won't put the device into low >> power state when any other IOCTL is being serviced in parallel. >> >> Signed-off-by: Abhishek Sahu <abhsahu@xxxxxxxxxx> >> --- >> drivers/vfio/vfio.c | 44 +++++++++++++++++++++++++++++++++++++++++--- >> 1 file changed, 41 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c >> index a4555014bd1e..4e65a127744e 100644 >> --- a/drivers/vfio/vfio.c >> +++ b/drivers/vfio/vfio.c >> @@ -32,6 +32,7 @@ >> #include <linux/vfio.h> >> #include <linux/wait.h> >> #include <linux/sched/signal.h> >> +#include <linux/pm_runtime.h> >> #include "vfio.h" >> >> #define DRIVER_VERSION "0.3" >> @@ -1536,6 +1537,30 @@ static const struct file_operations vfio_group_fops = { >> .release = vfio_group_fops_release, >> }; >> >> +/* >> + * Wrapper around pm_runtime_resume_and_get(). >> + * Return 0, if driver power management callbacks are not present i.e. the driver is not > > Mind the gratuitous long comment line here. > Thanks Alex. That was a miss. I will fix this. >> + * using runtime power management. >> + * Return 1 upon success, otherwise -errno > > Changing semantics vs the thing we're wrapping, why not provide a > wrapper for the `put` as well to avoid? The only cases where we return > zero are just as easy to detect on the other side. > Yes. Using wrapper function for put is better option. I will make the changes. >> + */ >> +static inline int vfio_device_pm_runtime_get(struct device *dev) > > Given some of Jason's recent series, this should probably just accept a > vfio_device. > Sorry. I didn't get this part. Do I need to change it to static inline int vfio_device_pm_runtime_get(struct vfio_device *device) { struct device *dev = device->dev; ... } >> +{ >> +#ifdef CONFIG_PM >> + int ret; >> + >> + if (!dev->driver || !dev->driver->pm) >> + return 0; >> + >> + ret = pm_runtime_resume_and_get(dev); >> + if (ret < 0) >> + return ret; >> + >> + return 1; >> +#else >> + return 0; >> +#endif >> +} >> + >> /* >> * VFIO Device fd >> */ >> @@ -1845,15 +1870,28 @@ static long vfio_device_fops_unl_ioctl(struct file *filep, >> unsigned int cmd, unsigned long arg) >> { >> struct vfio_device *device = filep->private_data; >> + int pm_ret, ret = 0; >> + >> + pm_ret = vfio_device_pm_runtime_get(device->dev); >> + if (pm_ret < 0) >> + return pm_ret; > > I wonder if we might simply want to mask pm errors behind -EIO, maybe > with a rate limited dev_info(). My concern would be that we might mask > errnos that userspace has come to expect for certain ioctls. Thanks, > > Alex > I need to do something like following. Correct ? ret = vfio_device_pm_runtime_get(device); if (ret < 0) { dev_info_ratelimited(device->dev, "vfio: runtime resume failed %d\n", ret); return -EIO; } Regards, Abhishek >> >> switch (cmd) { >> case VFIO_DEVICE_FEATURE: >> - return vfio_ioctl_device_feature(device, (void __user *)arg); >> + ret = vfio_ioctl_device_feature(device, (void __user *)arg); >> + break; >> default: >> if (unlikely(!device->ops->ioctl)) >> - return -EINVAL; >> - return device->ops->ioctl(device, cmd, arg); >> + ret = -EINVAL; >> + else >> + ret = device->ops->ioctl(device, cmd, arg); >> + break; >> } >> + >> + if (pm_ret) >> + pm_runtime_put(device->dev); >> + >> + return ret; >> } >> >> static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf, >