Re: [PATCH v4 20/33] drm/xe: Add migrate layer functions for SVM support

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Wed, 2025-01-29 at 11:51 -0800, Matthew Brost wrote:
> Add functions which migrate to / from VRAM accepting a single DPA
> argument (VRAM) and array of dma addresses (SRAM). Used for SVM
> migrations.
> 
> v2:
>  - Don't unlock job_mutex in error path of xe_migrate_vram
> v3:
>  - Kernel doc (Thomas)
>  - Better commit message (Thomas)
>  - s/dword/num_dword (Thomas)
>  - Return error to large of migration (Thomas)
> 
> Signed-off-by: Oak Zeng <oak.zeng@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>


> ---
>  drivers/gpu/drm/xe/xe_migrate.c | 175
> ++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_migrate.h |  10 ++
>  2 files changed, 185 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c
> b/drivers/gpu/drm/xe/xe_migrate.c
> index 278bc96cf593..df4282c71bf0 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -1544,6 +1544,181 @@ void xe_migrate_wait(struct xe_migrate *m)
>  		dma_fence_wait(m->fence, false);
>  }
>  
> +static u32 pte_update_cmd_size(u64 size)
> +{
> +	u32 num_dword;
> +	u64 entries = DIV_ROUND_UP(size, XE_PAGE_SIZE);
> +
> +	XE_WARN_ON(size > MAX_PREEMPTDISABLE_TRANSFER);
> +	/*
> +	 * MI_STORE_DATA_IMM command is used to update page table.
> Each
> +	 * instruction can update maximumly 0x1ff pte entries. To
> update
> +	 * n (n <= 0x1ff) pte entries, we need:
> +	 * 1 dword for the MI_STORE_DATA_IMM command header (opcode
> etc)
> +	 * 2 dword for the page table's physical location
> +	 * 2*n dword for value of pte to fill (each pte entry is 2
> dwords)
> +	 */
> +	num_dword = (1 + 2) * DIV_ROUND_UP(entries, 0x1ff);
> +	num_dword += entries * 2;
> +
> +	return num_dword;
> +}
> +
> +static void build_pt_update_batch_sram(struct xe_migrate *m,
> +				       struct xe_bb *bb, u32
> pt_offset,
> +				       dma_addr_t *sram_addr, u32
> size)
> +{
> +	u16 pat_index = tile_to_xe(m->tile)->pat.idx[XE_CACHE_WB];
> +	u32 ptes;
> +	int i = 0;
> +
> +	ptes = DIV_ROUND_UP(size, XE_PAGE_SIZE);
> +	while (ptes) {
> +		u32 chunk = min(0x1ffU, ptes);
> +
> +		bb->cs[bb->len++] = MI_STORE_DATA_IMM |
> MI_SDI_NUM_QW(chunk);
> +		bb->cs[bb->len++] = pt_offset;
> +		bb->cs[bb->len++] = 0;
> +
> +		pt_offset += chunk * 8;
> +		ptes -= chunk;
> +
> +		while (chunk--) {
> +			u64 addr = sram_addr[i++] & PAGE_MASK;
> +
> +			xe_tile_assert(m->tile, addr);
> +			addr = m->q->vm->pt_ops->pte_encode_addr(m-
> >tile->xe,
> +								
> addr, pat_index,
> +								 0,
> false, 0);
> +			bb->cs[bb->len++] = lower_32_bits(addr);
> +			bb->cs[bb->len++] = upper_32_bits(addr);
> +		}
> +	}
> +}
> +
> +enum xe_migrate_copy_dir {
> +	XE_MIGRATE_COPY_TO_VRAM,
> +	XE_MIGRATE_COPY_TO_SRAM,
> +};
> +
> +static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
> +					 unsigned long npages,
> +					 dma_addr_t *sram_addr, u64
> vram_addr,
> +					 const enum
> xe_migrate_copy_dir dir)
> +{
> +	struct xe_gt *gt = m->tile->primary_gt;
> +	struct xe_device *xe = gt_to_xe(gt);
> +	struct dma_fence *fence = NULL;
> +	u32 batch_size = 2;
> +	u64 src_L0_ofs, dst_L0_ofs;
> +	u64 round_update_size;
> +	struct xe_sched_job *job;
> +	struct xe_bb *bb;
> +	u32 update_idx, pt_slot = 0;
> +	int err;
> +
> +	if (npages * PAGE_SIZE > MAX_PREEMPTDISABLE_TRANSFER)
> +		return ERR_PTR(-EINVAL);
> +
> +	round_update_size = npages * PAGE_SIZE;
> +	batch_size += pte_update_cmd_size(round_update_size);
> +	batch_size += EMIT_COPY_DW;
> +
> +	bb = xe_bb_new(gt, batch_size, true);
> +	if (IS_ERR(bb)) {
> +		err = PTR_ERR(bb);
> +		return ERR_PTR(err);
> +	}
> +
> +	build_pt_update_batch_sram(m, bb, pt_slot * XE_PAGE_SIZE,
> +				   sram_addr, round_update_size);
> +
> +	if (dir == XE_MIGRATE_COPY_TO_VRAM) {
> +		src_L0_ofs = xe_migrate_vm_addr(pt_slot, 0);
> +		dst_L0_ofs = xe_migrate_vram_ofs(xe, vram_addr,
> false);
> +
> +	} else {
> +		src_L0_ofs = xe_migrate_vram_ofs(xe, vram_addr,
> false);
> +		dst_L0_ofs = xe_migrate_vm_addr(pt_slot, 0);
> +	}
> +
> +	bb->cs[bb->len++] = MI_BATCH_BUFFER_END;
> +	update_idx = bb->len;
> +
> +	emit_copy(gt, bb, src_L0_ofs, dst_L0_ofs, round_update_size,
> +		  XE_PAGE_SIZE);
> +
> +	job = xe_bb_create_migration_job(m->q, bb,
> +					 xe_migrate_batch_base(m,
> true),
> +					 update_idx);
> +	if (IS_ERR(job)) {
> +		err = PTR_ERR(job);
> +		goto err;
> +	}
> +
> +	xe_sched_job_add_migrate_flush(job, 0);
> +
> +	mutex_lock(&m->job_mutex);
> +	xe_sched_job_arm(job);
> +	fence = dma_fence_get(&job->drm.s_fence->finished);
> +	xe_sched_job_push(job);
> +
> +	dma_fence_put(m->fence);
> +	m->fence = dma_fence_get(fence);
> +	mutex_unlock(&m->job_mutex);
> +
> +	xe_bb_free(bb, fence);
> +
> +	return fence;
> +
> +err:
> +	xe_bb_free(bb, NULL);
> +
> +	return ERR_PTR(err);
> +}
> +
> +/**
> + * xe_migrate_to_vram() - Migrate to VRAM
> + * @m: The migration context.
> + * @npages: Number of pages to migrate.
> + * @src_addr: Array of dma addresses (source of migrate)
> + * @dst_addr: Device physical address of VRAM (destination of
> migrate)
> + *
> + * Copy from an array dma addresses to a VRAM device physical
> address
> + *
> + * Return: dma fence for migrate to signal completion on succees,
> ERR_PTR on
> + * failure
> + */
> +struct dma_fence *xe_migrate_to_vram(struct xe_migrate *m,
> +				     unsigned long npages,
> +				     dma_addr_t *src_addr,
> +				     u64 dst_addr)
> +{
> +	return xe_migrate_vram(m, npages, src_addr, dst_addr,
> +			       XE_MIGRATE_COPY_TO_VRAM);
> +}
> +
> +/**
> + * xe_migrate_from_vram() - Migrate from VRAM
> + * @m: The migration context.
> + * @npages: Number of pages to migrate.
> + * @src_addr: Device physical address of VRAM (source of migrate)
> + * @dst_addr: Array of dma addresses (destination of migrate)
> + *
> + * Copy from a VRAM device physical address to an array dma
> addresses
> + *
> + * Return: dma fence for migrate to signal completion on succees,
> ERR_PTR on
> + * failure
> + */
> +struct dma_fence *xe_migrate_from_vram(struct xe_migrate *m,
> +				       unsigned long npages,
> +				       u64 src_addr,
> +				       dma_addr_t *dst_addr)
> +{
> +	return xe_migrate_vram(m, npages, dst_addr, src_addr,
> +			       XE_MIGRATE_COPY_TO_SRAM);
> +}
> +
>  #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
>  #include "tests/xe_migrate.c"
>  #endif
> diff --git a/drivers/gpu/drm/xe/xe_migrate.h
> b/drivers/gpu/drm/xe/xe_migrate.h
> index 0109866e398a..6ff9a963425c 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.h
> +++ b/drivers/gpu/drm/xe/xe_migrate.h
> @@ -95,6 +95,16 @@ struct xe_migrate_pt_update {
>  
>  struct xe_migrate *xe_migrate_init(struct xe_tile *tile);
>  
> +struct dma_fence *xe_migrate_to_vram(struct xe_migrate *m,
> +				     unsigned long npages,
> +				     dma_addr_t *src_addr,
> +				     u64 dst_addr);
> +
> +struct dma_fence *xe_migrate_from_vram(struct xe_migrate *m,
> +				       unsigned long npages,
> +				       u64 src_addr,
> +				       dma_addr_t *dst_addr);
> +
>  struct dma_fence *xe_migrate_copy(struct xe_migrate *m,
>  				  struct xe_bo *src_bo,
>  				  struct xe_bo *dst_bo,