[PATCH v3 1/1] drm/i915/ehl: Add sysfs interface to control class-of-service

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To provide shared last-level-cache isolation to cpu workloads running
concurrently with gpu workloads, the gpu allocation of cache lines needs
to be restricted to certain ways. Currently GPU hardware supports four
class-of-service(CLOS) levels and there is an associated way-mask for
each CLOS. Each LLC MOCS register has a field to select the clos level.
So in-order to globally set the gpu to a clos level, driver needs
to program entire MOCS table.

Hardware supports reading supported way-mask configuration for GPU using
a bios pcode interface. This interface has two files--llc_clos_modes and
llc_clos. The file llc_clos_modes is read only file and will list the
available way masks. The file llc_clos is read/write and will show the
currently active way mask and writing a new way mask will update the
active way mask of the gpu.

Note of Caution: Restricting cache ways using this mechanism presents a
larger attack surface for side-channel attacks.

Example usage:
> cat /sys/class/drm/card0/llc_clos_modes
0xfff 0xfc0 0xc00 0x800

>cat /sys/class/drm/card0/llc_clos
0xfff

Update to new clos
echo "0x800" > /sys/class/drm/card0/llc_clos

Signed-off-by: Prathap Kumar Valsan <prathap.kumar.valsan@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c     |   7 +
 drivers/gpu/drm/i915/gt/intel_lrc_reg.h |   1 +
 drivers/gpu/drm/i915/gt/intel_mocs.c    | 216 +++++++++++++++++++++++-
 drivers/gpu/drm/i915/gt/intel_mocs.h    |   6 +-
 drivers/gpu/drm/i915/i915_drv.h         |   8 +
 drivers/gpu/drm/i915/i915_reg.h         |   1 +
 drivers/gpu/drm/i915/i915_sysfs.c       | 100 +++++++++++
 7 files changed, 337 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 468438fb47af..054051969d00 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2137,6 +2137,13 @@ __execlists_update_reg_state(const struct intel_context *ce,
 			intel_sseu_make_rpcs(engine->i915, &ce->sseu);
 
 		i915_oa_init_reg_state(ce, engine);
+		/*
+		 * Gen11+ wants to support update of LLC class-of-service via
+		 * sysfs interface. CLOS is defined in MOCS registers and for
+		 * Gen11, MOCS is part of context resgister state.
+		 */
+		if (IS_GEN(engine->i915, 11))
+			intel_mocs_init_reg_state(ce);
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc_reg.h b/drivers/gpu/drm/i915/gt/intel_lrc_reg.h
index 06ab0276e10e..f07a6262217c 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc_reg.h
+++ b/drivers/gpu/drm/i915/gt/intel_lrc_reg.h
@@ -28,6 +28,7 @@
 #define CTX_R_PWR_CLK_STATE		(0x42 + 1)
 
 #define GEN9_CTX_RING_MI_MODE		0x54
+#define GEN11_CTX_GFX_MOCS_BASE		0x4F2
 
 /* GEN12+ Reg State Context */
 #define GEN12_CTX_BB_PER_CTX_PTR		(0x12 + 1)
diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
index 728704bbbe18..a2669bee9b1b 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -26,6 +26,9 @@
 #include "intel_gt.h"
 #include "intel_mocs.h"
 #include "intel_lrc.h"
+#include "intel_lrc_reg.h"
+#include "intel_sideband.h"
+#include "gem/i915_gem_context.h"
 
 /* structures required */
 struct drm_i915_mocs_entry {
@@ -40,6 +43,7 @@ struct drm_i915_mocs_table {
 	const struct drm_i915_mocs_entry *table;
 };
 
+#define ctx_mocsN(N) (GEN11_CTX_GFX_MOCS_BASE + 2 * (N) + 1)
 /* Defines for the tables (XXX_MOCS_0 - XXX_MOCS_63) */
 #define _LE_CACHEABILITY(value)	((value) << 0)
 #define _LE_TGT_CACHE(value)	((value) << 2)
@@ -51,6 +55,7 @@ struct drm_i915_mocs_table {
 #define LE_SCF(value)		((value) << 14)
 #define LE_COS(value)		((value) << 15)
 #define LE_SSE(value)		((value) << 17)
+#define LE_COS_MASK		GENMASK(16, 15)
 
 /* Defines for the tables (LNCFMOCS0 - LNCFMOCS31) - two entries per word */
 #define L3_ESC(value)		((value) << 0)
@@ -377,6 +382,7 @@ void intel_mocs_init_engine(struct intel_engine_cs *engine)
 	struct intel_gt *gt = engine->gt;
 	struct intel_uncore *uncore = gt->uncore;
 	struct drm_i915_mocs_table table;
+	unsigned int active_clos;
 	unsigned int index;
 	u32 unused_value;
 
@@ -390,11 +396,16 @@ void intel_mocs_init_engine(struct intel_engine_cs *engine)
 	if (!get_mocs_settings(gt, &table))
 		return;
 
+	active_clos = engine->i915->clos.active_clos;
 	/* Set unused values to PTE */
 	unused_value = table.table[I915_MOCS_PTE].control_value;
+	unused_value &= ~LE_COS_MASK;
+	unused_value |= FIELD_PREP(LE_COS_MASK, active_clos);
 
 	for (index = 0; index < table.size; index++) {
 		u32 value = get_entry_control(&table, index);
+		value &= ~LE_COS_MASK;
+		value |= FIELD_PREP(LE_COS_MASK, active_clos);
 
 		intel_uncore_write_fw(uncore,
 				      mocs_register(engine->id, index),
@@ -408,7 +419,7 @@ void intel_mocs_init_engine(struct intel_engine_cs *engine)
 				      unused_value);
 }
 
-static void intel_mocs_init_global(struct intel_gt *gt)
+void intel_mocs_init_global(struct intel_gt *gt)
 {
 	struct intel_uncore *uncore = gt->uncore;
 	struct drm_i915_mocs_table table;
@@ -442,6 +453,7 @@ static int emit_mocs_control_table(struct i915_request *rq,
 				   const struct drm_i915_mocs_table *table)
 {
 	enum intel_engine_id engine = rq->engine->id;
+	unsigned int active_clos;
 	unsigned int index;
 	u32 unused_value;
 	u32 *cs;
@@ -449,8 +461,11 @@ static int emit_mocs_control_table(struct i915_request *rq,
 	if (GEM_WARN_ON(table->size > table->n_entries))
 		return -ENODEV;
 
+	active_clos = rq->i915->clos.active_clos;
 	/* Set unused values to PTE */
 	unused_value = table->table[I915_MOCS_PTE].control_value;
+	unused_value &= ~LE_COS_MASK;
+	unused_value |= FIELD_PREP(LE_COS_MASK, active_clos);
 
 	cs = intel_ring_begin(rq, 2 + 2 * table->n_entries);
 	if (IS_ERR(cs))
@@ -460,6 +475,8 @@ static int emit_mocs_control_table(struct i915_request *rq,
 
 	for (index = 0; index < table->size; index++) {
 		u32 value = get_entry_control(table, index);
+		value &= ~LE_COS_MASK;
+		value |= FIELD_PREP(LE_COS_MASK, active_clos);
 
 		*cs++ = i915_mmio_reg_offset(mocs_register(engine, index));
 		*cs++ = value;
@@ -625,10 +642,207 @@ int intel_mocs_emit(struct i915_request *rq)
 	return 0;
 }
 
+void intel_mocs_init_reg_state(const struct intel_context *ce)
+{
+	struct drm_i915_private *i915 = ce->engine->i915;
+	u32 *reg_state = ce->lrc_reg_state;
+	struct drm_i915_mocs_table t;
+	unsigned int active_clos;
+	u32 value;
+	int i;
+
+	get_mocs_settings(ce->engine->gt, &t);
+
+	active_clos = i915->clos.active_clos;
+
+	if (active_clos == FIELD_GET(LE_COS_MASK, get_entry_control(&t, 0)))
+		return;
+
+	for (i = 0; i < t.n_entries; i++) {
+		value = reg_state[ctx_mocsN(i)];
+		value &= ~LE_COS_MASK;
+		value |= FIELD_PREP(LE_COS_MASK, active_clos);
+		reg_state[ctx_mocsN(i)] = value;
+	}
+}
+
+static int
+mocs_store_clos(struct i915_request *rq,
+		struct intel_context *ce)
+{
+	struct drm_i915_mocs_table t;
+	unsigned int count, active_clos, index;
+	u32 offset;
+	u32 value;
+	u32 *cs;
+
+	if (!get_mocs_settings(rq->engine->gt, &t))
+		return -ENODEV;
+
+	count = t.n_entries;
+	active_clos = rq->i915->clos.active_clos;
+	cs = intel_ring_begin(rq, 4 * count);
+	if (IS_ERR(cs))
+		return PTR_ERR(cs);
+
+	offset = i915_ggtt_offset(ce->state) + LRC_STATE_PN * PAGE_SIZE;
+
+	for (index = 0; index < count; index++) {
+		value = ce->lrc_reg_state[ctx_mocsN(index)];
+		value &= ~LE_COS_MASK;
+		value |= FIELD_PREP(LE_COS_MASK, active_clos);
+
+		*cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
+		*cs++ = offset + ctx_mocsN(index) * sizeof(uint32_t);
+		*cs++ = 0;
+		*cs++ = value;
+	}
+
+	intel_ring_advance(rq, cs);
+
+	return 0;
+}
+
+static int modify_context_mocs(struct intel_context *ce)
+{
+	struct i915_request *rq;
+	int err;
+
+	lockdep_assert_held(&ce->pin_mutex);
+
+	rq = i915_request_create(ce->engine->kernel_context);
+	if (IS_ERR(rq))
+		return PTR_ERR(rq);
+
+	/* Serialise with the remote context */
+	err = intel_context_prepare_remote_request(ce, rq);
+	if (err == 0)
+		err = mocs_store_clos(rq, ce);
+
+	i915_request_add(rq);
+	return err;
+}
+
+static int intel_mocs_configure_context(struct i915_gem_context *ctx)
+{
+	struct i915_gem_engines_iter it;
+	struct intel_context *ce;
+	int err = 0;
+
+	for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it) {
+		GEM_BUG_ON(ce == ce->engine->kernel_context);
+
+		if (ce->engine->class != RENDER_CLASS)
+			continue;
+
+		err = intel_context_lock_pinned(ce);
+		if (err)
+			break;
+
+		if (intel_context_is_pinned(ce))
+			err = modify_context_mocs(ce);
+
+		intel_context_unlock_pinned(ce);
+		if (err)
+			break;
+	}
+	i915_gem_context_unlock_engines(ctx);
+
+	return err;
+}
+
+static int intel_mocs_configure_all_contexts(struct intel_gt *gt)
+{
+	struct drm_i915_private *i915 = gt->i915;
+	struct intel_engine_cs *engine;
+	struct i915_gem_context *ctx;
+	enum intel_engine_id id;
+	int err;
+
+	lockdep_assert_held(&i915->drm.struct_mutex);
+	/*
+	 * MOCS registers of render engine are context saved and restored to and
+	 * from a context image.
+	 * So for any MOCS update to reflect on the existing contexts requires
+	 * updating the context image.
+	 */
+	list_for_each_entry(ctx, &i915->gem.contexts.list, link) {
+		if (ctx == i915->kernel_context)
+			continue;
+
+		err = intel_mocs_configure_context(ctx);
+		if (err)
+			return err;
+	}
+
+	/*
+	 * After updating all other contexts, update render context image of
+	 * kernel context. Also update the MOCS of non-render engines.
+	 */
+
+	for_each_engine(engine, i915, id) {
+		struct i915_request *rq;
+		struct drm_i915_mocs_table t;
+
+		rq = i915_request_create(engine->kernel_context);
+		if (IS_ERR(rq))
+			return PTR_ERR(rq);
+
+		get_mocs_settings(rq->engine->gt, &t);
+		err = emit_mocs_control_table(rq, &t);
+		if (err) {
+			i915_request_skip(rq, err);
+			i915_request_add(rq);
+			return err;
+		}
+
+		i915_request_add(rq);
+	}
+
+	return 0;
+}
+
+int intel_mocs_update_clos(struct intel_gt *gt)
+{
+	return intel_mocs_configure_all_contexts(gt);
+}
+
+static void intel_read_clos_way_mask(struct intel_gt *gt)
+{
+	struct drm_i915_private *i915 = gt->i915;
+	struct drm_i915_mocs_table table;
+	int ret, i;
+	u32 val;
+
+	if (!get_mocs_settings(gt, &table))
+		return;
+
+	/* CLOS is same for all entries. So its enough to read one*/
+	i915->clos.active_clos = FIELD_GET(LE_COS_MASK,
+					   get_entry_control(&table, 0));
+	for (i = 0; i < NUM_OF_CLOS; i++) {
+		val = i;
+		ret = sandybridge_pcode_read(i915,
+					     ICL_PCODE_LLC_COS_WAY_MASK_INFO,
+					     &val, NULL);
+		if (ret) {
+			DRM_ERROR("Mailbox read error = %d\n", ret);
+			return;
+		}
+
+		i915->clos.way_mask[i] = val;
+	}
+
+	i915->clos.support_way_mask_read = true;
+}
+
 void intel_mocs_init(struct intel_gt *gt)
 {
 	intel_mocs_init_l3cc_table(gt);
 
+	if (IS_GEN(gt->i915, 11))
+		intel_read_clos_way_mask(gt);
+
 	if (HAS_GLOBAL_MOCS_REGISTERS(gt->i915))
 		intel_mocs_init_global(gt);
 }
diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.h b/drivers/gpu/drm/i915/gt/intel_mocs.h
index 2ae816b7ca19..65566457408e 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.h
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.h
@@ -49,13 +49,17 @@
  * context handling keep the MOCS in step.
  */
 
-struct i915_request;
 struct intel_engine_cs;
+struct intel_context;
+struct i915_request;
 struct intel_gt;
 
 void intel_mocs_init(struct intel_gt *gt);
 void intel_mocs_init_engine(struct intel_engine_cs *engine);
 
 int intel_mocs_emit(struct i915_request *rq);
+int intel_mocs_update_clos(struct intel_gt *gt);
+
+void intel_mocs_init_reg_state(const struct intel_context *ce);
 
 #endif
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index cde4c7fb5570..01c5f7fec634 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1604,6 +1604,14 @@ struct drm_i915_private {
 		bool distrust_bios_wm;
 	} wm;
 
+	/* Last Level Cache  Class of Service */
+	struct {
+		bool support_way_mask_read;
+		u8 active_clos;
+#define NUM_OF_CLOS 4
+		u16 way_mask[NUM_OF_CLOS];
+	} clos;
+
 	struct dram_info {
 		bool valid;
 		bool is_16gb_dimm;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 6d67bd238cfe..0a7937234975 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -8859,6 +8859,7 @@ enum {
 #define   ICL_PCODE_MEM_SUBSYSYSTEM_INFO	0xd
 #define     ICL_PCODE_MEM_SS_READ_GLOBAL_INFO	(0x0 << 8)
 #define     ICL_PCODE_MEM_SS_READ_QGV_POINT_INFO(point)	(((point) << 16) | (0x1 << 8))
+#define   ICL_PCODE_LLC_COS_WAY_MASK_INFO	0x1d
 #define   GEN6_PCODE_READ_D_COMP		0x10
 #define   GEN6_PCODE_WRITE_D_COMP		0x11
 #define   HSW_PCODE_DE_WRITE_FREQ_REQ		0x17
diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
index bf039b8ba593..8344ad2380cc 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -36,6 +36,7 @@
 #include "i915_sysfs.h"
 #include "intel_pm.h"
 #include "intel_sideband.h"
+#include "gt/intel_mocs.h"
 
 static inline struct drm_i915_private *kdev_minor_to_i915(struct device *kdev)
 {
@@ -255,6 +256,88 @@ static const struct bin_attribute dpf_attrs_1 = {
 	.private = (void *)1
 };
 
+static ssize_t llc_clos_show(struct device *kdev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct drm_i915_private *dev_priv = kdev_minor_to_i915(kdev);
+	ssize_t len = 0;
+	int active_clos;
+
+	active_clos = dev_priv->clos.active_clos;
+	len += snprintf(buf + len, PAGE_SIZE, "0x%x\n",
+			dev_priv->clos.way_mask[active_clos]);
+
+	return len;
+}
+
+static ssize_t llc_clos_store(struct device *kdev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct drm_i915_private *dev_priv = kdev_minor_to_i915(kdev);
+	struct drm_device *dev = &dev_priv->drm;
+	u8 active_clos, new_clos, clos_index;
+	bool valid_mask = false;
+	ssize_t ret;
+	u16 way_mask;
+
+	ret = kstrtou16(buf, 0, &way_mask);
+	if (ret)
+		return ret;
+
+	active_clos = dev_priv->clos.active_clos;
+
+	if (dev_priv->clos.way_mask[active_clos] == way_mask)
+		return count;
+
+	for (clos_index = 0; clos_index < NUM_OF_CLOS; clos_index++) {
+		if (dev_priv->clos.way_mask[clos_index] == way_mask) {
+			new_clos = clos_index;
+			valid_mask = true;
+			break;
+		}
+	}
+
+	if (!valid_mask)
+		return -EINVAL;
+
+	ret = i915_mutex_lock_interruptible(dev);
+	if (ret)
+		return ret;
+
+	dev_priv->clos.active_clos = new_clos;
+	ret = intel_mocs_update_clos(&dev_priv->gt);
+	if (ret) {
+		DRM_ERROR("Failed to update Class of service\n");
+		dev_priv->clos.active_clos = active_clos;
+		mutex_unlock(&dev->struct_mutex);
+		return ret;
+	}
+
+	mutex_unlock(&dev->struct_mutex);
+
+	return count;
+}
+
+static ssize_t llc_clos_modes_show(struct device *kdev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct drm_i915_private *dev_priv = kdev_minor_to_i915(kdev);
+	ssize_t len = 0;
+	int i;
+
+	for (i = 0; i < NUM_OF_CLOS; i++)
+		len += snprintf(buf + len, PAGE_SIZE, "0x%x ",
+				dev_priv->clos.way_mask[i]);
+
+	len += snprintf(buf + len, PAGE_SIZE, "\n");
+
+	return len;
+}
+
+static DEVICE_ATTR_RW(llc_clos);
+static DEVICE_ATTR_RO(llc_clos_modes);
+
 static ssize_t gt_act_freq_mhz_show(struct device *kdev,
 				    struct device_attribute *attr, char *buf)
 {
@@ -574,6 +657,18 @@ void i915_setup_sysfs(struct drm_i915_private *dev_priv)
 	struct device *kdev = dev_priv->drm.primary->kdev;
 	int ret;
 
+	if (dev_priv->clos.support_way_mask_read) {
+		ret = sysfs_create_file(&kdev->kobj,
+					&dev_attr_llc_clos.attr);
+		if (ret)
+			DRM_ERROR("LLC COS sysfs setup failed\n");
+
+		ret = sysfs_create_file(&kdev->kobj,
+					&dev_attr_llc_clos_modes.attr);
+		if (ret)
+			DRM_ERROR("LLC COS sysfs setup failed\n");
+	}
+
 #ifdef CONFIG_PM
 	if (HAS_RC6(dev_priv)) {
 		ret = sysfs_merge_group(&kdev->kobj,
@@ -624,6 +719,11 @@ void i915_teardown_sysfs(struct drm_i915_private *dev_priv)
 
 	i915_teardown_error_capture(kdev);
 
+	if (dev_priv->clos.support_way_mask_read) {
+		sysfs_remove_file(&kdev->kobj, &dev_attr_llc_clos.attr);
+		sysfs_remove_file(&kdev->kobj, &dev_attr_llc_clos_modes.attr);
+	}
+
 	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
 		sysfs_remove_files(&kdev->kobj, vlv_attrs);
 	else
-- 
2.20.1

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