Re: [v2 24/31] drm/xe/svm: Create and destroy xe svm

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Apr 09, 2024 at 04:17:35PM -0400, Oak Zeng wrote:
> Introduce a data structure xe_svm to represent a shared virtual
> address space b/t CPU program and GPU program. Each process can
> only have maximumly one xe_svm instance. One xe_svm can have
> multiple gpu vm.
> 
> Introduce helper functions to create and destroy xe_svm instance.
> Once xe_svm instance is created, it is added to a global hash table
> keyed by mm_struct. Later on we can retrieve xe_svm using mm_struct.
> 

I don't think this needed at all, will explain a bit later in the series
but quite sure this can be droppped entirely.

Matt

> Signed-off-by: Oak Zeng <oak.zeng@intel.com>
> ---
>  drivers/gpu/drm/xe/Makefile |  1 +
>  drivers/gpu/drm/xe/xe_svm.c | 77 +++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_svm.h | 23 +++++++++++
>  3 files changed, 101 insertions(+)
>  create mode 100644 drivers/gpu/drm/xe/xe_svm.c
> 
> diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> index cd5213ba182b..f89d77b6d654 100644
> --- a/drivers/gpu/drm/xe/Makefile
> +++ b/drivers/gpu/drm/xe/Makefile
> @@ -129,6 +129,7 @@ xe-y += xe_bb.o \
>  	xe_sa.o \
>  	xe_sched_job.o \
>  	xe_step.o \
> +	xe_svm.o \
>  	xe_svm_devmem.o \
>  	xe_sync.o \
>  	xe_tile.o \
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> new file mode 100644
> index 000000000000..416cfc81c053
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -0,0 +1,77 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2023 Intel Corporation
> + */
> +
> +#include <linux/mutex.h>
> +#include <linux/mm_types.h>
> +#include <linux/kernel.h>
> +#include <linux/hashtable.h>
> +#include "xe_svm.h"
> +
> +#define XE_MAX_SVM_PROCESS 5 /* Maximumly support 32 SVM process*/
> +DEFINE_HASHTABLE(xe_svm_table, XE_MAX_SVM_PROCESS);
> +
> +/**
> + * xe_create_svm() - create a svm instance
> + *
> + * one xe_svm struct represent a shared address space
> + * between cpu and gpu program. So one xe_svm is associated
> + * to one mm_struct.
> + *
> + * If xe_svm for this process already exists, just return
> + * it; otherwise create one.
> + *
> + * Return the created xe svm struct pointer
> + */
> +struct xe_svm *xe_create_svm(void)
> +{
> +	struct mm_struct *mm = current->mm;
> +	struct xe_svm *svm;
> +
> +	svm = xe_lookup_svm_by_mm(mm);
> +	if (svm)
> +		return svm;
> +
> +	svm = kzalloc(sizeof(struct xe_svm), GFP_KERNEL);
> +	svm->mm = mm;
> +	mutex_init(&svm->mutex);
> +	INIT_LIST_HEAD(&svm->vm_list);
> +	/** Add svm to global xe_svm_table hash table
> +	 *  use mm as key so later we can retrieve svm using mm
> +	 */
> +	hash_add_rcu(xe_svm_table, &svm->hnode, (uintptr_t)mm);
> +	return svm;
> +}
> +
> +/**
> + * xe_destroy_svm() - destroy a svm process
> + *
> + * @svm: the xe_svm to destroy
> + */
> +void xe_destroy_svm(struct xe_svm *svm)
> +{
> +	BUG_ON(list_empty(&svm->vm_list));
> +	hash_del_rcu(&svm->hnode);
> +	mutex_destroy(&svm->mutex);
> +	kfree(svm);
> +}
> +
> +
> +/**
> + * xe_lookup_svm_by_mm() - retrieve xe_svm from mm struct
> + *
> + * @mm: the mm struct of the svm to retrieve
> + *
> + * Return the xe_svm struct pointer, or NULL if fail
> + */
> +struct xe_svm *xe_lookup_svm_by_mm(struct mm_struct *mm)
> +{
> +	struct xe_svm *svm;
> +
> +	hash_for_each_possible_rcu(xe_svm_table, svm, hnode, (uintptr_t)mm)
> +		if (svm->mm == mm)
> +			return svm;
> +
> +	return NULL;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
> index 92a3ee90d5a7..066740fb93f5 100644
> --- a/drivers/gpu/drm/xe/xe_svm.h
> +++ b/drivers/gpu/drm/xe/xe_svm.h
> @@ -11,6 +11,29 @@
>  #include "xe_device.h"
>  #include "xe_assert.h"
>  
> +
> +/**
> + * struct xe_svm - data structure to represent a shared
> + * virtual address space from device side. xe_svm and
> + * mm_struct has a 1:1 relationship.
> + */
> +struct xe_svm {
> +	/** @mm: The mm_struct corresponding to this xe_svm */
> +	struct mm_struct *mm;
> +	/**
> +	 * @mutex: A lock protects below vm_list
> +	 */
> +	struct mutex mutex;
> +	/** @hnode: used to add this svm to a global xe_svm_hash table*/
> +	struct hlist_node hnode;
> +	/** @vm_list: a list gpu vm in this svm space */
> +	struct list_head vm_list;
> +};
> +
> +extern struct xe_svm *xe_create_svm(void);
> +void xe_destroy_svm(struct xe_svm *svm);
> +extern struct xe_svm *xe_lookup_svm_by_mm(struct mm_struct *mm);
> +
>  /**
>   * xe_mem_region_pfn_to_dpa() - Calculate page's dpa from pfn
>   *
> -- 
> 2.26.3
>