Re: [PATCH v8 6/6] drm/xe/xe_vm: Implement xe_vm_get_property_ioctl

[Jianxun Zhang <jianxun.zhang@intel.com>]

On 3/13/25 11:34, Jonathan Cavitt wrote:
> Add support for userspace to request a list of observed faults
> from a specified VM.
> 
> v2:
> - Only allow querying of failed pagefaults (Matt Brost)
> 
> v3:
> - Remove unnecessary size parameter from helper function, as it
>    is a property of the arguments. (jcavitt)
> - Remove unnecessary copy_from_user (Jainxun)
> - Set address_precision to 1 (Jainxun)
> - Report max size instead of dynamic size for memory allocation
>    purposes.  Total memory usage is reported separately.
> 
> v4:
> - Return int from xe_vm_get_property_size (Shuicheng)
> - Fix memory leak (Shuicheng)
> - Remove unnecessary size variable (jcavitt)
> 
> v5:
> - Rename ioctl to xe_vm_get_faults_ioctl (jcavitt)
> - Update fill_property_pfs to eliminate need for kzalloc (Jianxun)
> 
> v6:
> - Repair and move fill_faults break condition (Dan Carpenter)
> - Free vm after use (jcavitt)
> - Combine assertions (jcavitt)
> - Expand size check in xe_vm_get_faults_ioctl (jcavitt)
> - Remove return mask from fill_faults, as return is already -EFAULT or 0
>    (jcavitt)
> 
> v7:
> - Revert back to using xe_vm_get_property_ioctl
> - Apply better copy_to_user logic (jcavitt)
> 
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
> Suggested-by: Matthew Brost <matthew.brost@intel.com>
> Cc: Jainxun Zhang <jianxun.zhang@intel.com>
> Cc: Shuicheng Lin <shuicheng.lin@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_device.c |   3 +
>   drivers/gpu/drm/xe/xe_vm.c     | 134 +++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/xe/xe_vm.h     |   2 +
>   3 files changed, 139 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index b2f656b2a563..74e510cb0e47 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -194,6 +194,9 @@ static const struct drm_ioctl_desc xe_ioctls[] = {
>   	DRM_IOCTL_DEF_DRV(XE_WAIT_USER_FENCE, xe_wait_user_fence_ioctl,
>   			  DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF_DRV(XE_OBSERVATION, xe_observation_ioctl, DRM_RENDER_ALLOW),
> +	DRM_IOCTL_DEF_DRV(XE_VM_GET_PROPERTY, xe_vm_get_property_ioctl,
> +			  DRM_RENDER_ALLOW),
> +
>   };
>   
>   static long xe_drm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 067a9cedcad9..521f0032d9e2 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -42,6 +42,14 @@
>   #include "xe_wa.h"
>   #include "xe_hmm.h"
>   
> +static const u16 xe_to_user_engine_class[] = {
> +	[XE_ENGINE_CLASS_RENDER] = DRM_XE_ENGINE_CLASS_RENDER,
> +	[XE_ENGINE_CLASS_COPY] = DRM_XE_ENGINE_CLASS_COPY,
> +	[XE_ENGINE_CLASS_VIDEO_DECODE] = DRM_XE_ENGINE_CLASS_VIDEO_DECODE,
> +	[XE_ENGINE_CLASS_VIDEO_ENHANCE] = DRM_XE_ENGINE_CLASS_VIDEO_ENHANCE,
> +	[XE_ENGINE_CLASS_COMPUTE] = DRM_XE_ENGINE_CLASS_COMPUTE,
> +};
> +
>   static struct drm_gem_object *xe_vm_obj(struct xe_vm *vm)
>   {
>   	return vm->gpuvm.r_obj;
> @@ -3551,6 +3559,132 @@ int xe_vm_bind_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
>   	return err;
>   }
>   
> +static int xe_vm_get_property_size(struct xe_vm *vm, u32 property)
> +{
> +	int size = -EINVAL;
> +
> +	switch (property) {
> +	case DRM_XE_VM_GET_PROPERTY_FAULTS:
> +		spin_lock(&vm->faults.lock);
> +		size = vm->faults.len * sizeof(struct xe_vm_fault);
> +		spin_unlock(&vm->faults.lock);
> +		break;
> +	default:
> +		break;
> +	}
> +	return size;
> +}
> +
> +static int xe_vm_get_property_verify_size(struct xe_vm *vm, u32 property,
> +					  int expected, int actual)
> +{
> +	switch (property) {
> +	case DRM_XE_VM_GET_PROPERTY_FAULTS:
> +		/*
> +		 * Number of faults may increase between calls to
> +		 * xe_vm_get_property_ioctl, so just report the
> +		 * number of faults the user requests if it's less
> +		 * than or equal to the number of faults in the VM
> +		 * fault array.
> +		 */
> +		if (actual < expected)
> +			return -EINVAL;
Application should be allowed to provide more memory than the needed. In 
return, the driver should update the arg->size with number of bytes 
actually written to the memory.
> +		break;
> +	default:
> +		if (actual != expected)
> +			return -EINVAL;
> +		break;
> +	}
> +	return 0;
> +}
> +
> +static int fill_faults(struct xe_vm *vm,
> +		       struct drm_xe_vm_get_property *args)
> +{
> +	struct xe_vm_fault __user *usr_ptr = u64_to_user_ptr(args->data);
> +	struct xe_vm_fault store = { 0 };
> +	struct xe_vm_fault_entry *entry;
> +	int ret = 0, i = 0, count;
> +
> +	count = args->size / sizeof(struct xe_vm_fault);
> +
> +	spin_lock(&vm->faults.lock);
> +	list_for_each_entry(entry, &vm->faults.list, list) {
> +		if (i++ == count)
> +			break;
> +
> +		memset(&store, 0, sizeof(struct xe_vm_fault));
> +
> +		store.address = entry->address;
> +		store.address_type = entry->address_type;
> +		store.address_precision = entry->address_precision;
> +		store.fault_level = entry->fault_level;
> +		store.engine_class = xe_to_user_engine_class[entry->engine_class];
> +		store.engine_instance = entry->engine_instance;
> +
> +		ret = copy_to_user(usr_ptr, &store, sizeof(struct xe_vm_fault));
> +		if (ret)
> +			break;
> +
> +		usr_ptr++;
> +	}
> +	spin_unlock(&vm->faults.lock);
> +
Update the args->size with the amount of the written. Refer to my 
another comment above. Also document this in the comment of the interface.
> +	return ret;
> +}
> +
> +static int xe_vm_get_property_fill_data(struct xe_vm *vm,
> +					struct drm_xe_vm_get_property *args)
> +{
> +	switch (args->property) {
> +	case DRM_XE_VM_GET_PROPERTY_FAULTS:
> +		return fill_faults(vm, args);
> +	default:
> +		break;
> +	}
> +	return -EINVAL;
> +}
> +
> +int xe_vm_get_property_ioctl(struct drm_device *drm, void *data,
> +			     struct drm_file *file)
> +{
> +	struct xe_device *xe = to_xe_device(drm);
> +	struct xe_file *xef = to_xe_file(file);
> +	struct drm_xe_vm_get_property *args = data;
> +	struct xe_vm *vm;
> +	int size, ret = 0;
> +
> +	if (XE_IOCTL_DBG(xe, args->reserved[0] || args->reserved[1]))
> +		return -EINVAL;
> +
> +	vm = xe_vm_lookup(xef, args->vm_id);
> +	if (XE_IOCTL_DBG(xe, !vm))
> +		return -ENOENT;
> +
> +	size = xe_vm_get_property_size(vm, args->property);
> +
> +	if (size < 0) {
> +		ret = size;
> +		goto put_vm;
> +	} else if (!args->size) {
> +		args->size = size;
> +		goto put_vm;
> +	}
> +
> +	ret = xe_vm_get_property_verify_size(vm, args->property,
> +					     args->size, size);
> +	if (XE_IOCTL_DBG(xe, ret)) {
> +		ret = -EINVAL;
> +		goto put_vm;
> +	}
> +
> +	ret = xe_vm_get_property_fill_data(vm, args);
> +
> +put_vm:
> +	xe_vm_put(vm);
> +	return ret;
> +}
> +
>   /**
>    * xe_vm_bind_kernel_bo - bind a kernel BO to a VM
>    * @vm: VM to bind the BO to
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index 9bd7e93824da..63ec22458e04 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -196,6 +196,8 @@ int xe_vm_destroy_ioctl(struct drm_device *dev, void *data,
>   			struct drm_file *file);
>   int xe_vm_bind_ioctl(struct drm_device *dev, void *data,
>   		     struct drm_file *file);
> +int xe_vm_get_property_ioctl(struct drm_device *dev, void *data,
> +			     struct drm_file *file);
>   
>   void xe_vm_close_and_put(struct xe_vm *vm);
>