Re: [PATCH v2 16/29] drm/xe: Add migrate layer functions for SVM support

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

On Tue, Nov 19, 2024 at 05:45:27PM +0100, Thomas Hellström wrote:
> On Tue, 2024-10-15 at 20:25 -0700, Matthew Brost wrote:
> > Add functions which migrate to / from VRAM accepting a single DPA
> > argument (VRAM) and array of dma addresses (SRAM).
> > 
> > v2:
> >  - Don't unlock job_mutex in error path of xe_migrate_vram
> > 
> > Signed-off-by: Oak Zeng <oak.zeng@intel.com>
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_migrate.c | 149
> > ++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/xe/xe_migrate.h |  10 +++
> >  2 files changed, 159 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_migrate.c
> > b/drivers/gpu/drm/xe/xe_migrate.c
> > index cfd31ae49cc1..d7b6636286ae 100644
> > --- a/drivers/gpu/drm/xe/xe_migrate.c
> > +++ b/drivers/gpu/drm/xe/xe_migrate.c
> > @@ -1542,6 +1542,155 @@ void xe_migrate_wait(struct xe_migrate *m)
> >  		dma_fence_wait(m->fence, false);
> >  }
> >  
> > +static u32 pte_update_cmd_size(u64 size)
> > +{
> > +	u32 dword;
> 
> dwords or num_dword?
> 

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)
> > +	 */
> > +	dword = (1 + 2) * DIV_ROUND_UP(entries, 0x1ff);
> > +	dword += entries * 2;
> > +
> > +	return 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;
> > +
> > +	round_update_size = min_t(u64, npages * PAGE_SIZE,
> > +				  MAX_PREEMPTDISABLE_TRANSFER);
> 
> Hm. How does the caller know how many pages were actually migrated?
> 

This is an intermediate between migrate_vma_setup and
migrate_vma_pages/finalize. The number of pages here is based on mpfn
returned from migrate_vma_setup. The migration for individual pages may
still be aborted in migrate_vma_pages/finalize. In this case both the
old and new page have the same data, dso migrate_vma_pages/finalize can
pick either page.

> > +	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);
> > +}
> > +
> > +struct dma_fence *xe_migrate_to_vram(struct xe_migrate *m,
> > +				     unsigned long npages,
> > +				     dma_addr_t *src_addr,
> > +				     u64 dst_addr)
> 
> Kerneldoc.
>

Yep.
 
> > +{
> > +	return xe_migrate_vram(m, npages, src_addr, dst_addr,
> > +			       XE_MIGRATE_COPY_TO_VRAM);
> > +}
> > +
> > +struct dma_fence *xe_migrate_from_vram(struct xe_migrate *m,
> > +				       unsigned long npages,
> > +				       u64 src_addr,
> > +				       dma_addr_t *dst_addr)
> 
> Kerneldoc.
> 

Yep.

Matt

> > +{
> > +	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,
>