[PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson@intel.com>

Check if the device is powered down prior to any engine activity,
as, on such cases, all the TLBs were already invalidated, so an
explicit TLB invalidation is not needed, thus reducing the
performance regression impact due to it.

This becomes more significant with GuC, as it can only do so when
the connection to the GuC is awake.

Cc: stable@vger.kernel.org
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 ++++++----
 drivers/gpu/drm/i915/gt/intel_gt.c        | 17 ++++++++++-------
 drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 +++
 3 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 97c820eee115..6835279943df 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -6,14 +6,15 @@
 
 #include <drm/drm_cache.h>
 
+#include "gt/intel_gt.h"
+#include "gt/intel_gt_pm.h"
+
 #include "i915_drv.h"
 #include "i915_gem_object.h"
 #include "i915_scatterlist.h"
 #include "i915_gem_lmem.h"
 #include "i915_gem_mman.h"
 
-#include "gt/intel_gt.h"
-
 void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 				 struct sg_table *pages,
 				 unsigned int sg_page_sizes)
@@ -217,10 +218,11 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 
 	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
 		struct drm_i915_private *i915 = to_i915(obj->base.dev);
+		struct intel_gt *gt = to_gt(i915);
 		intel_wakeref_t wakeref;
 
-		with_intel_runtime_pm_if_active(&i915->runtime_pm, wakeref)
-			intel_gt_invalidate_tlbs(to_gt(i915));
+		with_intel_gt_pm_if_awake(gt, wakeref)
+			intel_gt_invalidate_tlbs(gt);
 	}
 
 	return pages;
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 68c2b0d8f187..c4d43da84d8e 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -12,6 +12,7 @@
 
 #include "i915_drv.h"
 #include "intel_context.h"
+#include "intel_engine_pm.h"
 #include "intel_engine_regs.h"
 #include "intel_ggtt_gmch.h"
 #include "intel_gt.h"
@@ -924,6 +925,7 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	struct drm_i915_private *i915 = gt->i915;
 	struct intel_uncore *uncore = gt->uncore;
 	struct intel_engine_cs *engine;
+	intel_engine_mask_t awake, tmp;
 	enum intel_engine_id id;
 	const i915_reg_t *regs;
 	unsigned int num = 0;
@@ -947,26 +949,31 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 
 	GEM_TRACE("\n");
 
-	assert_rpm_wakelock_held(&i915->runtime_pm);
-
 	mutex_lock(&gt->tlb_invalidate_lock);
 	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
 
 	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
 
+	awake = 0;
 	for_each_engine(engine, gt, id) {
 		struct reg_and_bit rb;
 
+		if (!intel_engine_pm_is_awake(engine))
+			continue;
+
 		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
 		if (!i915_mmio_reg_offset(rb.reg))
 			continue;
 
 		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
+		awake |= engine->mask;
 	}
 
 	spin_unlock_irq(&uncore->lock);
 
-	for_each_engine(engine, gt, id) {
+	for_each_engine_masked(engine, gt, awake, tmp) {
+		struct reg_and_bit rb;
+
 		/*
 		 * HW architecture suggest typical invalidation time at 40us,
 		 * with pessimistic cases up to 100us and a recommendation to
@@ -974,12 +981,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 		 */
 		const unsigned int timeout_us = 100;
 		const unsigned int timeout_ms = 4;
-		struct reg_and_bit rb;
 
 		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
-		if (!i915_mmio_reg_offset(rb.reg))
-			continue;
-
 		if (__intel_wait_for_register_fw(uncore,
 						 rb.reg, rb.bit, 0,
 						 timeout_us, timeout_ms,
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
index bc898df7a48c..a334787a4939 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
@@ -55,6 +55,9 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
 	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
 	     intel_gt_pm_put(gt), tmp = 0)
 
+#define with_intel_gt_pm_if_awake(gt, wf) \
+	for (wf = intel_gt_pm_get_if_awake(gt); wf; intel_gt_pm_put_async(gt), wf = 0)
+
 static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
 {
 	return intel_wakeref_wait_for_idle(&gt->wakeref);
-- 
2.36.1

[PATCH v2 03/21] drm/i915/gt: Invalidate TLB of the OA unit at TLB invalidations

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson@intel.com>

Ensure that the TLB of the OA unit is also invalidated
on gen12 HW, as just invalidating the TLB of an engine is not
enough.

Cc: stable@vger.kernel.org
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/gt/intel_gt.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index c4d43da84d8e..1d84418e8676 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -11,6 +11,7 @@
 #include "pxp/intel_pxp.h"
 
 #include "i915_drv.h"
+#include "i915_perf_oa_regs.h"
 #include "intel_context.h"
 #include "intel_engine_pm.h"
 #include "intel_engine_regs.h"
@@ -969,6 +970,15 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 		awake |= engine->mask;
 	}
 
+	/* Wa_2207587034:tgl,dg1,rkl,adl-s,adl-p */
+	if (awake &&
+	    (IS_TIGERLAKE(i915) ||
+	     IS_DG1(i915) ||
+	     IS_ROCKETLAKE(i915) ||
+	     IS_ALDERLAKE_S(i915) ||
+	     IS_ALDERLAKE_P(i915)))
+		intel_uncore_write_fw(uncore, GEN12_OA_TLB_INV_CR, 1);
+
 	spin_unlock_irq(&uncore->lock);
 
 	for_each_engine_masked(engine, gt, awake, tmp) {
-- 
2.36.1

[PATCH v2 04/21] drm/i915/gt: Only invalidate TLBs exposed to user manipulation

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson@intel.com>

Don't flush TLBs when the buffer is only used in the GGTT under full
control of the kernel, as there's no risk of concurrent access
and stale access from prefetch.

We only need to invalidate the TLB if they are accessible by the user.
That helps to reduce the performance regression introduced by TLB
invalidate logic.

Cc: stable@vger.kernel.org
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/i915_vma.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index ef3b04c7e153..646f419b2035 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -538,7 +538,8 @@ int i915_vma_bind(struct i915_vma *vma,
 				   bind_flags);
 	}
 
-	set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
+	if (bind_flags & I915_VMA_LOCAL_BIND)
+		set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
 
 	atomic_or(bind_flags, &vma->flags);
 	return 0;
-- 
2.36.1

[PATCH v2 05/21] drm/i915/gt: Skip TLB invalidations once wedged

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson@intel.com>

Skip all further TLB invalidations once the device is wedged and
had been reset, as, on such cases, it can no longer process instructions
on the GPU and the user no longer has access to the TLB's in each engine.

That helps to reduce the performance regression introduced by TLB
invalidate logic.

Cc: stable@vger.kernel.org
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/gt/intel_gt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 1d84418e8676..5c55a90672f4 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -934,6 +934,9 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
 		return;
 
+	if (intel_gt_is_wedged(gt))
+		return;
+
 	if (GRAPHICS_VER(i915) == 12) {
 		regs = gen12_regs;
 		num = ARRAY_SIZE(gen12_regs);
-- 
2.36.1

[PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson@intel.com>

Invalidate TLB in patch, in order to reduce performance regressions.

Currently, every caller performs a full barrier around a TLB
invalidation, ignoring all other invalidations that may have already
removed their PTEs from the cache. As this is a synchronous operation
and can be quite slow, we cause multiple threads to contend on the TLB
invalidate mutex blocking userspace.

We only need to invalidate the TLB once after replacing our PTE to
ensure that there is no possible continued access to the physical
address before releasing our pages. By tracking a seqno for each full
TLB invalidate we can quickly determine if one has been performed since
rewriting the PTE, and only if necessary trigger one for ourselves.

That helps to reduce the performance regression introduced by TLB
invalidate logic.

[mchehab: rebased to not require moving the code to a separate file]

Cc: stable@vger.kernel.org
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/

 .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 +-
 drivers/gpu/drm/i915/gem/i915_gem_pages.c     | 21 +++++---
 drivers/gpu/drm/i915/gt/intel_gt.c            | 53 ++++++++++++++-----
 drivers/gpu/drm/i915/gt/intel_gt.h            | 12 ++++-
 drivers/gpu/drm/i915/gt/intel_gt_types.h      | 18 ++++++-
 drivers/gpu/drm/i915/gt/intel_ppgtt.c         |  8 ++-
 drivers/gpu/drm/i915/i915_vma.c               | 34 +++++++++---
 drivers/gpu/drm/i915/i915_vma.h               |  1 +
 drivers/gpu/drm/i915/i915_vma_resource.c      |  5 +-
 drivers/gpu/drm/i915/i915_vma_resource.h      |  6 ++-
 10 files changed, 125 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 5cf36a130061..9f6b14ec189a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -335,7 +335,6 @@ struct drm_i915_gem_object {
 #define I915_BO_READONLY          BIT(7)
 #define I915_TILING_QUIRK_BIT     8 /* unknown swizzling; do not release! */
 #define I915_BO_PROTECTED         BIT(9)
-#define I915_BO_WAS_BOUND_BIT     10
 	/**
 	 * @mem_flags - Mutable placement-related flags
 	 *
@@ -616,6 +615,8 @@ struct drm_i915_gem_object {
 		 * pages were last acquired.
 		 */
 		bool dirty:1;
+
+		u32 tlb;
 	} mm;
 
 	struct {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 6835279943df..8357dbdcab5c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -191,6 +191,18 @@ static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
 		vunmap(ptr);
 }
 
+static void flush_tlb_invalidate(struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+	struct intel_gt *gt = to_gt(i915);
+
+	if (!obj->mm.tlb)
+		return;
+
+	intel_gt_invalidate_tlb(gt, obj->mm.tlb);
+	obj->mm.tlb = 0;
+}
+
 struct sg_table *
 __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 {
@@ -216,14 +228,7 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
 	__i915_gem_object_reset_page_iter(obj);
 	obj->mm.page_sizes.phys = obj->mm.page_sizes.sg = 0;
 
-	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
-		struct drm_i915_private *i915 = to_i915(obj->base.dev);
-		struct intel_gt *gt = to_gt(i915);
-		intel_wakeref_t wakeref;
-
-		with_intel_gt_pm_if_awake(gt, wakeref)
-			intel_gt_invalidate_tlbs(gt);
-	}
+	flush_tlb_invalidate(obj);
 
 	return pages;
 }
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 5c55a90672f4..f435e06125aa 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -38,8 +38,6 @@ static void __intel_gt_init_early(struct intel_gt *gt)
 {
 	spin_lock_init(&gt->irq_lock);
 
-	mutex_init(&gt->tlb_invalidate_lock);
-
 	INIT_LIST_HEAD(&gt->closed_vma);
 	spin_lock_init(&gt->closed_lock);
 
@@ -50,6 +48,8 @@ static void __intel_gt_init_early(struct intel_gt *gt)
 	intel_gt_init_reset(gt);
 	intel_gt_init_requests(gt);
 	intel_gt_init_timelines(gt);
+	mutex_init(&gt->tlb.invalidate_lock);
+	seqcount_mutex_init(&gt->tlb.seqno, &gt->tlb.invalidate_lock);
 	intel_gt_pm_init_early(gt);
 
 	intel_uc_init_early(&gt->uc);
@@ -770,6 +770,7 @@ void intel_gt_driver_late_release_all(struct drm_i915_private *i915)
 		intel_gt_fini_requests(gt);
 		intel_gt_fini_reset(gt);
 		intel_gt_fini_timelines(gt);
+		mutex_destroy(&gt->tlb.invalidate_lock);
 		intel_engines_free(gt);
 	}
 }
@@ -908,7 +909,7 @@ get_reg_and_bit(const struct intel_engine_cs *engine, const bool gen8,
 	return rb;
 }
 
-void intel_gt_invalidate_tlbs(struct intel_gt *gt)
+static void mmio_invalidate_full(struct intel_gt *gt)
 {
 	static const i915_reg_t gen8_regs[] = {
 		[RENDER_CLASS]			= GEN8_RTCR,
@@ -931,12 +932,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	const i915_reg_t *regs;
 	unsigned int num = 0;
 
-	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
-		return;
-
-	if (intel_gt_is_wedged(gt))
-		return;
-
 	if (GRAPHICS_VER(i915) == 12) {
 		regs = gen12_regs;
 		num = ARRAY_SIZE(gen12_regs);
@@ -951,9 +946,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 			  "Platform does not implement TLB invalidation!"))
 		return;
 
-	GEM_TRACE("\n");
-
-	mutex_lock(&gt->tlb_invalidate_lock);
 	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
 
 	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
@@ -973,6 +965,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 		awake |= engine->mask;
 	}
 
+	GT_TRACE(gt, "invalidated engines %08x\n", awake);
+
 	/* Wa_2207587034:tgl,dg1,rkl,adl-s,adl-p */
 	if (awake &&
 	    (IS_TIGERLAKE(i915) ||
@@ -1012,5 +1006,38 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	 * transitions.
 	 */
 	intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL);
-	mutex_unlock(&gt->tlb_invalidate_lock);
+}
+
+static bool tlb_seqno_passed(const struct intel_gt *gt, u32 seqno)
+{
+	u32 cur = intel_gt_tlb_seqno(gt);
+
+	/* Only skip if a *full* TLB invalidate barrier has passed */
+	return (s32)(cur - ALIGN(seqno, 2)) > 0;
+}
+
+void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
+{
+	intel_wakeref_t wakeref;
+
+	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
+		return;
+
+	if (intel_gt_is_wedged(gt))
+		return;
+
+	if (tlb_seqno_passed(gt, seqno))
+		return;
+
+	with_intel_gt_pm_if_awake(gt, wakeref) {
+		mutex_lock(&gt->tlb.invalidate_lock);
+		if (tlb_seqno_passed(gt, seqno))
+			goto unlock;
+
+		mmio_invalidate_full(gt);
+
+		write_seqcount_invalidate(&gt->tlb.seqno);
+unlock:
+		mutex_unlock(&gt->tlb.invalidate_lock);
+	}
 }
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
index 82d6f248d876..40b06adf509a 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt.h
@@ -101,6 +101,16 @@ void intel_gt_info_print(const struct intel_gt_info *info,
 
 void intel_gt_watchdog_work(struct work_struct *work);
 
-void intel_gt_invalidate_tlbs(struct intel_gt *gt);
+static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt)
+{
+	return seqprop_sequence(&gt->tlb.seqno);
+}
+
+static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt)
+{
+	return intel_gt_tlb_seqno(gt) | 1;
+}
+
+void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno);
 
 #endif /* __INTEL_GT_H__ */
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
index df708802889d..3804a583382b 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
@@ -11,6 +11,7 @@
 #include <linux/llist.h>
 #include <linux/mutex.h>
 #include <linux/notifier.h>
+#include <linux/seqlock.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
@@ -83,7 +84,22 @@ struct intel_gt {
 	struct intel_uc uc;
 	struct intel_gsc gsc;
 
-	struct mutex tlb_invalidate_lock;
+	struct {
+		/* Serialize global tlb invalidations */
+		struct mutex invalidate_lock;
+
+		/*
+		 * Batch TLB invalidations
+		 *
+		 * After unbinding the PTE, we need to ensure the TLB
+		 * are invalidated prior to releasing the physical pages.
+		 * But we only need one such invalidation for all unbinds,
+		 * so we track how many TLB invalidations have been
+		 * performed since unbind the PTE and only emit an extra
+		 * invalidate if no full barrier has been passed.
+		 */
+		seqcount_mutex_t seqno;
+	} tlb;
 
 	struct i915_wa_list wa_list;
 
diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
index d8b94d638559..2da6c82a8bd2 100644
--- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
@@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
 void ppgtt_unbind_vma(struct i915_address_space *vm,
 		      struct i915_vma_resource *vma_res)
 {
-	if (vma_res->allocated)
-		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
+	if (!vma_res->allocated)
+		return;
+
+	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
+	if (vma_res->tlb)
+		vma_invalidate_tlb(vm, *vma_res->tlb);
 }
 
 static unsigned long pd_count(u64 size, int shift)
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 646f419b2035..84a9ccbc5fc5 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -538,9 +538,6 @@ int i915_vma_bind(struct i915_vma *vma,
 				   bind_flags);
 	}
 
-	if (bind_flags & I915_VMA_LOCAL_BIND)
-		set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
-
 	atomic_or(bind_flags, &vma->flags);
 	return 0;
 }
@@ -1311,6 +1308,19 @@ I915_SELFTEST_EXPORT int i915_vma_get_pages(struct i915_vma *vma)
 	return err;
 }
 
+void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb)
+{
+	/*
+	 * Before we release the pages that were bound by this vma, we
+	 * must invalidate all the TLBs that may still have a reference
+	 * back to our physical address. It only needs to be done once,
+	 * so after updating the PTE to point away from the pages, record
+	 * the most recent TLB invalidation seqno, and if we have not yet
+	 * flushed the TLBs upon release, perform a full invalidation.
+	 */
+	WRITE_ONCE(tlb, intel_gt_next_invalidate_tlb_full(vm->gt));
+}
+
 static void __vma_put_pages(struct i915_vma *vma, unsigned int count)
 {
 	/* We allocate under vma_get_pages, so beware the shrinker */
@@ -1942,7 +1952,12 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
 		vma->vm->skip_pte_rewrite;
 	trace_i915_vma_unbind(vma);
 
-	unbind_fence = i915_vma_resource_unbind(vma_res);
+	if (async)
+		unbind_fence = i915_vma_resource_unbind(vma_res,
+							&vma->obj->mm.tlb);
+	else
+		unbind_fence = i915_vma_resource_unbind(vma_res, NULL);
+
 	vma->resource = NULL;
 
 	atomic_and(~(I915_VMA_BIND_MASK | I915_VMA_ERROR | I915_VMA_GGTT_WRITE),
@@ -1950,10 +1965,13 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
 
 	i915_vma_detach(vma);
 
-	if (!async && unbind_fence) {
-		dma_fence_wait(unbind_fence, false);
-		dma_fence_put(unbind_fence);
-		unbind_fence = NULL;
+	if (!async) {
+		if (unbind_fence) {
+			dma_fence_wait(unbind_fence, false);
+			dma_fence_put(unbind_fence);
+			unbind_fence = NULL;
+		}
+		vma_invalidate_tlb(vma->vm, vma->obj->mm.tlb);
 	}
 
 	/*
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index 88ca0bd9c900..5048eed536da 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -213,6 +213,7 @@ bool i915_vma_misplaced(const struct i915_vma *vma,
 			u64 size, u64 alignment, u64 flags);
 void __i915_vma_set_map_and_fenceable(struct i915_vma *vma);
 void i915_vma_revoke_mmap(struct i915_vma *vma);
+void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb);
 struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async);
 int __i915_vma_unbind(struct i915_vma *vma);
 int __must_check i915_vma_unbind(struct i915_vma *vma);
diff --git a/drivers/gpu/drm/i915/i915_vma_resource.c b/drivers/gpu/drm/i915/i915_vma_resource.c
index 27c55027387a..5a67995ea5fe 100644
--- a/drivers/gpu/drm/i915/i915_vma_resource.c
+++ b/drivers/gpu/drm/i915/i915_vma_resource.c
@@ -223,10 +223,13 @@ i915_vma_resource_fence_notify(struct i915_sw_fence *fence,
  * Return: A refcounted pointer to a dma-fence that signals when unbinding is
  * complete.
  */
-struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res)
+struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
+					   u32 *tlb)
 {
 	struct i915_address_space *vm = vma_res->vm;
 
+	vma_res->tlb = tlb;
+
 	/* Reference for the sw fence */
 	i915_vma_resource_get(vma_res);
 
diff --git a/drivers/gpu/drm/i915/i915_vma_resource.h b/drivers/gpu/drm/i915/i915_vma_resource.h
index 5d8427caa2ba..06923d1816e7 100644
--- a/drivers/gpu/drm/i915/i915_vma_resource.h
+++ b/drivers/gpu/drm/i915/i915_vma_resource.h
@@ -67,6 +67,7 @@ struct i915_page_sizes {
  * taken when the unbind is scheduled.
  * @skip_pte_rewrite: During ggtt suspend and vm takedown pte rewriting
  * needs to be skipped for unbind.
+ * @tlb: pointer for obj->mm.tlb, if async unbind. Otherwise, NULL
  *
  * The lifetime of a struct i915_vma_resource is from a binding request to
  * the actual possible asynchronous unbind has completed.
@@ -119,6 +120,8 @@ struct i915_vma_resource {
 	bool immediate_unbind:1;
 	bool needs_wakeref:1;
 	bool skip_pte_rewrite:1;
+
+	u32 *tlb;
 };
 
 bool i915_vma_resource_hold(struct i915_vma_resource *vma_res,
@@ -131,7 +134,8 @@ struct i915_vma_resource *i915_vma_resource_alloc(void);
 
 void i915_vma_resource_free(struct i915_vma_resource *vma_res);
 
-struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res);
+struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
+					   u32 *tlb);
 
 void __i915_vma_resource_init(struct i915_vma_resource *vma_res);
 
-- 
2.36.1

Re: [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[Tvrtko Ursulin]

On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Check if the device is powered down prior to any engine activity,
> as, on such cases, all the TLBs were already invalidated, so an
> explicit TLB invalidation is not needed, thus reducing the
> performance regression impact due to it.
> 
> This becomes more significant with GuC, as it can only do so when
> the connection to the GuC is awake.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Patch itself looks fine but I don't think we closed on the issue of 
stable/fixes on this patch?

My position here is that, if the functional issue is only with GuC 
invalidations, then the tags shouldn't be there (and the huge CC list).

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>   drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 ++++++----
>   drivers/gpu/drm/i915/gt/intel_gt.c        | 17 ++++++++++-------
>   drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 +++
>   3 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 97c820eee115..6835279943df 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -6,14 +6,15 @@
>   
>   #include <drm/drm_cache.h>
>   
> +#include "gt/intel_gt.h"
> +#include "gt/intel_gt_pm.h"
> +
>   #include "i915_drv.h"
>   #include "i915_gem_object.h"
>   #include "i915_scatterlist.h"
>   #include "i915_gem_lmem.h"
>   #include "i915_gem_mman.h"
>   
> -#include "gt/intel_gt.h"
> -
>   void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
>   				 struct sg_table *pages,
>   				 unsigned int sg_page_sizes)
> @@ -217,10 +218,11 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>   
>   	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
>   		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +		struct intel_gt *gt = to_gt(i915);
>   		intel_wakeref_t wakeref;
>   
> -		with_intel_runtime_pm_if_active(&i915->runtime_pm, wakeref)
> -			intel_gt_invalidate_tlbs(to_gt(i915));
> +		with_intel_gt_pm_if_awake(gt, wakeref)
> +			intel_gt_invalidate_tlbs(gt);
>   	}
>   
>   	return pages;
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 68c2b0d8f187..c4d43da84d8e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -12,6 +12,7 @@
>   
>   #include "i915_drv.h"
>   #include "intel_context.h"
> +#include "intel_engine_pm.h"
>   #include "intel_engine_regs.h"
>   #include "intel_ggtt_gmch.h"
>   #include "intel_gt.h"
> @@ -924,6 +925,7 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	struct drm_i915_private *i915 = gt->i915;
>   	struct intel_uncore *uncore = gt->uncore;
>   	struct intel_engine_cs *engine;
> +	intel_engine_mask_t awake, tmp;
>   	enum intel_engine_id id;
>   	const i915_reg_t *regs;
>   	unsigned int num = 0;
> @@ -947,26 +949,31 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   
>   	GEM_TRACE("\n");
>   
> -	assert_rpm_wakelock_held(&i915->runtime_pm);
> -
>   	mutex_lock(&gt->tlb_invalidate_lock);
>   	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>   
>   	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
>   
> +	awake = 0;
>   	for_each_engine(engine, gt, id) {
>   		struct reg_and_bit rb;
>   
> +		if (!intel_engine_pm_is_awake(engine))
> +			continue;
> +
>   		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
>   		if (!i915_mmio_reg_offset(rb.reg))
>   			continue;
>   
>   		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
> +		awake |= engine->mask;
>   	}
>   
>   	spin_unlock_irq(&uncore->lock);
>   
> -	for_each_engine(engine, gt, id) {
> +	for_each_engine_masked(engine, gt, awake, tmp) {
> +		struct reg_and_bit rb;
> +
>   		/*
>   		 * HW architecture suggest typical invalidation time at 40us,
>   		 * with pessimistic cases up to 100us and a recommendation to
> @@ -974,12 +981,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   		 */
>   		const unsigned int timeout_us = 100;
>   		const unsigned int timeout_ms = 4;
> -		struct reg_and_bit rb;
>   
>   		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> -		if (!i915_mmio_reg_offset(rb.reg))
> -			continue;
> -
>   		if (__intel_wait_for_register_fw(uncore,
>   						 rb.reg, rb.bit, 0,
>   						 timeout_us, timeout_ms,
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> index bc898df7a48c..a334787a4939 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> @@ -55,6 +55,9 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
>   	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
>   	     intel_gt_pm_put(gt), tmp = 0)
>   
> +#define with_intel_gt_pm_if_awake(gt, wf) \
> +	for (wf = intel_gt_pm_get_if_awake(gt); wf; intel_gt_pm_put_async(gt), wf = 0)
> +
>   static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
>   {
>   	return intel_wakeref_wait_for_idle(&gt->wakeref);

Re: [PATCH v2 03/21] drm/i915/gt: Invalidate TLB of the OA unit at TLB invalidations

[Tvrtko Ursulin]

On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Ensure that the TLB of the OA unit is also invalidated
> on gen12 HW, as just invalidating the TLB of an engine is not
> enough.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>   drivers/gpu/drm/i915/gt/intel_gt.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index c4d43da84d8e..1d84418e8676 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -11,6 +11,7 @@
>   #include "pxp/intel_pxp.h"
>   
>   #include "i915_drv.h"
> +#include "i915_perf_oa_regs.h"
>   #include "intel_context.h"
>   #include "intel_engine_pm.h"
>   #include "intel_engine_regs.h"
> @@ -969,6 +970,15 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   		awake |= engine->mask;
>   	}
>   
> +	/* Wa_2207587034:tgl,dg1,rkl,adl-s,adl-p */
> +	if (awake &&
> +	    (IS_TIGERLAKE(i915) ||
> +	     IS_DG1(i915) ||
> +	     IS_ROCKETLAKE(i915) ||
> +	     IS_ALDERLAKE_S(i915) ||
> +	     IS_ALDERLAKE_P(i915)))
> +		intel_uncore_write_fw(uncore, GEN12_OA_TLB_INV_CR, 1);
> +
>   	spin_unlock_irq(&uncore->lock);
>   
>   	for_each_engine_masked(engine, gt, awake, tmp) {

Re: [PATCH v2 04/21] drm/i915/gt: Only invalidate TLBs exposed to user manipulation

[Tvrtko Ursulin]

On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Don't flush TLBs when the buffer is only used in the GGTT under full
> control of the kernel, as there's no risk of concurrent access
> and stale access from prefetch.
> 
> We only need to invalidate the TLB if they are accessible by the user.
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Do we really need or want stable and fixes on this one?

What do we think the performance improvement is, given there's very 
little in GGTT, which is not mapped via PPGTT as well?

I think it is safe, but part of me would ideally not even want to think 
about whether it is safe, if the performance improvement is 
non-existent. Which I can't imagine how there would be?

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>   drivers/gpu/drm/i915/i915_vma.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index ef3b04c7e153..646f419b2035 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -538,7 +538,8 @@ int i915_vma_bind(struct i915_vma *vma,
>   				   bind_flags);
>   	}
>   
> -	set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
> +	if (bind_flags & I915_VMA_LOCAL_BIND)
> +		set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
>   
>   	atomic_or(bind_flags, &vma->flags);
>   	return 0;

Re: [PATCH v2 05/21] drm/i915/gt: Skip TLB invalidations once wedged

[Tvrtko Ursulin]

On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Skip all further TLB invalidations once the device is wedged and
> had been reset, as, on such cases, it can no longer process instructions
> on the GPU and the user no longer has access to the TLB's in each engine.
> 
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Is the claim of a performance regression this solved based on a wedged 
GPU which does not work any more to the extend where mmio tlb 
invalidation requests keep timing out? If so please clarify in the 
commit text and then it looks good to me. Even if it is IMO a very 
borderline situation to declare something a fix.

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>   drivers/gpu/drm/i915/gt/intel_gt.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 1d84418e8676..5c55a90672f4 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -934,6 +934,9 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
>   		return;
>   
> +	if (intel_gt_is_wedged(gt))
> +		return;
> +
>   	if (GRAPHICS_VER(i915) == 12) {
>   		regs = gen12_regs;
>   		num = ARRAY_SIZE(gen12_regs);

Re: [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Tvrtko Ursulin]

On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Invalidate TLB in patch, in order to reduce performance regressions.

"in batches"?

> Currently, every caller performs a full barrier around a TLB
> invalidation, ignoring all other invalidations that may have already
> removed their PTEs from the cache. As this is a synchronous operation
> and can be quite slow, we cause multiple threads to contend on the TLB
> invalidate mutex blocking userspace.
> 
> We only need to invalidate the TLB once after replacing our PTE to
> ensure that there is no possible continued access to the physical
> address before releasing our pages. By tracking a seqno for each full
> TLB invalidate we can quickly determine if one has been performed since
> rewriting the PTE, and only if necessary trigger one for ourselves.
> 
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
> 
> [mchehab: rebased to not require moving the code to a separate file]
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>   .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 +-
>   drivers/gpu/drm/i915/gem/i915_gem_pages.c     | 21 +++++---
>   drivers/gpu/drm/i915/gt/intel_gt.c            | 53 ++++++++++++++-----
>   drivers/gpu/drm/i915/gt/intel_gt.h            | 12 ++++-
>   drivers/gpu/drm/i915/gt/intel_gt_types.h      | 18 ++++++-
>   drivers/gpu/drm/i915/gt/intel_ppgtt.c         |  8 ++-
>   drivers/gpu/drm/i915/i915_vma.c               | 34 +++++++++---
>   drivers/gpu/drm/i915/i915_vma.h               |  1 +
>   drivers/gpu/drm/i915/i915_vma_resource.c      |  5 +-
>   drivers/gpu/drm/i915/i915_vma_resource.h      |  6 ++-
>   10 files changed, 125 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> index 5cf36a130061..9f6b14ec189a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -335,7 +335,6 @@ struct drm_i915_gem_object {
>   #define I915_BO_READONLY          BIT(7)
>   #define I915_TILING_QUIRK_BIT     8 /* unknown swizzling; do not release! */
>   #define I915_BO_PROTECTED         BIT(9)
> -#define I915_BO_WAS_BOUND_BIT     10
>   	/**
>   	 * @mem_flags - Mutable placement-related flags
>   	 *
> @@ -616,6 +615,8 @@ struct drm_i915_gem_object {
>   		 * pages were last acquired.
>   		 */
>   		bool dirty:1;
> +
> +		u32 tlb;
>   	} mm;
>   
>   	struct {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 6835279943df..8357dbdcab5c 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -191,6 +191,18 @@ static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
>   		vunmap(ptr);
>   }
>   
> +static void flush_tlb_invalidate(struct drm_i915_gem_object *obj)
> +{
> +	struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +	struct intel_gt *gt = to_gt(i915);
> +
> +	if (!obj->mm.tlb)
> +		return;
> +
> +	intel_gt_invalidate_tlb(gt, obj->mm.tlb);
> +	obj->mm.tlb = 0;
> +}
> +
>   struct sg_table *
>   __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>   {
> @@ -216,14 +228,7 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>   	__i915_gem_object_reset_page_iter(obj);
>   	obj->mm.page_sizes.phys = obj->mm.page_sizes.sg = 0;
>   
> -	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
> -		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> -		struct intel_gt *gt = to_gt(i915);
> -		intel_wakeref_t wakeref;
> -
> -		with_intel_gt_pm_if_awake(gt, wakeref)
> -			intel_gt_invalidate_tlbs(gt);
> -	}
> +	flush_tlb_invalidate(obj);
>   
>   	return pages;
>   }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 5c55a90672f4..f435e06125aa 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -38,8 +38,6 @@ static void __intel_gt_init_early(struct intel_gt *gt)
>   {
>   	spin_lock_init(&gt->irq_lock);
>   
> -	mutex_init(&gt->tlb_invalidate_lock);
> -
>   	INIT_LIST_HEAD(&gt->closed_vma);
>   	spin_lock_init(&gt->closed_lock);
>   
> @@ -50,6 +48,8 @@ static void __intel_gt_init_early(struct intel_gt *gt)
>   	intel_gt_init_reset(gt);
>   	intel_gt_init_requests(gt);
>   	intel_gt_init_timelines(gt);
> +	mutex_init(&gt->tlb.invalidate_lock);
> +	seqcount_mutex_init(&gt->tlb.seqno, &gt->tlb.invalidate_lock);
>   	intel_gt_pm_init_early(gt);
>   
>   	intel_uc_init_early(&gt->uc);
> @@ -770,6 +770,7 @@ void intel_gt_driver_late_release_all(struct drm_i915_private *i915)
>   		intel_gt_fini_requests(gt);
>   		intel_gt_fini_reset(gt);
>   		intel_gt_fini_timelines(gt);
> +		mutex_destroy(&gt->tlb.invalidate_lock);
>   		intel_engines_free(gt);
>   	}
>   }
> @@ -908,7 +909,7 @@ get_reg_and_bit(const struct intel_engine_cs *engine, const bool gen8,
>   	return rb;
>   }
>   
> -void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> +static void mmio_invalidate_full(struct intel_gt *gt)
>   {
>   	static const i915_reg_t gen8_regs[] = {
>   		[RENDER_CLASS]			= GEN8_RTCR,
> @@ -931,12 +932,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	const i915_reg_t *regs;
>   	unsigned int num = 0;
>   
> -	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
> -		return;
> -
> -	if (intel_gt_is_wedged(gt))
> -		return;
> -
>   	if (GRAPHICS_VER(i915) == 12) {
>   		regs = gen12_regs;
>   		num = ARRAY_SIZE(gen12_regs);
> @@ -951,9 +946,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   			  "Platform does not implement TLB invalidation!"))
>   		return;
>   
> -	GEM_TRACE("\n");
> -
> -	mutex_lock(&gt->tlb_invalidate_lock);
>   	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>   
>   	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
> @@ -973,6 +965,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   		awake |= engine->mask;
>   	}
>   
> +	GT_TRACE(gt, "invalidated engines %08x\n", awake);
> +
>   	/* Wa_2207587034:tgl,dg1,rkl,adl-s,adl-p */
>   	if (awake &&
>   	    (IS_TIGERLAKE(i915) ||
> @@ -1012,5 +1006,38 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	 * transitions.
>   	 */
>   	intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL);
> -	mutex_unlock(&gt->tlb_invalidate_lock);
> +}
> +
> +static bool tlb_seqno_passed(const struct intel_gt *gt, u32 seqno)
> +{
> +	u32 cur = intel_gt_tlb_seqno(gt);
> +
> +	/* Only skip if a *full* TLB invalidate barrier has passed */
> +	return (s32)(cur - ALIGN(seqno, 2)) > 0;
> +}
> +
> +void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
> +{
> +	intel_wakeref_t wakeref;
> +
> +	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
> +		return;
> +
> +	if (intel_gt_is_wedged(gt))
> +		return;
> +
> +	if (tlb_seqno_passed(gt, seqno))
> +		return;
> +
> +	with_intel_gt_pm_if_awake(gt, wakeref) {
> +		mutex_lock(&gt->tlb.invalidate_lock);
> +		if (tlb_seqno_passed(gt, seqno))
> +			goto unlock;
> +
> +		mmio_invalidate_full(gt);
> +
> +		write_seqcount_invalidate(&gt->tlb.seqno);
> +unlock:
> +		mutex_unlock(&gt->tlb.invalidate_lock);
> +	}
>   }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
> index 82d6f248d876..40b06adf509a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.h
> @@ -101,6 +101,16 @@ void intel_gt_info_print(const struct intel_gt_info *info,
>   
>   void intel_gt_watchdog_work(struct work_struct *work);
>   
> -void intel_gt_invalidate_tlbs(struct intel_gt *gt);
> +static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt)
> +{
> +	return seqprop_sequence(&gt->tlb.seqno);
> +}
> +
> +static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt)
> +{
> +	return intel_gt_tlb_seqno(gt) | 1;
> +}
> +
> +void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno);
>   
>   #endif /* __INTEL_GT_H__ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> index df708802889d..3804a583382b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> @@ -11,6 +11,7 @@
>   #include <linux/llist.h>
>   #include <linux/mutex.h>
>   #include <linux/notifier.h>
> +#include <linux/seqlock.h>
>   #include <linux/spinlock.h>
>   #include <linux/types.h>
>   #include <linux/workqueue.h>
> @@ -83,7 +84,22 @@ struct intel_gt {
>   	struct intel_uc uc;
>   	struct intel_gsc gsc;
>   
> -	struct mutex tlb_invalidate_lock;
> +	struct {
> +		/* Serialize global tlb invalidations */
> +		struct mutex invalidate_lock;
> +
> +		/*
> +		 * Batch TLB invalidations
> +		 *
> +		 * After unbinding the PTE, we need to ensure the TLB
> +		 * are invalidated prior to releasing the physical pages.
> +		 * But we only need one such invalidation for all unbinds,
> +		 * so we track how many TLB invalidations have been
> +		 * performed since unbind the PTE and only emit an extra
> +		 * invalidate if no full barrier has been passed.
> +		 */
> +		seqcount_mutex_t seqno;
> +	} tlb;
>   
>   	struct i915_wa_list wa_list;
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> index d8b94d638559..2da6c82a8bd2 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
>   void ppgtt_unbind_vma(struct i915_address_space *vm,
>   		      struct i915_vma_resource *vma_res)
>   {
> -	if (vma_res->allocated)
> -		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> +	if (!vma_res->allocated)
> +		return;
> +
> +	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> +	if (vma_res->tlb)
> +		vma_invalidate_tlb(vm, *vma_res->tlb);

The patch is about more than batching? If there is a security hole in 
this area (unbind) with the current code?

Regards,

Tvrtko

>   }
>   
>   static unsigned long pd_count(u64 size, int shift)
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 646f419b2035..84a9ccbc5fc5 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -538,9 +538,6 @@ int i915_vma_bind(struct i915_vma *vma,
>   				   bind_flags);
>   	}
>   
> -	if (bind_flags & I915_VMA_LOCAL_BIND)
> -		set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
> -
>   	atomic_or(bind_flags, &vma->flags);
>   	return 0;
>   }
> @@ -1311,6 +1308,19 @@ I915_SELFTEST_EXPORT int i915_vma_get_pages(struct i915_vma *vma)
>   	return err;
>   }
>   
> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb)
> +{
> +	/*
> +	 * Before we release the pages that were bound by this vma, we
> +	 * must invalidate all the TLBs that may still have a reference
> +	 * back to our physical address. It only needs to be done once,
> +	 * so after updating the PTE to point away from the pages, record
> +	 * the most recent TLB invalidation seqno, and if we have not yet
> +	 * flushed the TLBs upon release, perform a full invalidation.
> +	 */
> +	WRITE_ONCE(tlb, intel_gt_next_invalidate_tlb_full(vm->gt));
> +}
> +
>   static void __vma_put_pages(struct i915_vma *vma, unsigned int count)
>   {
>   	/* We allocate under vma_get_pages, so beware the shrinker */
> @@ -1942,7 +1952,12 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
>   		vma->vm->skip_pte_rewrite;
>   	trace_i915_vma_unbind(vma);
>   
> -	unbind_fence = i915_vma_resource_unbind(vma_res);
> +	if (async)
> +		unbind_fence = i915_vma_resource_unbind(vma_res,
> +							&vma->obj->mm.tlb);
> +	else
> +		unbind_fence = i915_vma_resource_unbind(vma_res, NULL);
> +
>   	vma->resource = NULL;
>   
>   	atomic_and(~(I915_VMA_BIND_MASK | I915_VMA_ERROR | I915_VMA_GGTT_WRITE),
> @@ -1950,10 +1965,13 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
>   
>   	i915_vma_detach(vma);
>   
> -	if (!async && unbind_fence) {
> -		dma_fence_wait(unbind_fence, false);
> -		dma_fence_put(unbind_fence);
> -		unbind_fence = NULL;
> +	if (!async) {
> +		if (unbind_fence) {
> +			dma_fence_wait(unbind_fence, false);
> +			dma_fence_put(unbind_fence);
> +			unbind_fence = NULL;
> +		}
> +		vma_invalidate_tlb(vma->vm, vma->obj->mm.tlb);
>   	}
>   
>   	/*
> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
> index 88ca0bd9c900..5048eed536da 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -213,6 +213,7 @@ bool i915_vma_misplaced(const struct i915_vma *vma,
>   			u64 size, u64 alignment, u64 flags);
>   void __i915_vma_set_map_and_fenceable(struct i915_vma *vma);
>   void i915_vma_revoke_mmap(struct i915_vma *vma);
> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb);
>   struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async);
>   int __i915_vma_unbind(struct i915_vma *vma);
>   int __must_check i915_vma_unbind(struct i915_vma *vma);
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.c b/drivers/gpu/drm/i915/i915_vma_resource.c
> index 27c55027387a..5a67995ea5fe 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.c
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.c
> @@ -223,10 +223,13 @@ i915_vma_resource_fence_notify(struct i915_sw_fence *fence,
>    * Return: A refcounted pointer to a dma-fence that signals when unbinding is
>    * complete.
>    */
> -struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res)
> +struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
> +					   u32 *tlb)
>   {
>   	struct i915_address_space *vm = vma_res->vm;
>   
> +	vma_res->tlb = tlb;
> +
>   	/* Reference for the sw fence */
>   	i915_vma_resource_get(vma_res);
>   
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.h b/drivers/gpu/drm/i915/i915_vma_resource.h
> index 5d8427caa2ba..06923d1816e7 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.h
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.h
> @@ -67,6 +67,7 @@ struct i915_page_sizes {
>    * taken when the unbind is scheduled.
>    * @skip_pte_rewrite: During ggtt suspend and vm takedown pte rewriting
>    * needs to be skipped for unbind.
> + * @tlb: pointer for obj->mm.tlb, if async unbind. Otherwise, NULL
>    *
>    * The lifetime of a struct i915_vma_resource is from a binding request to
>    * the actual possible asynchronous unbind has completed.
> @@ -119,6 +120,8 @@ struct i915_vma_resource {
>   	bool immediate_unbind:1;
>   	bool needs_wakeref:1;
>   	bool skip_pte_rewrite:1;
> +
> +	u32 *tlb;
>   };
>   
>   bool i915_vma_resource_hold(struct i915_vma_resource *vma_res,
> @@ -131,7 +134,8 @@ struct i915_vma_resource *i915_vma_resource_alloc(void);
>   
>   void i915_vma_resource_free(struct i915_vma_resource *vma_res);
>   
> -struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res);
> +struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
> +					   u32 *tlb);
>   
>   void __i915_vma_resource_init(struct i915_vma_resource *vma_res);
>   

Re: [Intel-gfx] [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[Mauro Carvalho Chehab]

On Mon, 18 Jul 2022 14:16:10 +0100
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:

> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> > From: Chris Wilson <chris.p.wilson@intel.com>
> > 
> > Check if the device is powered down prior to any engine activity,
> > as, on such cases, all the TLBs were already invalidated, so an
> > explicit TLB invalidation is not needed, thus reducing the
> > performance regression impact due to it.
> > 
> > This becomes more significant with GuC, as it can only do so when
> > the connection to the GuC is awake.
> > 
> > Cc: stable@vger.kernel.org
> > Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")  
> 
> Patch itself looks fine but I don't think we closed on the issue of 
> stable/fixes on this patch?

No, because TLB cache invalidation takes time and causes time outs, which
in turn affects applications and produce Kernel warnings.

There's even open bugs due to TLB timeouts, like this one:

	[424.370996] i915 0000:00:02.0: [drm] *ERROR* rcs0 TLB invalidation did not complete in 4ms!

See:
	https://gitlab.freedesktop.org/drm/intel/-/issues/6424

So, while this is a performance regression, it ends causing a
functional regression.

The first part of this series (patches 1-7) are meant to reduce the
risk of such timeouts by doing TLB invalidation in batch and only 
when really needed (userspace-exposed TLBs for GTs that are powered-on
and non-edged).

As they're fixing such regressions, it makes sense c/c stable and having
a fixes tag.

> My position here is that, if the functional issue is only with GuC 
> invalidations, then the tags shouldn't be there (and the huge CC list).
> 
> Regards,
> 
> Tvrtko
> 
> > Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> > Cc: Fei Yang <fei.yang@intel.com>
> > Cc: Andi Shyti <andi.shyti@linux.intel.com>
> > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> > ---
> > 
> > To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> > See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> > 
> >   drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 ++++++----
> >   drivers/gpu/drm/i915/gt/intel_gt.c        | 17 ++++++++++-------
> >   drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 +++
> >   3 files changed, 19 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > index 97c820eee115..6835279943df 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> > @@ -6,14 +6,15 @@
> >   
> >   #include <drm/drm_cache.h>
> >   
> > +#include "gt/intel_gt.h"
> > +#include "gt/intel_gt_pm.h"
> > +
> >   #include "i915_drv.h"
> >   #include "i915_gem_object.h"
> >   #include "i915_scatterlist.h"
> >   #include "i915_gem_lmem.h"
> >   #include "i915_gem_mman.h"
> >   
> > -#include "gt/intel_gt.h"
> > -
> >   void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
> >   				 struct sg_table *pages,
> >   				 unsigned int sg_page_sizes)
> > @@ -217,10 +218,11 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
> >   
> >   	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
> >   		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> > +		struct intel_gt *gt = to_gt(i915);
> >   		intel_wakeref_t wakeref;
> >   
> > -		with_intel_runtime_pm_if_active(&i915->runtime_pm, wakeref)
> > -			intel_gt_invalidate_tlbs(to_gt(i915));
> > +		with_intel_gt_pm_if_awake(gt, wakeref)
> > +			intel_gt_invalidate_tlbs(gt);
> >   	}
> >   
> >   	return pages;
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> > index 68c2b0d8f187..c4d43da84d8e 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> > @@ -12,6 +12,7 @@
> >   
> >   #include "i915_drv.h"
> >   #include "intel_context.h"
> > +#include "intel_engine_pm.h"
> >   #include "intel_engine_regs.h"
> >   #include "intel_ggtt_gmch.h"
> >   #include "intel_gt.h"
> > @@ -924,6 +925,7 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> >   	struct drm_i915_private *i915 = gt->i915;
> >   	struct intel_uncore *uncore = gt->uncore;
> >   	struct intel_engine_cs *engine;
> > +	intel_engine_mask_t awake, tmp;
> >   	enum intel_engine_id id;
> >   	const i915_reg_t *regs;
> >   	unsigned int num = 0;
> > @@ -947,26 +949,31 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> >   
> >   	GEM_TRACE("\n");
> >   
> > -	assert_rpm_wakelock_held(&i915->runtime_pm);
> > -
> >   	mutex_lock(&gt->tlb_invalidate_lock);
> >   	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
> >   
> >   	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
> >   
> > +	awake = 0;
> >   	for_each_engine(engine, gt, id) {
> >   		struct reg_and_bit rb;
> >   
> > +		if (!intel_engine_pm_is_awake(engine))
> > +			continue;
> > +
> >   		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> >   		if (!i915_mmio_reg_offset(rb.reg))
> >   			continue;
> >   
> >   		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
> > +		awake |= engine->mask;
> >   	}
> >   
> >   	spin_unlock_irq(&uncore->lock);
> >   
> > -	for_each_engine(engine, gt, id) {
> > +	for_each_engine_masked(engine, gt, awake, tmp) {
> > +		struct reg_and_bit rb;
> > +
> >   		/*
> >   		 * HW architecture suggest typical invalidation time at 40us,
> >   		 * with pessimistic cases up to 100us and a recommendation to
> > @@ -974,12 +981,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> >   		 */
> >   		const unsigned int timeout_us = 100;
> >   		const unsigned int timeout_ms = 4;
> > -		struct reg_and_bit rb;
> >   
> >   		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> > -		if (!i915_mmio_reg_offset(rb.reg))
> > -			continue;
> > -
> >   		if (__intel_wait_for_register_fw(uncore,
> >   						 rb.reg, rb.bit, 0,
> >   						 timeout_us, timeout_ms,
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > index bc898df7a48c..a334787a4939 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > @@ -55,6 +55,9 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
> >   	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
> >   	     intel_gt_pm_put(gt), tmp = 0)
> >   
> > +#define with_intel_gt_pm_if_awake(gt, wf) \
> > +	for (wf = intel_gt_pm_get_if_awake(gt); wf; intel_gt_pm_put_async(gt), wf = 0)
> > +
> >   static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
> >   {
> >   	return intel_wakeref_wait_for_idle(&gt->wakeref);  

Re: [Intel-gfx] [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[Tvrtko Ursulin]

On 18/07/2022 15:53, Mauro Carvalho Chehab wrote:
> On Mon, 18 Jul 2022 14:16:10 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
>> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
>>> From: Chris Wilson <chris.p.wilson@intel.com>
>>>
>>> Check if the device is powered down prior to any engine activity,
>>> as, on such cases, all the TLBs were already invalidated, so an
>>> explicit TLB invalidation is not needed, thus reducing the
>>> performance regression impact due to it.
>>>
>>> This becomes more significant with GuC, as it can only do so when
>>> the connection to the GuC is awake.
>>>
>>> Cc: stable@vger.kernel.org
>>> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
>>
>> Patch itself looks fine but I don't think we closed on the issue of
>> stable/fixes on this patch?
> 
> No, because TLB cache invalidation takes time and causes time outs, which
> in turn affects applications and produce Kernel warnings.
> 
> There's even open bugs due to TLB timeouts, like this one:
> 
> 	[424.370996] i915 0000:00:02.0: [drm] *ERROR* rcs0 TLB invalidation did not complete in 4ms!
> 
> See:
> 	https://gitlab.freedesktop.org/drm/intel/-/issues/6424
> 
> So, while this is a performance regression, it ends causing a
> functional regression.

This test is not even particularly stressful. Fair enough - thanks for 
the information.

Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Is skipping of the ggtt only bound flush the fix for this particular test?

Regards,

Tvrtko

> 
> The first part of this series (patches 1-7) are meant to reduce the
> risk of such timeouts by doing TLB invalidation in batch and only
> when really needed (userspace-exposed TLBs for GTs that are powered-on
> and non-edged).
> 
> As they're fixing such regressions, it makes sense c/c stable and having
> a fixes tag.
> 
>> My position here is that, if the functional issue is only with GuC
>> invalidations, then the tags shouldn't be there (and the huge CC list).
>>
>> Regards,
>>
>> Tvrtko
>>
>>> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
>>> Cc: Fei Yang <fei.yang@intel.com>
>>> Cc: Andi Shyti <andi.shyti@linux.intel.com>
>>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
>>> ---
>>>
>>> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
>>> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
>>>
>>>    drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 ++++++----
>>>    drivers/gpu/drm/i915/gt/intel_gt.c        | 17 ++++++++++-------
>>>    drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 +++
>>>    3 files changed, 19 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>>> index 97c820eee115..6835279943df 100644
>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>>> @@ -6,14 +6,15 @@
>>>    
>>>    #include <drm/drm_cache.h>
>>>    
>>> +#include "gt/intel_gt.h"
>>> +#include "gt/intel_gt_pm.h"
>>> +
>>>    #include "i915_drv.h"
>>>    #include "i915_gem_object.h"
>>>    #include "i915_scatterlist.h"
>>>    #include "i915_gem_lmem.h"
>>>    #include "i915_gem_mman.h"
>>>    
>>> -#include "gt/intel_gt.h"
>>> -
>>>    void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
>>>    				 struct sg_table *pages,
>>>    				 unsigned int sg_page_sizes)
>>> @@ -217,10 +218,11 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>>>    
>>>    	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
>>>    		struct drm_i915_private *i915 = to_i915(obj->base.dev);
>>> +		struct intel_gt *gt = to_gt(i915);
>>>    		intel_wakeref_t wakeref;
>>>    
>>> -		with_intel_runtime_pm_if_active(&i915->runtime_pm, wakeref)
>>> -			intel_gt_invalidate_tlbs(to_gt(i915));
>>> +		with_intel_gt_pm_if_awake(gt, wakeref)
>>> +			intel_gt_invalidate_tlbs(gt);
>>>    	}
>>>    
>>>    	return pages;
>>> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
>>> index 68c2b0d8f187..c4d43da84d8e 100644
>>> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
>>> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
>>> @@ -12,6 +12,7 @@
>>>    
>>>    #include "i915_drv.h"
>>>    #include "intel_context.h"
>>> +#include "intel_engine_pm.h"
>>>    #include "intel_engine_regs.h"
>>>    #include "intel_ggtt_gmch.h"
>>>    #include "intel_gt.h"
>>> @@ -924,6 +925,7 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>>>    	struct drm_i915_private *i915 = gt->i915;
>>>    	struct intel_uncore *uncore = gt->uncore;
>>>    	struct intel_engine_cs *engine;
>>> +	intel_engine_mask_t awake, tmp;
>>>    	enum intel_engine_id id;
>>>    	const i915_reg_t *regs;
>>>    	unsigned int num = 0;
>>> @@ -947,26 +949,31 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>>>    
>>>    	GEM_TRACE("\n");
>>>    
>>> -	assert_rpm_wakelock_held(&i915->runtime_pm);
>>> -
>>>    	mutex_lock(&gt->tlb_invalidate_lock);
>>>    	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>>>    
>>>    	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
>>>    
>>> +	awake = 0;
>>>    	for_each_engine(engine, gt, id) {
>>>    		struct reg_and_bit rb;
>>>    
>>> +		if (!intel_engine_pm_is_awake(engine))
>>> +			continue;
>>> +
>>>    		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
>>>    		if (!i915_mmio_reg_offset(rb.reg))
>>>    			continue;
>>>    
>>>    		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
>>> +		awake |= engine->mask;
>>>    	}
>>>    
>>>    	spin_unlock_irq(&uncore->lock);
>>>    
>>> -	for_each_engine(engine, gt, id) {
>>> +	for_each_engine_masked(engine, gt, awake, tmp) {
>>> +		struct reg_and_bit rb;
>>> +
>>>    		/*
>>>    		 * HW architecture suggest typical invalidation time at 40us,
>>>    		 * with pessimistic cases up to 100us and a recommendation to
>>> @@ -974,12 +981,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>>>    		 */
>>>    		const unsigned int timeout_us = 100;
>>>    		const unsigned int timeout_ms = 4;
>>> -		struct reg_and_bit rb;
>>>    
>>>    		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
>>> -		if (!i915_mmio_reg_offset(rb.reg))
>>> -			continue;
>>> -
>>>    		if (__intel_wait_for_register_fw(uncore,
>>>    						 rb.reg, rb.bit, 0,
>>>    						 timeout_us, timeout_ms,
>>> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
>>> index bc898df7a48c..a334787a4939 100644
>>> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
>>> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
>>> @@ -55,6 +55,9 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
>>>    	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
>>>    	     intel_gt_pm_put(gt), tmp = 0)
>>>    
>>> +#define with_intel_gt_pm_if_awake(gt, wf) \
>>> +	for (wf = intel_gt_pm_get_if_awake(gt); wf; intel_gt_pm_put_async(gt), wf = 0)
>>> +
>>>    static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
>>>    {
>>>    	return intel_wakeref_wait_for_idle(&gt->wakeref);

RE: [Intel-gfx] [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[David Laight]

From: Mauro Carvalho Chehab
> Sent: 18 July 2022 15:54
> 
> On Mon, 18 Jul 2022 14:16:10 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
> > On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> > > From: Chris Wilson <chris.p.wilson@intel.com>
> > >
> > > Check if the device is powered down prior to any engine activity,
> > > as, on such cases, all the TLBs were already invalidated, so an
> > > explicit TLB invalidation is not needed, thus reducing the
> > > performance regression impact due to it.
> > >
> > > This becomes more significant with GuC, as it can only do so when
> > > the connection to the GuC is awake.
> > >
> > > Cc: stable@vger.kernel.org
> > > Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> >
> > Patch itself looks fine but I don't think we closed on the issue of
> > stable/fixes on this patch?
> 
> No, because TLB cache invalidation takes time and causes time outs, which
> in turn affects applications and produce Kernel warnings.

It's not only the TLB flushes that cause grief.

There is a loop that forces a write-back of all the frame buffer pages.
With a large display and some cpu (like my Ivy bridge one) that
takes long enough with pre-emption disabled that wakeup of RT processes
(and any pinned to the cpu) takes far longer than one might have
wished for.

Since some X servers request a flush every few seconds this makes
the system unusable for some workloads.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [Intel-gfx] [PATCH v2 04/21] drm/i915/gt: Only invalidate TLBs exposed to user manipulation

[Mauro Carvalho Chehab]

On Mon, 18 Jul 2022 14:39:17 +0100
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:

> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> > From: Chris Wilson <chris.p.wilson@intel.com>
> > 
> > Don't flush TLBs when the buffer is only used in the GGTT under full
> > control of the kernel, as there's no risk of concurrent access
> > and stale access from prefetch.
> > 
> > We only need to invalidate the TLB if they are accessible by the user.
> > That helps to reduce the performance regression introduced by TLB
> > invalidate logic.
> > 
> > Cc: stable@vger.kernel.org
> > Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")  
> 
> Do we really need or want stable and fixes on this one?
> 
> What do we think the performance improvement is, given there's very 
> little in GGTT, which is not mapped via PPGTT as well?
> 
> I think it is safe, but part of me would ideally not even want to think 
> about whether it is safe, if the performance improvement is 
> non-existent. Which I can't imagine how there would be?

Makes sense. Patch 6 actually ends removing the code doing
that, so I'll just fold this patch with patch 6, in order to
avoid adding something that will later be removed.

Regards,
Mauro

Re: [Intel-gfx] [PATCH v2 05/21] drm/i915/gt: Skip TLB invalidations once wedged

[Mauro Carvalho Chehab]

On Mon, 18 Jul 2022 14:45:22 +0100
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:

> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> > From: Chris Wilson <chris.p.wilson@intel.com>
> > 
> > Skip all further TLB invalidations once the device is wedged and
> > had been reset, as, on such cases, it can no longer process instructions
> > on the GPU and the user no longer has access to the TLB's in each engine.
> > 
> > That helps to reduce the performance regression introduced by TLB
> > invalidate logic.
> > 
> > Cc: stable@vger.kernel.org
> > Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")  
> 
> Is the claim of a performance regression this solved based on a wedged 
> GPU which does not work any more to the extend where mmio tlb 
> invalidation requests keep timing out? If so please clarify in the 
> commit text and then it looks good to me. Even if it is IMO a very 
> borderline situation to declare something a fix.

Indeed this helps on a borderline situation: if GT is wedged, TLB 
invalidation will timeout, so it makes sense to keep the patch with a
comment like:

    drm/i915/gt: Skip TLB invalidations once wedged
    
    Skip all further TLB invalidations once the device is wedged and
    had been reset, as, on such cases, it can no longer process instructions
    on the GPU and the user no longer has access to the TLB's in each engine.
    
    So, an attempt to do a TLB cache invalidation will produce a timeout.
    
    That helps to reduce the performance regression introduced by TLB
    invalidate logic.

Regards,
Mauro

Re: [Intel-gfx] [PATCH v2 05/21] drm/i915/gt: Skip TLB invalidations once wedged

[Tvrtko Ursulin]

On 18/07/2022 17:06, Mauro Carvalho Chehab wrote:
> On Mon, 18 Jul 2022 14:45:22 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
>> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
>>> From: Chris Wilson <chris.p.wilson@intel.com>
>>>
>>> Skip all further TLB invalidations once the device is wedged and
>>> had been reset, as, on such cases, it can no longer process instructions
>>> on the GPU and the user no longer has access to the TLB's in each engine.
>>>
>>> That helps to reduce the performance regression introduced by TLB
>>> invalidate logic.
>>>
>>> Cc: stable@vger.kernel.org
>>> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
>>
>> Is the claim of a performance regression this solved based on a wedged
>> GPU which does not work any more to the extend where mmio tlb
>> invalidation requests keep timing out? If so please clarify in the
>> commit text and then it looks good to me. Even if it is IMO a very
>> borderline situation to declare something a fix.
> 
> Indeed this helps on a borderline situation: if GT is wedged, TLB
> invalidation will timeout, so it makes sense to keep the patch with a
> comment like:
> 
>      drm/i915/gt: Skip TLB invalidations once wedged
>      
>      Skip all further TLB invalidations once the device is wedged and
>      had been reset, as, on such cases, it can no longer process instructions
>      on the GPU and the user no longer has access to the TLB's in each engine.
>      
>      So, an attempt to do a TLB cache invalidation will produce a timeout.
>      
>      That helps to reduce the performance regression introduced by TLB
>      invalidate logic.

Yeah that is better but whether bothering stable with it is the 
question. Wedged GPU means constant endless -EIO to userspace so very 
hard to imagine that after a TLB invalidation timeout or two there would 
be further ones. But okay, it's tiny so fine I guess.

Regards,

Tvrtko

Re: [Intel-gfx] [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[Tvrtko Ursulin]

Hi David,

On 18/07/2022 16:50, David Laight wrote:
> From: Mauro Carvalho Chehab
>> Sent: 18 July 2022 15:54
>>
>> On Mon, 18 Jul 2022 14:16:10 +0100
>> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
>>
>>> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
>>>> From: Chris Wilson <chris.p.wilson@intel.com>
>>>>
>>>> Check if the device is powered down prior to any engine activity,
>>>> as, on such cases, all the TLBs were already invalidated, so an
>>>> explicit TLB invalidation is not needed, thus reducing the
>>>> performance regression impact due to it.
>>>>
>>>> This becomes more significant with GuC, as it can only do so when
>>>> the connection to the GuC is awake.
>>>>
>>>> Cc: stable@vger.kernel.org
>>>> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
>>>
>>> Patch itself looks fine but I don't think we closed on the issue of
>>> stable/fixes on this patch?
>>
>> No, because TLB cache invalidation takes time and causes time outs, which
>> in turn affects applications and produce Kernel warnings.
> 
> It's not only the TLB flushes that cause grief.
> 
> There is a loop that forces a write-back of all the frame buffer pages.
> With a large display and some cpu (like my Ivy bridge one) that
> takes long enough with pre-emption disabled that wakeup of RT processes
> (and any pinned to the cpu) takes far longer than one might have
> wished for.
> 
> Since some X servers request a flush every few seconds this makes
> the system unusable for some workloads.

Ok TLB invalidations as discussed in this patch does not apply to 
Ivybridge. But what is the write back loop you mention which is causing 
you grief? What size frame buffers are we talking about here? If they 
don't fit in the mappable area recently we merged a patch* which 
improves things in that situation but not sure you are hitting exactly that.

Regards,

Tvrtko

*) 230523ba24bd ("drm/i915/gem: Don't evict unmappable VMAs when pinning 
with PIN_MAPPABLE (v2)")

RE: [Intel-gfx] [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[David Laight]

From: Tvrtko Ursulin
> Sent: 19 July 2022 08:25
...
> > It's not only the TLB flushes that cause grief.
> >
> > There is a loop that forces a write-back of all the frame buffer pages.
> > With a large display and some cpu (like my Ivy bridge one) that
> > takes long enough with pre-emption disabled that wakeup of RT processes
> > (and any pinned to the cpu) takes far longer than one might have
> > wished for.
> >
> > Since some X servers request a flush every few seconds this makes
> > the system unusable for some workloads.
> 
> Ok TLB invalidations as discussed in this patch does not apply to
> Ivybridge. But what is the write back loop you mention which is causing
> you grief? What size frame buffers are we talking about here? If they
> don't fit in the mappable area recently we merged a patch* which
> improves things in that situation but not sure you are hitting exactly that.

I found the old email:

What I've found is that the Intel i915 graphics driver uses the 'events_unbound'
kernel worker thread to periodically execute drm_cflush_sg().
(see https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/drm_cache.c)

I'm guessing this is to ensure that any writes to graphics memory become
visible is a semi-timely manner.

This loop takes about 1us per iteration split fairly evenly between whatever is in
for_each_sg_page() and drm_cflush_page().
With a 2560x1440 display the loop count is 3600 (4 bytes/pixel) and the whole
function takes around 3.3ms.

IIRC the first few page flushes are quick (I bet they go into a fifo)
and then they all get slow.
The flushes are actually requested from userspace.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Mauro Carvalho Chehab]

On Mon, 18 Jul 2022 14:52:05 +0100
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:

> 
> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> > From: Chris Wilson <chris.p.wilson@intel.com>
> > 
> > Invalidate TLB in patch, in order to reduce performance regressions.
> 
> "in batches"?

Yeah. Will fix it.

> > diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> > index d8b94d638559..2da6c82a8bd2 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> > @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
> >   void ppgtt_unbind_vma(struct i915_address_space *vm,
> >   		      struct i915_vma_resource *vma_res)
> >   {
> > -	if (vma_res->allocated)
> > -		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> > +	if (!vma_res->allocated)
> > +		return;
> > +
> > +	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> > +	if (vma_res->tlb)
> > +		vma_invalidate_tlb(vm, *vma_res->tlb);
> 
> The patch is about more than batching? If there is a security hole in 
> this area (unbind) with the current code?

No, I don't think there's a security hole. The rationale for this is
not due to it.

Since commit 2f6b90da9192 ("drm/i915: Use vma resources for async unbinding"),
VMA unbind can happen either sync or async.

So, the logic needs to do TLB invalidate on two places. After this
patch, the code at __i915_vma_evict is:

	struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
	{
...
		if (async)
			unbind_fence = i915_vma_resource_unbind(vma_res,
								&vma->obj->mm.tlb);
		else
			unbind_fence = i915_vma_resource_unbind(vma_res, NULL);

		vma->resource = NULL;

		atomic_and(~(I915_VMA_BIND_MASK | I915_VMA_ERROR | I915_VMA_GGTT_WRITE),
			   &vma->flags);

		i915_vma_detach(vma);

		if (!async) {
			if (unbind_fence) {
				dma_fence_wait(unbind_fence, false);
				dma_fence_put(unbind_fence);
				unbind_fence = NULL;
			}
			vma_invalidate_tlb(vma->vm, vma->obj->mm.tlb);
		}
...

So, basically, if !async, __i915_vma_evict() will do TLB cache invalidation.

However, when async is used, the actual page release will happen later,
at this function:

	void ppgtt_unbind_vma(struct i915_address_space *vm,
			      struct i915_vma_resource *vma_res)
	{
		if (!vma_res->allocated)
			return;

		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
		if (vma_res->tlb)
			vma_invalidate_tlb(vm, *vma_res->tlb);
	}
	
Regards,
Mauro

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Tvrtko Ursulin]

On 20/07/2022 08:13, Mauro Carvalho Chehab wrote:
> On Mon, 18 Jul 2022 14:52:05 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
>>
>> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
>>> From: Chris Wilson <chris.p.wilson@intel.com>
>>>
>>> Invalidate TLB in patch, in order to reduce performance regressions.
>>
>> "in batches"?
> 
> Yeah. Will fix it.
> 
>>> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
>>> index d8b94d638559..2da6c82a8bd2 100644
>>> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
>>> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
>>> @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
>>>    void ppgtt_unbind_vma(struct i915_address_space *vm,
>>>    		      struct i915_vma_resource *vma_res)
>>>    {
>>> -	if (vma_res->allocated)
>>> -		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
>>> +	if (!vma_res->allocated)
>>> +		return;
>>> +
>>> +	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
>>> +	if (vma_res->tlb)
>>> +		vma_invalidate_tlb(vm, *vma_res->tlb);
>>
>> The patch is about more than batching? If there is a security hole in
>> this area (unbind) with the current code?
> 
> No, I don't think there's a security hole. The rationale for this is
> not due to it.

In this case obvious question is why are these changes in the patch 
which declares itself to be about batching invalidations? Because...

> Since commit 2f6b90da9192 ("drm/i915: Use vma resources for async unbinding"),
> VMA unbind can happen either sync or async.
> 
> So, the logic needs to do TLB invalidate on two places. After this
> patch, the code at __i915_vma_evict is:
> 
> 	struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
> 	{
> ...
> 		if (async)
> 			unbind_fence = i915_vma_resource_unbind(vma_res,
> 								&vma->obj->mm.tlb);
> 		else
> 			unbind_fence = i915_vma_resource_unbind(vma_res, NULL);
> 
> 		vma->resource = NULL;
> 
> 		atomic_and(~(I915_VMA_BIND_MASK | I915_VMA_ERROR | I915_VMA_GGTT_WRITE),
> 			   &vma->flags);
> 
> 		i915_vma_detach(vma);
> 
> 		if (!async) {
> 			if (unbind_fence) {
> 				dma_fence_wait(unbind_fence, false);
> 				dma_fence_put(unbind_fence);
> 				unbind_fence = NULL;
> 			}
> 			vma_invalidate_tlb(vma->vm, vma->obj->mm.tlb);
> 		}
> ...
> 
> So, basically, if !async, __i915_vma_evict() will do TLB cache invalidation.
> 
> However, when async is used, the actual page release will happen later,
> at this function:
> 
> 	void ppgtt_unbind_vma(struct i915_address_space *vm,
> 			      struct i915_vma_resource *vma_res)
> 	{
> 		if (!vma_res->allocated)
> 			return;
> 
> 		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> 		if (vma_res->tlb)
> 			vma_invalidate_tlb(vm, *vma_res->tlb);
> 	}

.. frankly I don't follow since I don't see any page release happening 
in here. Just PTE clearing.

I am explaining why it looks to me that the patch is doing two things. 
Implementing batching _and_ adding invalidation points at VMA unbind 
sites, while so far we had it at backing store release only. Maybe I am 
wrong and perhaps I am too slow to pick up on the explanation here.

So if the patch is doing two things please split it up.

I am further confused by the invalidation call site in evict and in 
unbind - why there can't be one logical site since the logical sequence 
is evict -> unbind.

Regards,

Tvrtko

Re: [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Tvrtko Ursulin]

On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Invalidate TLB in patch, in order to reduce performance regressions.
> 
> Currently, every caller performs a full barrier around a TLB
> invalidation, ignoring all other invalidations that may have already
> removed their PTEs from the cache. As this is a synchronous operation
> and can be quite slow, we cause multiple threads to contend on the TLB
> invalidate mutex blocking userspace.
> 
> We only need to invalidate the TLB once after replacing our PTE to
> ensure that there is no possible continued access to the physical
> address before releasing our pages. By tracking a seqno for each full
> TLB invalidate we can quickly determine if one has been performed since
> rewriting the PTE, and only if necessary trigger one for ourselves.
> 
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
> 
> [mchehab: rebased to not require moving the code to a separate file]
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>   .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 +-
>   drivers/gpu/drm/i915/gem/i915_gem_pages.c     | 21 +++++---
>   drivers/gpu/drm/i915/gt/intel_gt.c            | 53 ++++++++++++++-----
>   drivers/gpu/drm/i915/gt/intel_gt.h            | 12 ++++-
>   drivers/gpu/drm/i915/gt/intel_gt_types.h      | 18 ++++++-
>   drivers/gpu/drm/i915/gt/intel_ppgtt.c         |  8 ++-
>   drivers/gpu/drm/i915/i915_vma.c               | 34 +++++++++---
>   drivers/gpu/drm/i915/i915_vma.h               |  1 +
>   drivers/gpu/drm/i915/i915_vma_resource.c      |  5 +-
>   drivers/gpu/drm/i915/i915_vma_resource.h      |  6 ++-
>   10 files changed, 125 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> index 5cf36a130061..9f6b14ec189a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -335,7 +335,6 @@ struct drm_i915_gem_object {
>   #define I915_BO_READONLY          BIT(7)
>   #define I915_TILING_QUIRK_BIT     8 /* unknown swizzling; do not release! */
>   #define I915_BO_PROTECTED         BIT(9)
> -#define I915_BO_WAS_BOUND_BIT     10
>   	/**
>   	 * @mem_flags - Mutable placement-related flags
>   	 *
> @@ -616,6 +615,8 @@ struct drm_i915_gem_object {
>   		 * pages were last acquired.
>   		 */
>   		bool dirty:1;
> +
> +		u32 tlb;
>   	} mm;
>   
>   	struct {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 6835279943df..8357dbdcab5c 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -191,6 +191,18 @@ static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
>   		vunmap(ptr);
>   }
>   
> +static void flush_tlb_invalidate(struct drm_i915_gem_object *obj)
> +{
> +	struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +	struct intel_gt *gt = to_gt(i915);
> +
> +	if (!obj->mm.tlb)
> +		return;
> +
> +	intel_gt_invalidate_tlb(gt, obj->mm.tlb);
> +	obj->mm.tlb = 0;
> +}
> +
>   struct sg_table *
>   __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>   {
> @@ -216,14 +228,7 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>   	__i915_gem_object_reset_page_iter(obj);
>   	obj->mm.page_sizes.phys = obj->mm.page_sizes.sg = 0;
>   
> -	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
> -		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> -		struct intel_gt *gt = to_gt(i915);
> -		intel_wakeref_t wakeref;
> -
> -		with_intel_gt_pm_if_awake(gt, wakeref)
> -			intel_gt_invalidate_tlbs(gt);
> -	}
> +	flush_tlb_invalidate(obj);
>   
>   	return pages;
>   }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 5c55a90672f4..f435e06125aa 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -38,8 +38,6 @@ static void __intel_gt_init_early(struct intel_gt *gt)
>   {
>   	spin_lock_init(&gt->irq_lock);
>   
> -	mutex_init(&gt->tlb_invalidate_lock);
> -
>   	INIT_LIST_HEAD(&gt->closed_vma);
>   	spin_lock_init(&gt->closed_lock);
>   
> @@ -50,6 +48,8 @@ static void __intel_gt_init_early(struct intel_gt *gt)
>   	intel_gt_init_reset(gt);
>   	intel_gt_init_requests(gt);
>   	intel_gt_init_timelines(gt);
> +	mutex_init(&gt->tlb.invalidate_lock);
> +	seqcount_mutex_init(&gt->tlb.seqno, &gt->tlb.invalidate_lock);
>   	intel_gt_pm_init_early(gt);
>   
>   	intel_uc_init_early(&gt->uc);
> @@ -770,6 +770,7 @@ void intel_gt_driver_late_release_all(struct drm_i915_private *i915)
>   		intel_gt_fini_requests(gt);
>   		intel_gt_fini_reset(gt);
>   		intel_gt_fini_timelines(gt);
> +		mutex_destroy(&gt->tlb.invalidate_lock);
>   		intel_engines_free(gt);
>   	}
>   }
> @@ -908,7 +909,7 @@ get_reg_and_bit(const struct intel_engine_cs *engine, const bool gen8,
>   	return rb;
>   }
>   
> -void intel_gt_invalidate_tlbs(struct intel_gt *gt)
> +static void mmio_invalidate_full(struct intel_gt *gt)
>   {
>   	static const i915_reg_t gen8_regs[] = {
>   		[RENDER_CLASS]			= GEN8_RTCR,
> @@ -931,12 +932,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	const i915_reg_t *regs;
>   	unsigned int num = 0;
>   
> -	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
> -		return;
> -
> -	if (intel_gt_is_wedged(gt))
> -		return;
> -
>   	if (GRAPHICS_VER(i915) == 12) {
>   		regs = gen12_regs;
>   		num = ARRAY_SIZE(gen12_regs);
> @@ -951,9 +946,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   			  "Platform does not implement TLB invalidation!"))
>   		return;
>   
> -	GEM_TRACE("\n");
> -
> -	mutex_lock(&gt->tlb_invalidate_lock);
>   	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>   
>   	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
> @@ -973,6 +965,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   		awake |= engine->mask;
>   	}
>   
> +	GT_TRACE(gt, "invalidated engines %08x\n", awake);
> +
>   	/* Wa_2207587034:tgl,dg1,rkl,adl-s,adl-p */
>   	if (awake &&
>   	    (IS_TIGERLAKE(i915) ||
> @@ -1012,5 +1006,38 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	 * transitions.
>   	 */
>   	intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL);
> -	mutex_unlock(&gt->tlb_invalidate_lock);
> +}
> +
> +static bool tlb_seqno_passed(const struct intel_gt *gt, u32 seqno)
> +{
> +	u32 cur = intel_gt_tlb_seqno(gt);
> +
> +	/* Only skip if a *full* TLB invalidate barrier has passed */
> +	return (s32)(cur - ALIGN(seqno, 2)) > 0;
> +}
> +
> +void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
> +{
> +	intel_wakeref_t wakeref;
> +
> +	if (I915_SELFTEST_ONLY(gt->awake == -ENODEV))
> +		return;
> +
> +	if (intel_gt_is_wedged(gt))
> +		return;
> +
> +	if (tlb_seqno_passed(gt, seqno))
> +		return;
> +
> +	with_intel_gt_pm_if_awake(gt, wakeref) {
> +		mutex_lock(&gt->tlb.invalidate_lock);
> +		if (tlb_seqno_passed(gt, seqno))
> +			goto unlock;
> +
> +		mmio_invalidate_full(gt);
> +
> +		write_seqcount_invalidate(&gt->tlb.seqno);
> +unlock:
> +		mutex_unlock(&gt->tlb.invalidate_lock);
> +	}
>   }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
> index 82d6f248d876..40b06adf509a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.h
> @@ -101,6 +101,16 @@ void intel_gt_info_print(const struct intel_gt_info *info,
>   
>   void intel_gt_watchdog_work(struct work_struct *work);
>   
> -void intel_gt_invalidate_tlbs(struct intel_gt *gt);
> +static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt)
> +{
> +	return seqprop_sequence(&gt->tlb.seqno);
> +}
> +
> +static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt)
> +{
> +	return intel_gt_tlb_seqno(gt) | 1;
> +}
> +
> +void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno);
>   
>   #endif /* __INTEL_GT_H__ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> index df708802889d..3804a583382b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
> @@ -11,6 +11,7 @@
>   #include <linux/llist.h>
>   #include <linux/mutex.h>
>   #include <linux/notifier.h>
> +#include <linux/seqlock.h>
>   #include <linux/spinlock.h>
>   #include <linux/types.h>
>   #include <linux/workqueue.h>
> @@ -83,7 +84,22 @@ struct intel_gt {
>   	struct intel_uc uc;
>   	struct intel_gsc gsc;
>   
> -	struct mutex tlb_invalidate_lock;
> +	struct {
> +		/* Serialize global tlb invalidations */
> +		struct mutex invalidate_lock;
> +
> +		/*
> +		 * Batch TLB invalidations
> +		 *
> +		 * After unbinding the PTE, we need to ensure the TLB
> +		 * are invalidated prior to releasing the physical pages.
> +		 * But we only need one such invalidation for all unbinds,
> +		 * so we track how many TLB invalidations have been
> +		 * performed since unbind the PTE and only emit an extra
> +		 * invalidate if no full barrier has been passed.
> +		 */
> +		seqcount_mutex_t seqno;
> +	} tlb;
>   
>   	struct i915_wa_list wa_list;
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> index d8b94d638559..2da6c82a8bd2 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
>   void ppgtt_unbind_vma(struct i915_address_space *vm,
>   		      struct i915_vma_resource *vma_res)
>   {
> -	if (vma_res->allocated)
> -		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> +	if (!vma_res->allocated)
> +		return;
> +
> +	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> +	if (vma_res->tlb)
> +		vma_invalidate_tlb(vm, *vma_res->tlb);
>   }
>   
>   static unsigned long pd_count(u64 size, int shift)
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 646f419b2035..84a9ccbc5fc5 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -538,9 +538,6 @@ int i915_vma_bind(struct i915_vma *vma,
>   				   bind_flags);
>   	}
>   
> -	if (bind_flags & I915_VMA_LOCAL_BIND)
> -		set_bit(I915_BO_WAS_BOUND_BIT, &vma->obj->flags);
> -
>   	atomic_or(bind_flags, &vma->flags);
>   	return 0;
>   }
> @@ -1311,6 +1308,19 @@ I915_SELFTEST_EXPORT int i915_vma_get_pages(struct i915_vma *vma)
>   	return err;
>   }
>   
> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb)
> +{
> +	/*
> +	 * Before we release the pages that were bound by this vma, we
> +	 * must invalidate all the TLBs that may still have a reference
> +	 * back to our physical address. It only needs to be done once,
> +	 * so after updating the PTE to point away from the pages, record
> +	 * the most recent TLB invalidation seqno, and if we have not yet
> +	 * flushed the TLBs upon release, perform a full invalidation.
> +	 */
> +	WRITE_ONCE(tlb, intel_gt_next_invalidate_tlb_full(vm->gt));

Shouldn't tlb be a pointer for this to make sense?

Regards,

Tvrtko

> +}
> +
>   static void __vma_put_pages(struct i915_vma *vma, unsigned int count)
>   {
>   	/* We allocate under vma_get_pages, so beware the shrinker */
> @@ -1942,7 +1952,12 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
>   		vma->vm->skip_pte_rewrite;
>   	trace_i915_vma_unbind(vma);
>   
> -	unbind_fence = i915_vma_resource_unbind(vma_res);
> +	if (async)
> +		unbind_fence = i915_vma_resource_unbind(vma_res,
> +							&vma->obj->mm.tlb);
> +	else
> +		unbind_fence = i915_vma_resource_unbind(vma_res, NULL);
> +
>   	vma->resource = NULL;
>   
>   	atomic_and(~(I915_VMA_BIND_MASK | I915_VMA_ERROR | I915_VMA_GGTT_WRITE),
> @@ -1950,10 +1965,13 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
>   
>   	i915_vma_detach(vma);
>   
> -	if (!async && unbind_fence) {
> -		dma_fence_wait(unbind_fence, false);
> -		dma_fence_put(unbind_fence);
> -		unbind_fence = NULL;
> +	if (!async) {
> +		if (unbind_fence) {
> +			dma_fence_wait(unbind_fence, false);
> +			dma_fence_put(unbind_fence);
> +			unbind_fence = NULL;
> +		}
> +		vma_invalidate_tlb(vma->vm, vma->obj->mm.tlb);
>   	}
>   
>   	/*
> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
> index 88ca0bd9c900..5048eed536da 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -213,6 +213,7 @@ bool i915_vma_misplaced(const struct i915_vma *vma,
>   			u64 size, u64 alignment, u64 flags);
>   void __i915_vma_set_map_and_fenceable(struct i915_vma *vma);
>   void i915_vma_revoke_mmap(struct i915_vma *vma);
> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb);
>   struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async);
>   int __i915_vma_unbind(struct i915_vma *vma);
>   int __must_check i915_vma_unbind(struct i915_vma *vma);
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.c b/drivers/gpu/drm/i915/i915_vma_resource.c
> index 27c55027387a..5a67995ea5fe 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.c
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.c
> @@ -223,10 +223,13 @@ i915_vma_resource_fence_notify(struct i915_sw_fence *fence,
>    * Return: A refcounted pointer to a dma-fence that signals when unbinding is
>    * complete.
>    */
> -struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res)
> +struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
> +					   u32 *tlb)
>   {
>   	struct i915_address_space *vm = vma_res->vm;
>   
> +	vma_res->tlb = tlb;
> +
>   	/* Reference for the sw fence */
>   	i915_vma_resource_get(vma_res);
>   
> diff --git a/drivers/gpu/drm/i915/i915_vma_resource.h b/drivers/gpu/drm/i915/i915_vma_resource.h
> index 5d8427caa2ba..06923d1816e7 100644
> --- a/drivers/gpu/drm/i915/i915_vma_resource.h
> +++ b/drivers/gpu/drm/i915/i915_vma_resource.h
> @@ -67,6 +67,7 @@ struct i915_page_sizes {
>    * taken when the unbind is scheduled.
>    * @skip_pte_rewrite: During ggtt suspend and vm takedown pte rewriting
>    * needs to be skipped for unbind.
> + * @tlb: pointer for obj->mm.tlb, if async unbind. Otherwise, NULL
>    *
>    * The lifetime of a struct i915_vma_resource is from a binding request to
>    * the actual possible asynchronous unbind has completed.
> @@ -119,6 +120,8 @@ struct i915_vma_resource {
>   	bool immediate_unbind:1;
>   	bool needs_wakeref:1;
>   	bool skip_pte_rewrite:1;
> +
> +	u32 *tlb;
>   };
>   
>   bool i915_vma_resource_hold(struct i915_vma_resource *vma_res,
> @@ -131,7 +134,8 @@ struct i915_vma_resource *i915_vma_resource_alloc(void);
>   
>   void i915_vma_resource_free(struct i915_vma_resource *vma_res);
>   
> -struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res);
> +struct dma_fence *i915_vma_resource_unbind(struct i915_vma_resource *vma_res,
> +					   u32 *tlb);
>   
>   void __i915_vma_resource_init(struct i915_vma_resource *vma_res);
>   

Re: [PATCH v2 01/21] drm/i915/gt: Ignore TLB invalidations on idle engines

[Andi Shyti]

Hi Mauro,

On Thu, Jul 14, 2022 at 01:06:06PM +0100, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Check if the device is powered down prior to any engine activity,
> as, on such cases, all the TLBs were already invalidated, so an
> explicit TLB invalidation is not needed, thus reducing the
> performance regression impact due to it.
> 
> This becomes more significant with GuC, as it can only do so when
> the connection to the GuC is awake.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

For me it's good, but please, sort out with Tvrtko about his
doubts:

Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>

Andi

> ---
> 
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v2 00/21] at: https://lore.kernel.org/all/cover.1657800199.git.mchehab@kernel.org/
> 
>  drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 ++++++----
>  drivers/gpu/drm/i915/gt/intel_gt.c        | 17 ++++++++++-------
>  drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 +++
>  3 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 97c820eee115..6835279943df 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -6,14 +6,15 @@
>  
>  #include <drm/drm_cache.h>
>  
> +#include "gt/intel_gt.h"
> +#include "gt/intel_gt_pm.h"
> +
>  #include "i915_drv.h"
>  #include "i915_gem_object.h"
>  #include "i915_scatterlist.h"
>  #include "i915_gem_lmem.h"
>  #include "i915_gem_mman.h"
>  
> -#include "gt/intel_gt.h"
> -
>  void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
>  				 struct sg_table *pages,
>  				 unsigned int sg_page_sizes)
> @@ -217,10 +218,11 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
>  
>  	if (test_and_clear_bit(I915_BO_WAS_BOUND_BIT, &obj->flags)) {
>  		struct drm_i915_private *i915 = to_i915(obj->base.dev);
> +		struct intel_gt *gt = to_gt(i915);
>  		intel_wakeref_t wakeref;
>  
> -		with_intel_runtime_pm_if_active(&i915->runtime_pm, wakeref)
> -			intel_gt_invalidate_tlbs(to_gt(i915));
> +		with_intel_gt_pm_if_awake(gt, wakeref)
> +			intel_gt_invalidate_tlbs(gt);
>  	}
>  
>  	return pages;
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 68c2b0d8f187..c4d43da84d8e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -12,6 +12,7 @@
>  
>  #include "i915_drv.h"
>  #include "intel_context.h"
> +#include "intel_engine_pm.h"
>  #include "intel_engine_regs.h"
>  #include "intel_ggtt_gmch.h"
>  #include "intel_gt.h"
> @@ -924,6 +925,7 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>  	struct drm_i915_private *i915 = gt->i915;
>  	struct intel_uncore *uncore = gt->uncore;
>  	struct intel_engine_cs *engine;
> +	intel_engine_mask_t awake, tmp;
>  	enum intel_engine_id id;
>  	const i915_reg_t *regs;
>  	unsigned int num = 0;
> @@ -947,26 +949,31 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>  
>  	GEM_TRACE("\n");
>  
> -	assert_rpm_wakelock_held(&i915->runtime_pm);
> -
>  	mutex_lock(&gt->tlb_invalidate_lock);
>  	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>  
>  	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
>  
> +	awake = 0;
>  	for_each_engine(engine, gt, id) {
>  		struct reg_and_bit rb;
>  
> +		if (!intel_engine_pm_is_awake(engine))
> +			continue;
> +
>  		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
>  		if (!i915_mmio_reg_offset(rb.reg))
>  			continue;
>  
>  		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
> +		awake |= engine->mask;
>  	}
>  
>  	spin_unlock_irq(&uncore->lock);
>  
> -	for_each_engine(engine, gt, id) {
> +	for_each_engine_masked(engine, gt, awake, tmp) {
> +		struct reg_and_bit rb;
> +
>  		/*
>  		 * HW architecture suggest typical invalidation time at 40us,
>  		 * with pessimistic cases up to 100us and a recommendation to
> @@ -974,12 +981,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>  		 */
>  		const unsigned int timeout_us = 100;
>  		const unsigned int timeout_ms = 4;
> -		struct reg_and_bit rb;
>  
>  		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> -		if (!i915_mmio_reg_offset(rb.reg))
> -			continue;
> -
>  		if (__intel_wait_for_register_fw(uncore,
>  						 rb.reg, rb.bit, 0,
>  						 timeout_us, timeout_ms,
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> index bc898df7a48c..a334787a4939 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> @@ -55,6 +55,9 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
>  	for (tmp = 1, intel_gt_pm_get(gt); tmp; \
>  	     intel_gt_pm_put(gt), tmp = 0)
>  
> +#define with_intel_gt_pm_if_awake(gt, wf) \
> +	for (wf = intel_gt_pm_get_if_awake(gt); wf; intel_gt_pm_put_async(gt), wf = 0)
> +
>  static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
>  {
>  	return intel_wakeref_wait_for_idle(&gt->wakeref);
> -- 
> 2.36.1

Re: [PATCH v2 03/21] drm/i915/gt: Invalidate TLB of the OA unit at TLB invalidations

[Andi Shyti]

Hi Mauro and Chris,

On Thu, Jul 14, 2022 at 01:06:08PM +0100, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Ensure that the TLB of the OA unit is also invalidated
> on gen12 HW, as just invalidating the TLB of an engine is not
> enough.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>

Thanks,
Andi

Re: [PATCH v2 04/21] drm/i915/gt: Only invalidate TLBs exposed to user manipulation

[Andi Shyti]

Hi Mauro,

On Thu, Jul 14, 2022 at 01:06:09PM +0100, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Don't flush TLBs when the buffer is only used in the GGTT under full
> control of the kernel, as there's no risk of concurrent access
> and stale access from prefetch.
> 
> We only need to invalidate the TLB if they are accessible by the user.
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Please, once you have sorted out Tvrtko's question you can add:

Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>

Thanks,
Andi

Re: [PATCH v2 05/21] drm/i915/gt: Skip TLB invalidations once wedged

[Andi Shyti]

Hi Mauro,

On Thu, Jul 14, 2022 at 01:06:10PM +0100, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
> 
> Skip all further TLB invalidations once the device is wedged and
> had been reset, as, on such cases, it can no longer process instructions
> on the GPU and the user no longer has access to the TLB's in each engine.
> 
> That helps to reduce the performance regression introduced by TLB
> invalidate logic.
> 
> Cc: stable@vger.kernel.org
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> Cc: Fei Yang <fei.yang@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

I haven't read any concern from Tvrtko here, in any case:

Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>

thanks,
Andi

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Mauro Carvalho Chehab]

On Wed, 20 Jul 2022 11:49:59 +0100
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:

> On 20/07/2022 08:13, Mauro Carvalho Chehab wrote:
> > On Mon, 18 Jul 2022 14:52:05 +0100
> > Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> >   
> >>
> >> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:  
> >>> From: Chris Wilson <chris.p.wilson@intel.com>
> >>>
> >>> Invalidate TLB in patch, in order to reduce performance regressions.  
> >>
> >> "in batches"?  
> > 
> > Yeah. Will fix it.

> > +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb)
> > +{
> > +	/*
> > +	 * Before we release the pages that were bound by this vma, we
> > +	 * must invalidate all the TLBs that may still have a reference
> > +	 * back to our physical address. It only needs to be done once,
> > +	 * so after updating the PTE to point away from the pages, record
> > +	 * the most recent TLB invalidation seqno, and if we have not yet
> > +	 * flushed the TLBs upon release, perform a full invalidation.
> > +	 */
> > +	WRITE_ONCE(tlb, intel_gt_next_invalidate_tlb_full(vm->gt));  
> 
> Shouldn't tlb be a pointer for this to make sense?

Oh, my mistake! Will fix at the next version.

> >   
> >>> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> >>> index d8b94d638559..2da6c82a8bd2 100644
> >>> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> >>> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> >>> @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
> >>>    void ppgtt_unbind_vma(struct i915_address_space *vm,
> >>>    		      struct i915_vma_resource *vma_res)
> >>>    {
> >>> -	if (vma_res->allocated)
> >>> -		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> >>> +	if (!vma_res->allocated)
> >>> +		return;
> >>> +
> >>> +	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
> >>> +	if (vma_res->tlb)
> >>> +		vma_invalidate_tlb(vm, *vma_res->tlb);  
> >>
> >> The patch is about more than batching? If there is a security hole in
> >> this area (unbind) with the current code?  
> > 
> > No, I don't think there's a security hole. The rationale for this is
> > not due to it.  
> 
> In this case obvious question is why are these changes in the patch 
> which declares itself to be about batching invalidations? Because...

Because vma_invalidate_tlb() basically stores a TLB seqno, but the
actual invalidation is deferred to when the pages are unset, at
__i915_gem_object_unset_pages().

So, what happens is:

- on VMA sync mode, the need to invalidate TLB is marked at
  __vma_put_pages(), before VMA unbind;
- on async, this is deferred to happen at ppgtt_unbind_vma(), where
  it marks the need to invalidate TLBs.

On both cases, __i915_gem_object_unset_pages() is called later,
when the driver is ready to unmap the page.

> I am explaining why it looks to me that the patch is doing two things. 
> Implementing batching _and_ adding invalidation points at VMA unbind 
> sites, while so far we had it at backing store release only. Maybe I am 
> wrong and perhaps I am too slow to pick up on the explanation here.
> 
> So if the patch is doing two things please split it up.
> 
> I am further confused by the invalidation call site in evict and in 
> unbind - why there can't be one logical site since the logical sequence 
> is evict -> unbind.

The invalidation happens only on one place: __i915_gem_object_unset_pages().

Despite its name, vma_invalidate_tlb() just marks the need of doing TLB
invalidation.

Regards,
Mauro

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Tvrtko Ursulin]

On 27/07/2022 12:48, Mauro Carvalho Chehab wrote:
> On Wed, 20 Jul 2022 11:49:59 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
>> On 20/07/2022 08:13, Mauro Carvalho Chehab wrote:
>>> On Mon, 18 Jul 2022 14:52:05 +0100
>>> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
>>>    
>>>>
>>>> On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
>>>>> From: Chris Wilson <chris.p.wilson@intel.com>
>>>>>
>>>>> Invalidate TLB in patch, in order to reduce performance regressions.
>>>>
>>>> "in batches"?
>>>
>>> Yeah. Will fix it.
> 
>>> +void vma_invalidate_tlb(struct i915_address_space *vm, u32 tlb)
>>> +{
>>> +	/*
>>> +	 * Before we release the pages that were bound by this vma, we
>>> +	 * must invalidate all the TLBs that may still have a reference
>>> +	 * back to our physical address. It only needs to be done once,
>>> +	 * so after updating the PTE to point away from the pages, record
>>> +	 * the most recent TLB invalidation seqno, and if we have not yet
>>> +	 * flushed the TLBs upon release, perform a full invalidation.
>>> +	 */
>>> +	WRITE_ONCE(tlb, intel_gt_next_invalidate_tlb_full(vm->gt));
>>
>> Shouldn't tlb be a pointer for this to make sense?
> 
> Oh, my mistake! Will fix at the next version.
> 
>>>    
>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
>>>>> index d8b94d638559..2da6c82a8bd2 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
>>>>> @@ -206,8 +206,12 @@ void ppgtt_bind_vma(struct i915_address_space *vm,
>>>>>     void ppgtt_unbind_vma(struct i915_address_space *vm,
>>>>>     		      struct i915_vma_resource *vma_res)
>>>>>     {
>>>>> -	if (vma_res->allocated)
>>>>> -		vm->clear_range(vm, vma_res->start, vma_res->vma_size);
>>>>> +	if (!vma_res->allocated)
>>>>> +		return;
>>>>> +
>>>>> +	vm->clear_range(vm, vma_res->start, vma_res->vma_size);
>>>>> +	if (vma_res->tlb)
>>>>> +		vma_invalidate_tlb(vm, *vma_res->tlb);
>>>>
>>>> The patch is about more than batching? If there is a security hole in
>>>> this area (unbind) with the current code?
>>>
>>> No, I don't think there's a security hole. The rationale for this is
>>> not due to it.
>>
>> In this case obvious question is why are these changes in the patch
>> which declares itself to be about batching invalidations? Because...
> 
> Because vma_invalidate_tlb() basically stores a TLB seqno, but the
> actual invalidation is deferred to when the pages are unset, at
> __i915_gem_object_unset_pages().
> 
> So, what happens is:
> 
> - on VMA sync mode, the need to invalidate TLB is marked at
>    __vma_put_pages(), before VMA unbind;
> - on async, this is deferred to happen at ppgtt_unbind_vma(), where
>    it marks the need to invalidate TLBs.
> 
> On both cases, __i915_gem_object_unset_pages() is called later,
> when the driver is ready to unmap the page.

Sorry still not clear to me why is the patch moving marking of the need 
to invalidate (regardless if it a bit like today, or a seqno like in 
this patch) from bind to unbind?

What if the seqno was stored in i915_vma_bind, where the bit is set 
today, and all the hunks which touch the unbind and evict would 
disappear from the patch. What wouldn't work in that case, if anything?

Regards,

Tvrtko

> 
>> I am explaining why it looks to me that the patch is doing two things.
>> Implementing batching _and_ adding invalidation points at VMA unbind
>> sites, while so far we had it at backing store release only. Maybe I am
>> wrong and perhaps I am too slow to pick up on the explanation here.
>>
>> So if the patch is doing two things please split it up.
>>
>> I am further confused by the invalidation call site in evict and in
>> unbind - why there can't be one logical site since the logical sequence
>> is evict -> unbind.
> 
> The invalidation happens only on one place: __i915_gem_object_unset_pages().
> 
> Despite its name, vma_invalidate_tlb() just marks the need of doing TLB
> invalidation.
> 
> Regards,
> Mauro

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Mauro Carvalho Chehab]

On Wed, 27 Jul 2022 13:56:50 +0100
Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:

> > Because vma_invalidate_tlb() basically stores a TLB seqno, but the
> > actual invalidation is deferred to when the pages are unset, at
> > __i915_gem_object_unset_pages().
> > 
> > So, what happens is:
> > 
> > - on VMA sync mode, the need to invalidate TLB is marked at
> >    __vma_put_pages(), before VMA unbind;
> > - on async, this is deferred to happen at ppgtt_unbind_vma(), where
> >    it marks the need to invalidate TLBs.
> > 
> > On both cases, __i915_gem_object_unset_pages() is called later,
> > when the driver is ready to unmap the page.  
> 
> Sorry still not clear to me why is the patch moving marking of the need 
> to invalidate (regardless if it a bit like today, or a seqno like in 
> this patch) from bind to unbind?
> 
> What if the seqno was stored in i915_vma_bind, where the bit is set 
> today, and all the hunks which touch the unbind and evict would 
> disappear from the patch. What wouldn't work in that case, if anything?

Ah, now I see your point.

I can't see any sense on having a sequence number at VMA bind, as the
unbind order can be different. The need of doing a full TLB invalidation
or not depends on the unbind order.

The way the current algorithm works is that drm_i915_gem_object can be
created on any order, and, at unbind/evict, they receive a seqno.

The seqno is incremented at intel_gt_invalidate_tlb():

    void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
    {
	with_intel_gt_pm_if_awake(gt, wakeref) {
		mutex_lock(&gt->tlb.invalidate_lock);
		if (tlb_seqno_passed(gt, seqno))
				goto unlock;

		mmio_invalidate_full(gt);

		write_seqcount_invalidate(&gt->tlb.seqno);	// increment seqno
		

So, let's say 3 objects were created, on this order:

	obj1
	obj2
	obj3

They would be unbind/evict on a different order. On that time, 
the mm.tlb will be stamped with a seqno, using the number from the
last TLB flush, plus 1.

As different threads can be used to handle TLB flushes, let's imagine
two threads (just for the sake of having an example). On such case,
what we would have is:

seqno		Thread 0			Thread 1

seqno=2		unbind/evict event
		obj3.mm.tlb = seqno | 1
seqno=2		unbind/evict event
		obj1.mm.tlb = seqno | 1
						__i915_gem_object_unset_pages() 
						called for obj3, TLB flush happened,
						invalidating both obj1 and obj2.
						seqno += 2					
seqno=4		unbind/evict event
		obj1.mm.tlb = seqno | 1
						__i915_gem_object_unset_pages()
						called for obj1, don't flush.
...
						__i915_gem_object_unset_pages() called for obj2, TLB flush happened
						seqno += 2
seqno=6

So, basically the seqno is used to track when the object data stopped
being updated, because of an unbind/evict event, being later used by
intel_gt_invalidate_tlb() when called from __i915_gem_object_unset_pages(),
in order to check if a previous invalidation call was enough to invalidate
the object, or if a new call is needed.

Now, if seqno is stored at bind, data can still leak, as the assumption
made by intel_gt_invalidate_tlb() that the data stopped being used at
seqno is not true anymore.

Still, I agree that this logic is complex and should be better 
documented. So, if you're now OK with this patch, I'll add the above
explanation inside a kernel-doc comment.

Regards,
Mauro

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Mauro Carvalho Chehab]

On Thu, 28 Jul 2022 08:32:32 +0200
Mauro Carvalho Chehab <mauro.chehab@linux.intel.com> wrote:

> On Wed, 27 Jul 2022 13:56:50 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
> > > Because vma_invalidate_tlb() basically stores a TLB seqno, but the
> > > actual invalidation is deferred to when the pages are unset, at
> > > __i915_gem_object_unset_pages().
> > > 
> > > So, what happens is:
> > > 
> > > - on VMA sync mode, the need to invalidate TLB is marked at
> > >    __vma_put_pages(), before VMA unbind;
> > > - on async, this is deferred to happen at ppgtt_unbind_vma(), where
> > >    it marks the need to invalidate TLBs.
> > > 
> > > On both cases, __i915_gem_object_unset_pages() is called later,
> > > when the driver is ready to unmap the page.    
> > 
> > Sorry still not clear to me why is the patch moving marking of the need 
> > to invalidate (regardless if it a bit like today, or a seqno like in 
> > this patch) from bind to unbind?
> > 
> > What if the seqno was stored in i915_vma_bind, where the bit is set 
> > today, and all the hunks which touch the unbind and evict would 
> > disappear from the patch. What wouldn't work in that case, if anything?  
> 
> Ah, now I see your point.
> 
> I can't see any sense on having a sequence number at VMA bind, as the
> unbind order can be different. The need of doing a full TLB invalidation
> or not depends on the unbind order.
> 
> The way the current algorithm works is that drm_i915_gem_object can be
> created on any order, and, at unbind/evict, they receive a seqno.
> 
> The seqno is incremented at intel_gt_invalidate_tlb():
> 
>     void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
>     {
> 	with_intel_gt_pm_if_awake(gt, wakeref) {
> 		mutex_lock(&gt->tlb.invalidate_lock);
> 		if (tlb_seqno_passed(gt, seqno))
> 				goto unlock;
> 
> 		mmio_invalidate_full(gt);
> 
> 		write_seqcount_invalidate(&gt->tlb.seqno);	// increment seqno
> 		
> 
> So, let's say 3 objects were created, on this order:
> 
> 	obj1
> 	obj2
> 	obj3
> 
> They would be unbind/evict on a different order. On that time, 
> the mm.tlb will be stamped with a seqno, using the number from the
> last TLB flush, plus 1.
> 
> As different threads can be used to handle TLB flushes, let's imagine
> two threads (just for the sake of having an example). On such case,
> what we would have is:
> 
> seqno		Thread 0			Thread 1
> 
> seqno=2		unbind/evict event
> 		obj3.mm.tlb = seqno | 1
> seqno=2		unbind/evict event
> 		obj1.mm.tlb = seqno | 1
> 						__i915_gem_object_unset_pages() 
> 						called for obj3, TLB flush happened,
> 						invalidating both obj1 and obj2.
> 						seqno += 2					
> seqno=4		unbind/evict event
> 		obj1.mm.tlb = seqno | 1

cut-and-paste typo. it should be, instead:

 		obj2.mm.tlb = seqno | 1


> 						__i915_gem_object_unset_pages()
> 						called for obj1, don't flush.
> ...
> 						__i915_gem_object_unset_pages() called for obj2, TLB flush happened
> 						seqno += 2
> seqno=6
> 
> So, basically the seqno is used to track when the object data stopped
> being updated, because of an unbind/evict event, being later used by
> intel_gt_invalidate_tlb() when called from __i915_gem_object_unset_pages(),
> in order to check if a previous invalidation call was enough to invalidate
> the object, or if a new call is needed.
> 
> Now, if seqno is stored at bind, data can still leak, as the assumption
> made by intel_gt_invalidate_tlb() that the data stopped being used at
> seqno is not true anymore.
> 
> Still, I agree that this logic is complex and should be better 
> documented. So, if you're now OK with this patch, I'll add the above
> explanation inside a kernel-doc comment.

I'm enclosing the kernel-doc patch (to be applied after moving the code into
its own files: intel_tlb.c/intel_tlb.h):

[PATCH] drm/i915/gt: document TLB cache invalidation functions

Add a description for the TLB cache invalidation algorithm and for
the related kAPI functions.

Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.c b/drivers/gpu/drm/i915/gt/intel_tlb.c
index af8cae979489..8eda0743da74 100644
--- a/drivers/gpu/drm/i915/gt/intel_tlb.c
+++ b/drivers/gpu/drm/i915/gt/intel_tlb.c
@@ -145,6 +145,18 @@ static void mmio_invalidate_full(struct intel_gt *gt)
 	intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL);
 }
 
+/**
+ * intel_gt_invalidate_tlb_full - do full TLB cache invalidation
+ * @gt: GT structure
+ * @seqno: sequence number
+ *
+ * Do a full TLB cache invalidation if the @seqno is bigger than the last
+ * full TLB cache invalidation.
+ *
+ * Note:
+ * The TLB cache invalidation logic depends on GEN-specific registers.
+ * It currently supports GEN8 to GEN12 and GuC-based TLB cache invalidation.
+ */
 void intel_gt_invalidate_tlb_full(struct intel_gt *gt, u32 seqno)
 {
 	intel_wakeref_t wakeref;
@@ -177,6 +189,12 @@ void intel_gt_init_tlb(struct intel_gt *gt)
 	seqcount_mutex_init(&gt->tlb.seqno, &gt->tlb.invalidate_lock);
 }
 
+/**
+ * intel_gt_fini_tlb - initialize TLB-specific vars
+ * @gt: GT structure
+ *
+ * Frees any resources needed by TLB cache invalidation logic.
+ */
 void intel_gt_fini_tlb(struct intel_gt *gt)
 {
 	mutex_destroy(&gt->tlb.invalidate_lock);
diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.h b/drivers/gpu/drm/i915/gt/intel_tlb.h
index 46ce25bf5afe..d186f5d5901f 100644
--- a/drivers/gpu/drm/i915/gt/intel_tlb.h
+++ b/drivers/gpu/drm/i915/gt/intel_tlb.h
@@ -11,16 +11,99 @@
 
 #include "intel_gt_types.h"
 
+/**
+ * DOC: TLB cache invalidation logic
+ *
+ * The way the current algorithm works is that drm_i915_gem_object can be
+ * created on any order. At unbind/evict time, the object is warranted that
+ * it won't be used anymore. So, they store a sequence number provided by
+ * intel_gt_next_invalidate_tlb_full().This can happen either at
+ * __vma_put_pages(), for VMA sync unbind, or at ppgtt_unbind_vma(), for
+ * VMA async VMA bind.
+ *
+ * At __i915_gem_object_unset_pages(), intel_gt_invalidate_tlb() is called,
+ * where it checks if the sequence number of the object was already invalidated
+ * or not. If not, it increments it::
+ *
+ *   void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
+ *   {
+ *   ...
+ * 	with_intel_gt_pm_if_awake(gt, wakeref) {
+ * 		mutex_lock(&gt->tlb.invalidate_lock);
+ * 		if (tlb_seqno_passed(gt, seqno))
+ * 				goto unlock;
+ *
+ * 		mmio_invalidate_full(gt);
+ *
+ * 		write_seqcount_invalidate(&gt->tlb.seqno); // increment seqno
+ *    ...
+ *
+ * So, let's say the current seqno is 2 and 3 new objects were created,
+ * on this order:
+ *
+ * 	obj1
+ * 	obj2
+ * 	obj3
+ *
+ * They can be unbind/evict on a different order. At unbind/evict time,
+ * the mm.tlb will be stamped with the sequence number, using the number
+ * from the last TLB flush, plus 1.
+ *
+ * Different threads may be used on unbind/evict and/or unset pages.
+ *
+ * As the logic at void intel_gt_invalidate_tlb() is protected by a mutex,
+ * for simplicity, let's consider just two threads::
+ *
+ *   sequence number	Thread 0		Thread 1
+ *
+ *   seqno=2
+ *			unbind/evict event
+ * 			obj3.mm.tlb = seqno | 1
+ *
+ *			unbind/evict event
+ * 			obj1.mm.tlb = seqno | 1
+ * 						__i915_gem_object_unset_pages()
+ * 						called for obj3 => TLB flush
+ * 						invalidating both obj1 and obj2.
+ * 						seqno += 2
+ *   seqno=4
+ *			unbind/evict event
+ * 			obj2.mm.tlb = seqno | 1
+ * 						__i915_gem_object_unset_pages()
+ * 						called for obj1, don't flush,
+ *						as past flush invalidated obj1
+ *
+ * 						__i915_gem_object_unset_pages()
+ *						called for obj2 => TLB flush
+ * 						seqno += 2
+ *   seqno=6
+ */
+
 void intel_gt_invalidate_tlb_full(struct intel_gt *gt, u32 seqno);
 
 void intel_gt_init_tlb(struct intel_gt *gt);
 void intel_gt_fini_tlb(struct intel_gt *gt);
 
+/**
+ * intel_gt_tlb_seqno - Returns the current TLB invlidation sequence number
+ *
+ * @gt: GT structure
+ *
+ * There's no need to lock while calling it, as seqprop_sequence is thread-safe
+ */
 static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt)
 {
 	return seqprop_sequence(&gt->tlb.seqno);
 }
 
+/**
+ * intel_gt_next_invalidate_tlb_full - Returns the next TLB full invalidation
+ *	sequence number
+ *
+ * @gt: GT structure
+ *
+ * There's no need to lock while calling it, as seqprop_sequence is thread-safe
+ */
 static inline u32 intel_gt_next_invalidate_tlb_full(const struct intel_gt *gt)
 {
 	return intel_gt_tlb_seqno(gt) | 1;

Re: [Intel-gfx] [PATCH v2 06/21] drm/i915/gt: Batch TLB invalidations

[Tvrtko Ursulin]

On 28/07/2022 07:32, Mauro Carvalho Chehab wrote:
> On Wed, 27 Jul 2022 13:56:50 +0100
> Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> 
>>> Because vma_invalidate_tlb() basically stores a TLB seqno, but the
>>> actual invalidation is deferred to when the pages are unset, at
>>> __i915_gem_object_unset_pages().
>>>
>>> So, what happens is:
>>>
>>> - on VMA sync mode, the need to invalidate TLB is marked at
>>>     __vma_put_pages(), before VMA unbind;
>>> - on async, this is deferred to happen at ppgtt_unbind_vma(), where
>>>     it marks the need to invalidate TLBs.
>>>
>>> On both cases, __i915_gem_object_unset_pages() is called later,
>>> when the driver is ready to unmap the page.
>>
>> Sorry still not clear to me why is the patch moving marking of the need
>> to invalidate (regardless if it a bit like today, or a seqno like in
>> this patch) from bind to unbind?
>>
>> What if the seqno was stored in i915_vma_bind, where the bit is set
>> today, and all the hunks which touch the unbind and evict would
>> disappear from the patch. What wouldn't work in that case, if anything?
> 
> Ah, now I see your point.
> 
> I can't see any sense on having a sequence number at VMA bind, as the
> unbind order can be different. The need of doing a full TLB invalidation
> or not depends on the unbind order.

Sorry yes that was stupid from me.. What I was really thinking was the 
approach I initially used for coalescing. Keeping the set_bit in bind 
and then once the code enters intel_gt_invalidate_tlbs, takes a "ticket" 
and waits on the mutex. Once it gets the mutex checks the ticket against 
the GT copy and if two invalidations have passed since it was waiting on 
the mutex it can immediately exit. That would seem like a minimal 
improvement to batch things up.

But I guess it would still emit needless invalidations if there is no 
contention, just a stream of serialized put pages. While the approach 
from this patch can skip all but truly required.

Okay, go for it and thanks for the explanations.

Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

P.S. The last remaining "ugliness" is the 2nd call to invalidation from 
evict. It would be nicer if there was a single common place to do it on 
vma unbind but okay, I do not plan to dig into it so fine.

> 
> The way the current algorithm works is that drm_i915_gem_object can be
> created on any order, and, at unbind/evict, they receive a seqno.
> 
> The seqno is incremented at intel_gt_invalidate_tlb():
> 
>      void intel_gt_invalidate_tlb(struct intel_gt *gt, u32 seqno)
>      {
> 	with_intel_gt_pm_if_awake(gt, wakeref) {
> 		mutex_lock(&gt->tlb.invalidate_lock);
> 		if (tlb_seqno_passed(gt, seqno))
> 				goto unlock;
> 
> 		mmio_invalidate_full(gt);
> 
> 		write_seqcount_invalidate(&gt->tlb.seqno);	// increment seqno
> 		
> 
> So, let's say 3 objects were created, on this order:
> 
> 	obj1
> 	obj2
> 	obj3
> 
> They would be unbind/evict on a different order. On that time,
> the mm.tlb will be stamped with a seqno, using the number from the
> last TLB flush, plus 1.
> 
> As different threads can be used to handle TLB flushes, let's imagine
> two threads (just for the sake of having an example). On such case,
> what we would have is:
> 
> seqno		Thread 0			Thread 1
> 
> seqno=2		unbind/evict event
> 		obj3.mm.tlb = seqno | 1
> seqno=2		unbind/evict event
> 		obj1.mm.tlb = seqno | 1
> 						__i915_gem_object_unset_pages()
> 						called for obj3, TLB flush happened,
> 						invalidating both obj1 and obj2.
> 						seqno += 2					
> seqno=4		unbind/evict event
> 		obj1.mm.tlb = seqno | 1
> 						__i915_gem_object_unset_pages()
> 						called for obj1, don't flush.
> ...
> 						__i915_gem_object_unset_pages() called for obj2, TLB flush happened
> 						seqno += 2
> seqno=6
> 
> So, basically the seqno is used to track when the object data stopped
> being updated, because of an unbind/evict event, being later used by
> intel_gt_invalidate_tlb() when called from __i915_gem_object_unset_pages(),
> in order to check if a previous invalidation call was enough to invalidate
> the object, or if a new call is needed.
> 
> Now, if seqno is stored at bind, data can still leak, as the assumption
> made by intel_gt_invalidate_tlb() that the data stopped being used at
> seqno is not true anymore.
> 
> Still, I agree that this logic is complex and should be better
> documented. So, if you're now OK with this patch, I'll add the above
> explanation inside a kernel-doc comment.
> 
> Regards,
> Mauro