linux-kernel - Re: [PATCH V9 6/9] vfio: platform: call

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Message-ID: <20160714160439.5bafca73@t450s.home>
Date:	Thu, 14 Jul 2016 16:04:39 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Sinan Kaya <okaya@...eaurora.org>
Cc:	kvm@...r.kernel.org, timur@...eaurora.org, cov@...eaurora.org,
	jcm@...hat.com, eric.auger@...hat.com, linux-acpi@...r.kernel.org,
	agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V9 6/9] vfio: platform: call _RST method when using ACPI

On Wed, 13 Jul 2016 22:06:32 -0400
Sinan Kaya <okaya@...eaurora.org> wrote:

> The device tree code checks for the presence of a reset driver and calls
> the of_reset function pointer by looking up the reset driver as a module.
> 
> ACPI defines _RST method to perform device level reset. After the _RST
> method is executed, the OS can resume using the device. _RST method is
> expected to stop DMA transfers and IRQs.
> 
> This patch introduces two functions as vfio_platform_acpi_has_reset and
> vfio_platform_acpi_call_reset. The has reset method is used to declare
> reset capability via the ioctl flag VFIO_DEVICE_FLAGS_RESET. The call
> reset function is used to execute the _RST ACPI method.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  drivers/vfio/platform/vfio_platform_common.c | 52 +++++++++++++++++++++++++++-
>  1 file changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index 03483c2..2d9c905 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -28,6 +28,8 @@
>  #define DRIVER_AUTHOR   "Antonios Motakis <a.motakis@...tualopensystems.com>"
>  #define DRIVER_DESC     "VFIO platform base module"
>  
> +#define VFIO_PLATFORM_IS_ACPI(vdev) ((vdev)->acpihid != NULL)
> +
>  static LIST_HEAD(reset_list);
>  static DEFINE_MUTEX(driver_lock);
>  
> @@ -77,13 +79,55 @@ static int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
>  #endif
>  }
>  
> +static inline
> +int vfio_platform_acpi_call_reset(struct vfio_platform_device *vdev,
> +				  const char **extra_dbg)
> +{
> +#ifdef CONFIG_ACPI
> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +	struct device *dev = vdev->device;
> +	acpi_handle handle = ACPI_HANDLE(dev);
> +	acpi_status acpi_ret;
> +
> +	acpi_ret = acpi_evaluate_object(handle, "_RST", NULL, &buffer);
> +	if (ACPI_FAILURE(acpi_ret)) {
> +		if (extra_dbg)
> +			*extra_dbg = acpi_format_exception(acpi_ret);
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +#else
> +	return -ENOENT;
> +#endif
> +}
> +
> +static inline
> +bool vfio_platform_acpi_has_reset(struct vfio_platform_device *vdev)
> +{
> +#ifdef CONFIG_ACPI
> +	struct device *dev = vdev->device;
> +	acpi_handle handle = ACPI_HANDLE(dev);
> +
> +	return acpi_has_method(handle, "_RST");
> +#else
> +	return false;
> +#endif
> +}

What exactly is the rationale for making these inline?  Clearly reset
is not a performance relevant path.  Thanks,

Alex

> +
>  static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
>  {
> +	if (VFIO_PLATFORM_IS_ACPI(vdev))
> +		return vfio_platform_acpi_has_reset(vdev);
> +
>  	return vdev->of_reset ? true : false;
>  }
>  
>  static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
>  {
> +	if (VFIO_PLATFORM_IS_ACPI(vdev))
> +		return;
> +
>  	vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
>  						    &vdev->reset_module);
>  	if (!vdev->of_reset) {
> @@ -95,6 +139,9 @@ static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
>  
>  static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
>  {
> +	if (VFIO_PLATFORM_IS_ACPI(vdev))
> +		return;
> +
>  	if (vdev->of_reset)
>  		module_put(vdev->reset_module);
>  }
> @@ -170,7 +217,10 @@ static void vfio_platform_regions_cleanup(struct vfio_platform_device *vdev)
>  static int vfio_platform_call_reset(struct vfio_platform_device *vdev,
>  				    const char **extra_dbg)
>  {
> -	if (vdev->of_reset) {
> +	if (VFIO_PLATFORM_IS_ACPI(vdev)) {
> +		dev_info(vdev->device, "reset\n");
> +		return vfio_platform_acpi_call_reset(vdev, extra_dbg);
> +	} else if (vdev->of_reset) {
>  		dev_info(vdev->device, "reset\n");
>  		return vdev->of_reset(vdev);
>  	}