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drm/xe: Split H2G and G2H into separate buffer objects

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H2G and G2H buffers have different access patterns (H2G is CPU-write,
GuC-read, while G2H is GPU-write, CPU-read). On dGPU, these patterns
benefit from different memory placements: H2G in VRAM and G2H in system
memory. Split the CT buffer into two separate buffers—one for H2G and
one for G2H—and select the optimal placement for each.

This provides a significant performance improvement on the G2H read
path, reducing a single read from ~20 µs to under 1 µs on BMG.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20260218043319.809548-2-matthew.brost@intel.com
This commit is contained in:
Matthew Brost
2026-02-17 20:33:17 -08:00
parent 2bcbf2dcde
commit af3de6cf06
2 changed files with 47 additions and 24 deletions
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67
drivers/gpu/drm/xe/xe_guc_ct.c
View File

@@ -255,6 +255,7 @@ static bool g2h_fence_needs_alloc(struct g2h_fence *g2h_fence)
#define CTB_DESC_SIZE ALIGN(sizeof(struct guc_ct_buffer_desc), SZ_2K)
#define CTB_H2G_BUFFER_OFFSET (CTB_DESC_SIZE * 2)
#define CTB_G2H_BUFFER_OFFSET (CTB_DESC_SIZE * 2)
#define CTB_H2G_BUFFER_SIZE (SZ_4K)
#define CTB_H2G_BUFFER_DWORDS (CTB_H2G_BUFFER_SIZE / sizeof(u32))
#define CTB_G2H_BUFFER_SIZE (SZ_128K)
@@ -279,10 +280,14 @@ long xe_guc_ct_queue_proc_time_jiffies(struct xe_guc_ct *ct)
return (CTB_H2G_BUFFER_SIZE / SZ_4K) * HZ;
}
static size_t guc_ct_size(void)
static size_t guc_h2g_size(void)
{
return CTB_H2G_BUFFER_OFFSET + CTB_H2G_BUFFER_SIZE +
CTB_G2H_BUFFER_SIZE;
return CTB_H2G_BUFFER_OFFSET + CTB_H2G_BUFFER_SIZE;
}
static size_t guc_g2h_size(void)
{
return CTB_G2H_BUFFER_OFFSET + CTB_G2H_BUFFER_SIZE;
}
static void guc_ct_fini(struct drm_device *drm, void *arg)
@@ -311,7 +316,8 @@ int xe_guc_ct_init_noalloc(struct xe_guc_ct *ct)
struct xe_gt *gt = ct_to_gt(ct);
int err;
xe_gt_assert(gt, !(guc_ct_size() % PAGE_SIZE));
xe_gt_assert(gt, !(guc_h2g_size() % PAGE_SIZE));
xe_gt_assert(gt, !(guc_g2h_size() % PAGE_SIZE));
err = drmm_mutex_init(&xe->drm, &ct->lock);
if (err)
@@ -356,7 +362,7 @@ int xe_guc_ct_init(struct xe_guc_ct *ct)
struct xe_tile *tile = gt_to_tile(gt);
struct xe_bo *bo;
bo = xe_managed_bo_create_pin_map(xe, tile, guc_ct_size(),
bo = xe_managed_bo_create_pin_map(xe, tile, guc_h2g_size(),
XE_BO_FLAG_SYSTEM |
XE_BO_FLAG_GGTT |
XE_BO_FLAG_GGTT_INVALIDATE |
@@ -364,7 +370,17 @@ int xe_guc_ct_init(struct xe_guc_ct *ct)
if (IS_ERR(bo))
return PTR_ERR(bo);
ct->bo = bo;
ct->ctbs.h2g.bo = bo;
bo = xe_managed_bo_create_pin_map(xe, tile, guc_g2h_size(),
XE_BO_FLAG_SYSTEM |
XE_BO_FLAG_GGTT |
XE_BO_FLAG_GGTT_INVALIDATE |
XE_BO_FLAG_PINNED_NORESTORE);
if (IS_ERR(bo))
return PTR_ERR(bo);
ct->ctbs.g2h.bo = bo;
return devm_add_action_or_reset(xe->drm.dev, guc_action_disable_ct, ct);
}
@@ -389,7 +405,7 @@ int xe_guc_ct_init_post_hwconfig(struct xe_guc_ct *ct)
xe_assert(xe, !xe_guc_ct_enabled(ct));
if (IS_DGFX(xe)) {
ret = xe_managed_bo_reinit_in_vram(xe, tile, &ct->bo);
ret = xe_managed_bo_reinit_in_vram(xe, tile, &ct->ctbs.h2g.bo);
if (ret)
return ret;
}
@@ -439,8 +455,7 @@ static void guc_ct_ctb_g2h_init(struct xe_device *xe, struct guc_ctb *g2h,
g2h->desc = IOSYS_MAP_INIT_OFFSET(map, CTB_DESC_SIZE);
xe_map_memset(xe, &g2h->desc, 0, 0, sizeof(struct guc_ct_buffer_desc));
g2h->cmds = IOSYS_MAP_INIT_OFFSET(map, CTB_H2G_BUFFER_OFFSET +
CTB_H2G_BUFFER_SIZE);
g2h->cmds = IOSYS_MAP_INIT_OFFSET(map, CTB_G2H_BUFFER_OFFSET);
}
static int guc_ct_ctb_h2g_register(struct xe_guc_ct *ct)
@@ -449,8 +464,8 @@ static int guc_ct_ctb_h2g_register(struct xe_guc_ct *ct)
u32 desc_addr, ctb_addr, size;
int err;
desc_addr = xe_bo_ggtt_addr(ct->bo);
ctb_addr = xe_bo_ggtt_addr(ct->bo) + CTB_H2G_BUFFER_OFFSET;
desc_addr = xe_bo_ggtt_addr(ct->ctbs.h2g.bo);
ctb_addr = xe_bo_ggtt_addr(ct->ctbs.h2g.bo) + CTB_H2G_BUFFER_OFFSET;
size = ct->ctbs.h2g.info.size * sizeof(u32);
err = xe_guc_self_cfg64(guc,
@@ -476,9 +491,8 @@ static int guc_ct_ctb_g2h_register(struct xe_guc_ct *ct)
u32 desc_addr, ctb_addr, size;
int err;
desc_addr = xe_bo_ggtt_addr(ct->bo) + CTB_DESC_SIZE;
ctb_addr = xe_bo_ggtt_addr(ct->bo) + CTB_H2G_BUFFER_OFFSET +
CTB_H2G_BUFFER_SIZE;
desc_addr = xe_bo_ggtt_addr(ct->ctbs.g2h.bo) + CTB_DESC_SIZE;
ctb_addr = xe_bo_ggtt_addr(ct->ctbs.g2h.bo) + CTB_G2H_BUFFER_OFFSET;
size = ct->ctbs.g2h.info.size * sizeof(u32);
err = xe_guc_self_cfg64(guc,
@@ -605,9 +619,12 @@ static int __xe_guc_ct_start(struct xe_guc_ct *ct, bool needs_register)
xe_gt_assert(gt, !xe_guc_ct_enabled(ct));
if (needs_register) {
xe_map_memset(xe, &ct->bo->vmap, 0, 0, xe_bo_size(ct->bo));
guc_ct_ctb_h2g_init(xe, &ct->ctbs.h2g, &ct->bo->vmap);
guc_ct_ctb_g2h_init(xe, &ct->ctbs.g2h, &ct->bo->vmap);
xe_map_memset(xe, &ct->ctbs.h2g.bo->vmap, 0, 0,
xe_bo_size(ct->ctbs.h2g.bo));
xe_map_memset(xe, &ct->ctbs.g2h.bo->vmap, 0, 0,
xe_bo_size(ct->ctbs.g2h.bo));
guc_ct_ctb_h2g_init(xe, &ct->ctbs.h2g, &ct->ctbs.h2g.bo->vmap);
guc_ct_ctb_g2h_init(xe, &ct->ctbs.g2h, &ct->ctbs.g2h.bo->vmap);
err = guc_ct_ctb_h2g_register(ct);
if (err)
@@ -624,7 +641,7 @@ static int __xe_guc_ct_start(struct xe_guc_ct *ct, bool needs_register)
ct->ctbs.h2g.info.broken = false;
ct->ctbs.g2h.info.broken = false;
/* Skip everything in H2G buffer */
xe_map_memset(xe, &ct->bo->vmap, CTB_H2G_BUFFER_OFFSET, 0,
xe_map_memset(xe, &ct->ctbs.h2g.bo->vmap, CTB_H2G_BUFFER_OFFSET, 0,
CTB_H2G_BUFFER_SIZE);
}
@@ -1962,8 +1979,9 @@ static struct xe_guc_ct_snapshot *guc_ct_snapshot_alloc(struct xe_guc_ct *ct, bo
if (!snapshot)
return NULL;
if (ct->bo && want_ctb) {
snapshot->ctb_size = xe_bo_size(ct->bo);
if (ct->ctbs.h2g.bo && ct->ctbs.g2h.bo && want_ctb) {
snapshot->ctb_size = xe_bo_size(ct->ctbs.h2g.bo) +
xe_bo_size(ct->ctbs.g2h.bo);
snapshot->ctb = kmalloc(snapshot->ctb_size, atomic ? GFP_ATOMIC : GFP_KERNEL);
}
@@ -2011,8 +2029,13 @@ static struct xe_guc_ct_snapshot *guc_ct_snapshot_capture(struct xe_guc_ct *ct,
guc_ctb_snapshot_capture(xe, &ct->ctbs.g2h, &snapshot->g2h);
}
if (ct->bo && snapshot->ctb)
xe_map_memcpy_from(xe, snapshot->ctb, &ct->bo->vmap, 0, snapshot->ctb_size);
if (ct->ctbs.h2g.bo && ct->ctbs.g2h.bo && snapshot->ctb) {
xe_map_memcpy_from(xe, snapshot->ctb, &ct->ctbs.h2g.bo->vmap, 0,
xe_bo_size(ct->ctbs.h2g.bo));
xe_map_memcpy_from(xe, snapshot->ctb + xe_bo_size(ct->ctbs.h2g.bo),
&ct->ctbs.g2h.bo->vmap, 0,
xe_bo_size(ct->ctbs.g2h.bo));
}
return snapshot;
}

4
drivers/gpu/drm/xe/xe_guc_ct_types.h
View File

@@ -39,6 +39,8 @@ struct guc_ctb_info {
* struct guc_ctb - GuC command transport buffer (CTB)
*/
struct guc_ctb {
/** @bo: Xe BO for CTB */
struct xe_bo *bo;
/** @desc: dma buffer map for CTB descriptor */
struct iosys_map desc;
/** @cmds: dma buffer map for CTB commands */
@@ -126,8 +128,6 @@ struct xe_fast_req_fence {
* for the H2G and G2H requests sent and received through the buffers.
*/
struct xe_guc_ct {
/** @bo: Xe BO for CT */
struct xe_bo *bo;
/** @lock: protects everything in CT layer */
struct mutex lock;
/** @fast_lock: protects G2H channel and credits */