Re: [Intel-gfx] [PATCH v3 7/8] drm/i915/migrate: add acceleration support for DG2

Ramalingam C
2021-12-16T15:03:23Z

On 2021-12-14 at 12:32:57 +0000, Matthew Auld wrote:
> On 14/12/2021 10:56, Ramalingam C wrote:
> > On 2021-12-06 at 13:31:39 +0000, Matthew Auld wrote:
> > > This is all kinds of awkward since we now have to contend with using 64K
> > > GTT pages when mapping anything in LMEM(including the page-tables
> > > themselves).
> > >
> > > Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> > > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > > Cc: Ramalingam C <ramalingam.c@intel.com>
> > > ---
> > > drivers/gpu/drm/i915/gt/intel_migrate.c | 189 +++++++++++++++++++-----
> > > 1 file changed, 150 insertions(+), 39 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c
> > > index 0192b61ab541..fb658ae70a8d 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_migrate.c
> > > +++ b/drivers/gpu/drm/i915/gt/intel_migrate.c
> > > @@ -33,6 +33,38 @@ static bool engine_supports_migration(struct intel_engine_cs *engine)
> > > return true;
> > > }
> > > +static void xehpsdv_toggle_pdes(struct i915_address_space *vm,
> > > + struct i915_page_table *pt,
> > > + void *data)
> > > +{
> > > + struct insert_pte_data *d = data;
> > > +
> > > + /*
> > > + * Insert a dummy PTE into every PT that will map to LMEM to ensure
> > > + * we have a correctly setup PDE structure for later use.
> > > + */
> > > + vm->insert_page(vm, 0, d->offset, I915_CACHE_NONE, PTE_LM);
> > This part i am not understanding. Why do we need to insert the dummy
> > PTE here.?
>
> We have three windows, each CHUNK_SIZE in size. The first is reserved for
> mapping system-memory, and that just uses the 512 entry layout using 4K GTT
> pages. The other two windows just map lmem pages and must use the new
> compact 32 entry layout using 64K GTT pages, which ensures we can address
> any lmem object that the user throws at us. The above is basically just
> toggling the PDE bit(GEN12_PDE_64K) for us, to enable the compact layout for
> each of these page-tables, that fall within the 2 * CHUNK_SIZE range
> starting at CHUNK_SIZE.

If we could summarize this into the comment it will be helpful.
Apart from this, change looks good to me.

Reviewed-by: Ramalingam C <ramalingam.c@intel.com>

>
>
> > > + GEM_BUG_ON(!pt->is_compact);
> > > + d->offset += SZ_2M;
> > > +}
> > > +
> > > +static void xehpsdv_insert_pte(struct i915_address_space *vm,
> > > + struct i915_page_table *pt,
> > > + void *data)
> > > +{
> > > + struct insert_pte_data *d = data;
> > > +
> > > + /*
> > > + * We are playing tricks here, since the actual pt, from the hw
> > > + * pov, is only 256bytes with 32 entries, or 4096bytes with 512
> > > + * entries, but we are still guaranteed that the physical
> > > + * alignment is 64K underneath for the pt, and we are careful
> > > + * not to access the space in the void.
> > > + */
> > > + vm->insert_page(vm, px_dma(pt), d->offset, I915_CACHE_NONE, PTE_LM);
> > > + d->offset += SZ_64K;
> > > +}
> > > +
> > > static void insert_pte(struct i915_address_space *vm,
> > > struct i915_page_table *pt,
> > > void *data)
> > > @@ -75,7 +107,12 @@ static struct i915_address_space *migrate_vm(struct intel_gt *gt)
> > > * i.e. within the same non-preemptible window so that we do not switch
> > > * to another migration context that overwrites the PTE.
> > > *
> > > - * TODO: Add support for huge LMEM PTEs
> > > + * On platforms with HAS_64K_PAGES support we have three windows, and
> > > + * dedicate two windows just for mapping lmem pages(smem <-> smem is not
> > > + * a thing), since we are forced to use 64K GTT pages underneath which
> > > + * requires also modifying the PDE. An alternative might be to instead
> > > + * map the PD into the GTT, and then on the fly toggle the 4K/64K mode
> > > + * in the PDE from the same batch that also modifies the PTEs.
> > Could we also add a layout of the ppGTT, incase of HAS_64K_PAGES?
>
> [0, CHUNK_SZ) -> first window, maps smem
> [CHUNK_SZ, 2 * CHUNK_SZ) -> second window, maps lmem src
> [2 * CHUNK_SZ, 3 * CHUNK_SZ) -> third window, maps lmem dst
>
> It starts to get strange here, since each PTE must point to some 64K page,
> one for each PT(since it's in lmem), and yet each is only <= 4096bytes, but
> since the unused space within that PTE range is never touched, this should
> be fine.
>
> So basically each PT now needs 64K of virtual memory, instead of 4K. So
> something like:
>
> [3 * CHUNK_SZ, 3 * CHUNK_SZ + ((3 * CHUNK_SZ / SZ_2M) * SZ_64K)] -> PTE
>
> And then later when writing out the PTEs we know if the layout within a
> particular PT is 512 vs 32 depending on if we are mapping lmem or not.
>
> > > */
> > > vm = i915_ppgtt_create(gt, I915_BO_ALLOC_PM_EARLY);
> > > @@ -87,6 +124,9 @@ static struct i915_address_space *migrate_vm(struct intel_gt *gt)
> > > goto err_vm;
> > > }
> > > + if (HAS_64K_PAGES(gt->i915))
> > > + stash.pt_sz = I915_GTT_PAGE_SIZE_64K;
> > > +
> > > /*
> > > * Each engine instance is assigned its own chunk in the VM, so
> > > * that we can run multiple instances concurrently
> > > @@ -106,14 +146,20 @@ static struct i915_address_space *migrate_vm(struct intel_gt *gt)
> > > * We copy in 8MiB chunks. Each PDE covers 2MiB, so we need
> > > * 4x2 page directories for source/destination.
> > > */
> > > - sz = 2 * CHUNK_SZ;
> > > + if (HAS_64K_PAGES(gt->i915))
> > > + sz = 3 * CHUNK_SZ;
> > > + else
> > > + sz = 2 * CHUNK_SZ;
> > > d.offset = base + sz;
> > > /*
> > > * We need another page directory setup so that we can write
> > > * the 8x512 PTE in each chunk.
> > > */
> > > - sz += (sz >> 12) * sizeof(u64);
> > > + if (HAS_64K_PAGES(gt->i915))
> > > + sz += (sz / SZ_2M) * SZ_64K;
> > > + else
> > > + sz += (sz >> 12) * sizeof(u64);
> > Here for 4K page support, per page we assume the u64 as the length required. But
> > for 64k page support we calculate the no of PDE and per PDE we allocate
> > the 64k page so that we can map it for edit right?
> >
> > In this case i assume we have the unused space at the end. say after
> > 32*sizeof(u64)
>
> For every PT(which is 2M va range), we need a 64K va chunk in order to map
> it. Yes, there is some unused space at the end, but it is already like that
> for the other PTEs. Also it seems strange to call alloc_va_range without
> also rounding up the size to the correct page size.
>
> >
> > Ram
> > > err = i915_vm_alloc_pt_stash(&vm->vm, &stash, sz);
> > > if (err)
> > > @@ -134,7 +180,18 @@ static struct i915_address_space *migrate_vm(struct intel_gt *gt)
> > > goto err_vm;
> > > /* Now allow the GPU to rewrite the PTE via its own ppGTT */
> > > - vm->vm.foreach(&vm->vm, base, d.offset - base, insert_pte, &d);
> > > + if (HAS_64K_PAGES(gt->i915)) {
> > > + vm->vm.foreach(&vm->vm, base, d.offset - base,
> > > + xehpsdv_insert_pte, &d);
> > > + d.offset = base + CHUNK_SZ;
> > > + vm->vm.foreach(&vm->vm,
> > > + d.offset,
> > > + 2 * CHUNK_SZ,
> > > + xehpsdv_toggle_pdes, &d);
> > > + } else {
> > > + vm->vm.foreach(&vm->vm, base, d.offset - base,
> > > + insert_pte, &d);
> > > + }
> > > }
> > > return &vm->vm;
> > > @@ -272,19 +329,38 @@ static int emit_pte(struct i915_request *rq,
> > > u64 offset,
> > > int length)
> > > {
> > > + bool has_64K_pages = HAS_64K_PAGES(rq->engine->i915);
> > > const u64 encode = rq->context->vm->pte_encode(0, cache_level,
> > > is_lmem ? PTE_LM : 0);
> > > struct intel_ring *ring = rq->ring;
> > > - int total = 0;
> > > + int pkt, dword_length;
> > > + u32 total = 0;
> > > + u32 page_size;
> > > u32 *hdr, *cs;
> > > - int pkt;
> > > GEM_BUG_ON(GRAPHICS_VER(rq->engine->i915) < 8);
> > > + page_size = I915_GTT_PAGE_SIZE;
> > > + dword_length = 0x400;
> > > +
> > > /* Compute the page directory offset for the target address range */
> > > - offset >>= 12;
> > > - offset *= sizeof(u64);
> > > - offset += 2 * CHUNK_SZ;
> > > + if (has_64K_pages) {
> > > + GEM_BUG_ON(!IS_ALIGNED(offset, SZ_2M));
> > > +
> > > + offset /= SZ_2M;
> > > + offset *= SZ_64K;
> > > + offset += 3 * CHUNK_SZ;
> > > +
> > > + if (is_lmem) {
> > > + page_size = I915_GTT_PAGE_SIZE_64K;
> > > + dword_length = 0x40;
> > > + }
> > > + } else {
> > > + offset >>= 12;
> > > + offset *= sizeof(u64);
> > > + offset += 2 * CHUNK_SZ;
> > > + }
> > > +
> > > offset += (u64)rq->engine->instance << 32;
> > > cs = intel_ring_begin(rq, 6);
> > > @@ -292,7 +368,7 @@ static int emit_pte(struct i915_request *rq,
> > > return PTR_ERR(cs);
> > > /* Pack as many PTE updates as possible into a single MI command */
> > > - pkt = min_t(int, 0x400, ring->space / sizeof(u32) + 5);
> > > + pkt = min_t(int, dword_length, ring->space / sizeof(u32) + 5);
> > > pkt = min_t(int, pkt, (ring->size - ring->emit) / sizeof(u32) + 5);
> > > hdr = cs;
> > > @@ -302,6 +378,8 @@ static int emit_pte(struct i915_request *rq,
> > > do {
> > > if (cs - hdr >= pkt) {
> > > + int dword_rem;
> > > +
> > > *hdr += cs - hdr - 2;
> > > *cs++ = MI_NOOP;
> > > @@ -313,7 +391,18 @@ static int emit_pte(struct i915_request *rq,
> > > if (IS_ERR(cs))
> > > return PTR_ERR(cs);
> > > - pkt = min_t(int, 0x400, ring->space / sizeof(u32) + 5);
> > > + dword_rem = dword_length;
> > > + if (has_64K_pages) {
> > > + if (IS_ALIGNED(total, SZ_2M)) {
> > > + offset = round_up(offset, SZ_64K);
> > > + } else {
> > > + dword_rem = SZ_2M - (total & (SZ_2M - 1));
> > > + dword_rem /= page_size;
> > > + dword_rem *= 2;
> > > + }
> > > + }
> > > +
> > > + pkt = min_t(int, dword_rem, ring->space / sizeof(u32) + 5);
> > > pkt = min_t(int, pkt, (ring->size - ring->emit) / sizeof(u32) + 5);
> > > hdr = cs;
> > > @@ -322,13 +411,15 @@ static int emit_pte(struct i915_request *rq,
> > > *cs++ = upper_32_bits(offset);
> > > }
> > > + GEM_BUG_ON(!IS_ALIGNED(it->dma, page_size));
> > > +
> > > *cs++ = lower_32_bits(encode | it->dma);
> > > *cs++ = upper_32_bits(encode | it->dma);
> > > offset += 8;
> > > - total += I915_GTT_PAGE_SIZE;
> > > + total += page_size;
> > > - it->dma += I915_GTT_PAGE_SIZE;
> > > + it->dma += page_size;
> > > if (it->dma >= it->max) {
> > > it->sg = __sg_next(it->sg);
> > > if (!it->sg || sg_dma_len(it->sg) == 0)
> > > @@ -359,7 +450,8 @@ static bool wa_1209644611_applies(int ver, u32 size)
> > > return height % 4 == 3 && height <= 8;
> > > }
> > > -static int emit_copy(struct i915_request *rq, int size)
> > > +static int emit_copy(struct i915_request *rq,
> > > + u32 dst_offset, u32 src_offset, int size)
> > > {
> > > const int ver = GRAPHICS_VER(rq->engine->i915);
> > > u32 instance = rq->engine->instance;
> > > @@ -374,31 +466,31 @@ static int emit_copy(struct i915_request *rq, int size)
> > > *cs++ = BLT_DEPTH_32 | PAGE_SIZE;
> > > *cs++ = 0;
> > > *cs++ = size >> PAGE_SHIFT << 16 | PAGE_SIZE / 4;
> > > - *cs++ = CHUNK_SZ; /* dst offset */
> > > + *cs++ = dst_offset;
> > > *cs++ = instance;
> > > *cs++ = 0;
> > > *cs++ = PAGE_SIZE;
> > > - *cs++ = 0; /* src offset */
> > > + *cs++ = src_offset;
> > > *cs++ = instance;
> > > } else if (ver >= 8) {
> > > *cs++ = XY_SRC_COPY_BLT_CMD | BLT_WRITE_RGBA | (10 - 2);
> > > *cs++ = BLT_DEPTH_32 | BLT_ROP_SRC_COPY | PAGE_SIZE;
> > > *cs++ = 0;
> > > *cs++ = size >> PAGE_SHIFT << 16 | PAGE_SIZE / 4;
> > > - *cs++ = CHUNK_SZ; /* dst offset */
> > > + *cs++ = dst_offset;
> > > *cs++ = instance;
> > > *cs++ = 0;
> > > *cs++ = PAGE_SIZE;
> > > - *cs++ = 0; /* src offset */
> > > + *cs++ = src_offset;
> > > *cs++ = instance;
> > > } else {
> > > GEM_BUG_ON(instance);
> > > *cs++ = SRC_COPY_BLT_CMD | BLT_WRITE_RGBA | (6 - 2);
> > > *cs++ = BLT_DEPTH_32 | BLT_ROP_SRC_COPY | PAGE_SIZE;
> > > *cs++ = size >> PAGE_SHIFT << 16 | PAGE_SIZE;
> > > - *cs++ = CHUNK_SZ; /* dst offset */
> > > + *cs++ = dst_offset;
> > > *cs++ = PAGE_SIZE;
> > > - *cs++ = 0; /* src offset */
> > > + *cs++ = src_offset;
> > > }
> > > intel_ring_advance(rq, cs);
> > > @@ -426,6 +518,7 @@ intel_context_migrate_copy(struct intel_context *ce,
> > > GEM_BUG_ON(ce->ring->size < SZ_64K);
> > > do {
> > > + u32 src_offset, dst_offset;
> > > int len;
> > > rq = i915_request_create(ce);
> > > @@ -453,15 +546,28 @@ intel_context_migrate_copy(struct intel_context *ce,
> > > if (err)
> > > goto out_rq;
> > > - len = emit_pte(rq, &it_src, src_cache_level, src_is_lmem, 0,
> > > - CHUNK_SZ);
> > > + src_offset = 0;
> > > + dst_offset = CHUNK_SZ;
> > > + if (HAS_64K_PAGES(ce->engine->i915)) {
> > > + GEM_BUG_ON(!src_is_lmem && !dst_is_lmem);
> > > +
> > > + src_offset = 0;
> > > + dst_offset = 0;
> > > + if (src_is_lmem)
> > > + src_offset = CHUNK_SZ;
> > > + if (dst_is_lmem)
> > > + dst_offset = 2 * CHUNK_SZ;
> > > + }
> > > +
> > > + len = emit_pte(rq, &it_src, src_cache_level, src_is_lmem,
> > > + src_offset, CHUNK_SZ);
> > > if (len <= 0) {
> > > err = len;
> > > goto out_rq;
> > > }
> > > err = emit_pte(rq, &it_dst, dst_cache_level, dst_is_lmem,
> > > - CHUNK_SZ, len);
> > > + dst_offset, len);
> > > if (err < 0)
> > > goto out_rq;
> > > if (err < len) {
> > > @@ -473,7 +579,7 @@ intel_context_migrate_copy(struct intel_context *ce,
> > > if (err)
> > > goto out_rq;
> > > - err = emit_copy(rq, len);
> > > + err = emit_copy(rq, dst_offset, src_offset, len);
> > > /* Arbitration is re-enabled between requests. */
> > > out_rq:
> > > @@ -571,18 +677,20 @@ static u32 *_i915_ctrl_surf_copy_blt(u32 *cmd, u64 src_addr, u64 dst_addr,
> > > }
> > > static int emit_clear(struct i915_request *rq,
> > > + u64 offset,
> > > int size,
> > > u32 value,
> > > bool is_lmem)
> > > {
> > > - const int ver = GRAPHICS_VER(rq->engine->i915);
> > > - u32 instance = rq->engine->instance;
> > > - u32 *cs;
> > > struct drm_i915_private *i915 = rq->engine->i915;
> > > + const int ver = GRAPHICS_VER(rq->engine->i915);
> > > u32 num_ccs_blks, ccs_ring_size;
> > > + u32 *cs;
> > > GEM_BUG_ON(size >> PAGE_SHIFT > S16_MAX);
> > > + offset += (u64)rq->engine->instance << 32;
> > > +
> > > /* Clear flat css only when value is 0 */
> > > ccs_ring_size = (is_lmem && !value) ?
> > > calc_ctrl_surf_instr_size(i915, size)
> > > @@ -597,17 +705,17 @@ static int emit_clear(struct i915_request *rq,
> > > *cs++ = BLT_DEPTH_32 | BLT_ROP_COLOR_COPY | PAGE_SIZE;
> > > *cs++ = 0;
> > > *cs++ = size >> PAGE_SHIFT << 16 | PAGE_SIZE / 4;
> > > - *cs++ = 0; /* offset */
> > > - *cs++ = instance;
> > > + *cs++ = lower_32_bits(offset);
> > > + *cs++ = upper_32_bits(offset);
> > > *cs++ = value;
> > > *cs++ = MI_NOOP;
> > > } else {
> > > - GEM_BUG_ON(instance);
> > > + GEM_BUG_ON(upper_32_bits(offset));
> > > *cs++ = XY_COLOR_BLT_CMD | BLT_WRITE_RGBA | (6 - 2);
> > > *cs++ = BLT_DEPTH_32 | BLT_ROP_COLOR_COPY | PAGE_SIZE;
> > > *cs++ = 0;
> > > *cs++ = size >> PAGE_SHIFT << 16 | PAGE_SIZE / 4;
> > > - *cs++ = 0;
> > > + *cs++ = lower_32_bits(offset);
> > > *cs++ = value;
> > > }
> > > @@ -623,17 +731,15 @@ static int emit_clear(struct i915_request *rq,
> > > * and use it as a source.
> > > */
> > > - cs = i915_flush_dw(cs, (u64)instance << 32,
> > > - MI_FLUSH_LLC | MI_FLUSH_CCS);
> > > + cs = i915_flush_dw(cs, offset, MI_FLUSH_LLC | MI_FLUSH_CCS);
> > > cs = _i915_ctrl_surf_copy_blt(cs,
> > > - (u64)instance << 32,
> > > - (u64)instance << 32,
> > > + offset,
> > > + offset,
> > > DIRECT_ACCESS,
> > > INDIRECT_ACCESS,
> > > 1, 1,
> > > num_ccs_blks);
> > > - cs = i915_flush_dw(cs, (u64)instance << 32,
> > > - MI_FLUSH_LLC | MI_FLUSH_CCS);
> > > + cs = i915_flush_dw(cs, offset, MI_FLUSH_LLC | MI_FLUSH_CCS);
> > > }
> > > intel_ring_advance(rq, cs);
> > > return 0;
> > > @@ -658,6 +764,7 @@ intel_context_migrate_clear(struct intel_context *ce,
> > > GEM_BUG_ON(ce->ring->size < SZ_64K);
> > > do {
> > > + u32 offset;
> > > int len;
> > > rq = i915_request_create(ce);
> > > @@ -685,7 +792,11 @@ intel_context_migrate_clear(struct intel_context *ce,
> > > if (err)
> > > goto out_rq;
> > > - len = emit_pte(rq, &it, cache_level, is_lmem, 0, CHUNK_SZ);
> > > + offset = 0;
> > > + if (HAS_64K_PAGES(ce->engine->i915) && is_lmem)
> > > + offset = CHUNK_SZ;
> > > +
> > > + len = emit_pte(rq, &it, cache_level, is_lmem, offset, CHUNK_SZ);
> > > if (len <= 0) {
> > > err = len;
> > > goto out_rq;
> > > @@ -695,7 +806,7 @@ intel_context_migrate_clear(struct intel_context *ce,
> > > if (err)
> > > goto out_rq;
> > > - err = emit_clear(rq, len, value, is_lmem);
> > > + err = emit_clear(rq, offset, len, value, is_lmem);
> > > /* Arbitration is re-enabled between requests. */
> > > out_rq:
> > > --
> > > 2.31.1
> > >