________________________________________
From: Brost, Matthew <matthew.brost@xxxxxxxxx>
Sent: Monday, March 10, 2025 9:50 PM
To: Cavitt, Jonathan
Cc: intel-xe@xxxxxxxxxxxxxxxxxxxxx; Gupta, saurabhg; Zuo, Alex; joonas.lahtinen@xxxxxxxxxxxxxxx; Zhang, Jianxun; Lin, Shuicheng; dri-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH v7 4/6] drm/xe/uapi: Define drm_xe_vm_get_faults
On Mon, Mar 10, 2025 at 05:18:32PM +0000, Jonathan Cavitt wrote:
> Add initial declarations for the drm_xe_vm_get_faults ioctl.
>
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx>
> ---
> include/uapi/drm/xe_drm.h | 49 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 49 insertions(+)
>
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index 616916985e3f..90c2fcdbd5c1 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -81,6 +81,7 @@ extern "C" {
> * - &DRM_IOCTL_XE_EXEC
> * - &DRM_IOCTL_XE_WAIT_USER_FENCE
> * - &DRM_IOCTL_XE_OBSERVATION
> + * - %DRM_IOCTL_XE_VM_GET_FAULTS
This should be a generic "get VM property" IOCTL, not a specific IOCTL
that only retrieves faults. This allows for future expansion of the
uAPI.
> */
>
> /*
> @@ -102,6 +103,7 @@ extern "C" {
> #define DRM_XE_EXEC 0x09
> #define DRM_XE_WAIT_USER_FENCE 0x0a
> #define DRM_XE_OBSERVATION 0x0b
> +#define DRM_XE_VM_GET_FAULTS 0x0c
>
> /* Must be kept compact -- no holes */
>
> @@ -117,6 +119,7 @@ extern "C" {
> #define DRM_IOCTL_XE_EXEC DRM_IOW(DRM_COMMAND_BASE + DRM_XE_EXEC, struct drm_xe_exec)
> #define DRM_IOCTL_XE_WAIT_USER_FENCE DRM_IOWR(DRM_COMMAND_BASE + DRM_XE_WAIT_USER_FENCE, struct drm_xe_wait_user_fence)
> #define DRM_IOCTL_XE_OBSERVATION DRM_IOW(DRM_COMMAND_BASE + DRM_XE_OBSERVATION, struct drm_xe_observation_param)
> +#define DRM_IOCTL_XE_VM_GET_FAULTS DRM_IOWR(DRM_COMMAND_BASE + DRM_XE_VM_GET_FAULTS, struct drm_xe_vm_get_faults)
>
> /**
> * DOC: Xe IOCTL Extensions
> @@ -1189,6 +1192,52 @@ struct drm_xe_vm_bind {
> __u64 reserved[2];
> };
>
> +struct xe_vm_fault {
> + /** @address: Address of the fault, if relevant */
> + __u64 address;
> +#define DRM_XE_FAULT_ADDRESS_TYPE_NONE_EXT 0
> +#define DRM_XE_FAULT_ADDRESS_TYPE_READ_INVALID_EXT 1
> +#define DRM_XE_FAULT_ADDRESS_TYPE_WRITE_INVALID_EXT 2
> + /** @address_type: , if relevant */
> + __u32 address_type;
> + /**
> + * @address_precision: Precision of faulted address, if relevant.
> + * Currently only SZ_4K.
The fault address should be no ambiguity, so I think the precision should be 1 for page fault. Please correct me if I am wrong here.
> + */
> + __u32 address_precision;
As I mentioned in offline discussion, I suggest we add engine class and instance into page fault report. I think it is important to know which engine the fault was from.
> + /** @reserved: MBZ */
> + __u64 reserved[3];
> +};
> +
> +/**
> + * struct drm_xe_vm_get_faults - Input of &DRM_IOCTL_XE_VM_GET_FAULTS
> + *
> + * The user provides a VM ID, and the ioctl will
> + *
> + */
> +struct drm_xe_vm_get_faults {
> + /** @extensions: Pointer to the first extension struct, if any */
> + __u64 extensions;
> +
> + /** @vm_id: The ID of the VM to query the properties of */
> + __u32 vm_id;
> +
> + /** @size: Size to allocate for @ptr */
> + __u32 size;
> +
> + /** @fault_count: Number of faults to be returned */
> + __u32 fault_count;
> +
fault_count is implied by size.
Matt
I think we should remove 'size' and just use fault_count. It is sufficient for user space to calculate the needed size of memory by fault_count and size of xe_vm_fault. In this way it is also better than just using 'size' that causes everywhere to do a dividing op and check the fraction for getting fault_count. Also, the only place to use 'size' is memory allocation. But I can imagine multiple places in UMD and KMD would need fault_count.
> + /** @pad: MBZ */
> + __u32 pad;
> +
> + /** @reserved: MBZ */
> + __u64 reserved[2];
> +
> + /** @faults: Pointer to user-defined array of xe_vm_fault of flexible size */
/** @faults: Pointer to a xe_vm_fault array of fault_count elements provided by user space */
> + __u64 faults;
> +};
> +
> /**
> * struct drm_xe_exec_queue_create - Input of &DRM_IOCTL_XE_EXEC_QUEUE_CREATE
> *
> --
> 2.43.0
>
