| Message ID | 20220719121523.21396-3-abhsahu@nvidia.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | vfio/pci: power management changes | expand |
On Tue, 19 Jul 2022 17:45:20 +0530 Abhishek Sahu <abhsahu@nvidia.com> wrote: > The vfio-pci based drivers will have runtime power management > support where the user can put the device into the low power state > and then PCI devices can go into the D3cold state. If the device is > in the low power state and the user issues any IOCTL, then the > device should be moved out of the low power state first. Once > the IOCTL is serviced, then it can go into the 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. In the vfio-pci drivers also, > the variant drivers can opt-out by incrementing the usage count during > device-open. The pm_runtime_resume_and_get() checks the device > current status and will return early if the device is already in the > ACTIVE state. > > Taking this usage count incremented while servicing IOCTL will make > sure that the user won't put the device into the low power state when any > other IOCTL is being serviced in parallel. Let's consider the > following scenario: > > 1. Some other IOCTL is called. > 2. The user has opened another device instance and called the IOCTL for > low power entry. > 3. The low power entry IOCTL moves the device into the low power state. > 4. The other IOCTL finishes. > > If we don't keep the usage count incremented then the device > access will happen between step 3 and 4 while the device has already > gone into the low power state. > > The pm_runtime_resume_and_get() will be the first call so its error > should not be propagated to user space directly. For example, if > pm_runtime_resume_and_get() can return -EINVAL for the cases where the > user has passed the correct argument. So the > pm_runtime_resume_and_get() errors have been masked behind -EIO. > > Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com> > --- > drivers/vfio/vfio.c | 52 ++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 49 insertions(+), 3 deletions(-) > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > index bd84ca7c5e35..1d005a0a9d3d 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" > @@ -1335,6 +1336,39 @@ static const struct file_operations vfio_group_fops = { > .release = vfio_group_fops_release, > }; > > +/* > + * Wrapper around pm_runtime_resume_and_get(). > + * Return error code on failure or 0 on success. > + */ > +static inline int vfio_device_pm_runtime_get(struct vfio_device *device) > +{ > + struct device *dev = device->dev; > + > + if (dev->driver && dev->driver->pm) { > + int ret; > + > + ret = pm_runtime_resume_and_get(dev); > + if (ret < 0) { Nit, pm_runtime_resume_and_get() cannot return a positive value, it's either zero or -errno, so we could just test (ret). Thanks, Alex > + dev_info_ratelimited(dev, > + "vfio: runtime resume failed %d\n", ret); > + return -EIO; > + } > + } > + > + return 0; > +} > + > +/* > + * Wrapper around pm_runtime_put(). > + */ > +static inline void vfio_device_pm_runtime_put(struct vfio_device *device) > +{ > + struct device *dev = device->dev; > + > + if (dev->driver && dev->driver->pm) > + pm_runtime_put(dev); > +} > + > /* > * VFIO Device fd > */ > @@ -1649,15 +1683,27 @@ static long vfio_device_fops_unl_ioctl(struct file *filep, > unsigned int cmd, unsigned long arg) > { > struct vfio_device *device = filep->private_data; > + int ret; > + > + ret = vfio_device_pm_runtime_get(device); > + if (ret) > + return ret; > > 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; > } > + > + vfio_device_pm_runtime_put(device); > + return ret; > } > > static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf,
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index bd84ca7c5e35..1d005a0a9d3d 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" @@ -1335,6 +1336,39 @@ static const struct file_operations vfio_group_fops = { .release = vfio_group_fops_release, }; +/* + * Wrapper around pm_runtime_resume_and_get(). + * Return error code on failure or 0 on success. + */ +static inline int vfio_device_pm_runtime_get(struct vfio_device *device) +{ + struct device *dev = device->dev; + + if (dev->driver && dev->driver->pm) { + int ret; + + ret = pm_runtime_resume_and_get(dev); + if (ret < 0) { + dev_info_ratelimited(dev, + "vfio: runtime resume failed %d\n", ret); + return -EIO; + } + } + + return 0; +} + +/* + * Wrapper around pm_runtime_put(). + */ +static inline void vfio_device_pm_runtime_put(struct vfio_device *device) +{ + struct device *dev = device->dev; + + if (dev->driver && dev->driver->pm) + pm_runtime_put(dev); +} + /* * VFIO Device fd */ @@ -1649,15 +1683,27 @@ static long vfio_device_fops_unl_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) { struct vfio_device *device = filep->private_data; + int ret; + + ret = vfio_device_pm_runtime_get(device); + if (ret) + return ret; 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; } + + vfio_device_pm_runtime_put(device); + return ret; } static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf,
The vfio-pci based drivers will have runtime power management support where the user can put the device into the low power state and then PCI devices can go into the D3cold state. If the device is in the low power state and the user issues any IOCTL, then the device should be moved out of the low power state first. Once the IOCTL is serviced, then it can go into the 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. In the vfio-pci drivers also, the variant drivers can opt-out by incrementing the usage count during device-open. The pm_runtime_resume_and_get() checks the device current status and will return early if the device is already in the ACTIVE state. Taking this usage count incremented while servicing IOCTL will make sure that the user won't put the device into the low power state when any other IOCTL is being serviced in parallel. Let's consider the following scenario: 1. Some other IOCTL is called. 2. The user has opened another device instance and called the IOCTL for low power entry. 3. The low power entry IOCTL moves the device into the low power state. 4. The other IOCTL finishes. If we don't keep the usage count incremented then the device access will happen between step 3 and 4 while the device has already gone into the low power state. The pm_runtime_resume_and_get() will be the first call so its error should not be propagated to user space directly. For example, if pm_runtime_resume_and_get() can return -EINVAL for the cases where the user has passed the correct argument. So the pm_runtime_resume_and_get() errors have been masked behind -EIO. Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com> --- drivers/vfio/vfio.c | 52 ++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 49 insertions(+), 3 deletions(-)