[PATCH] drm/amdgpu: Put drm_dev_enter/exit outside hot codepath

[xinhui pan]

We hit soft hang while doing memory pressure test on one numa system.
After a qucik look, this is because kfd invalid/valid userptr memory
frequently with process_info lock hold.

perf top says below,
75.81%  [kernel]       [k] __srcu_read_unlock
 6.19%  [amdgpu]       [k] amdgpu_gmc_set_pte_pde
 3.56%  [kernel]       [k] __srcu_read_lock
 2.20%  [amdgpu]       [k] amdgpu_vm_cpu_update
 2.20%  [kernel]       [k] __sg_page_iter_dma_next
 2.15%  [drm]          [k] drm_dev_enter
 1.70%  [drm]          [k] drm_prime_sg_to_dma_addr_array
 1.18%  [kernel]       [k] __sg_alloc_table_from_pages
 1.09%  [drm]          [k] drm_dev_exit

So move drm_dev_enter/exit outside gmc code, instead let caller do it.
They are gart_unbind, gart_map, vm_cpu_update(already hold in its
caller) and gmc_init_pdb0(no need)

Signed-off-by: xinhui pan <xinhui.pan at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c | 11 +++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c  |  7 -------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
index 76efd5f8950f..d7e4f4660acf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
@@ -34,6 +34,7 @@
 #include <asm/set_memory.h>
 #endif
 #include "amdgpu.h"
+#include <drm/drm_drv.h>
 
 /*
  * GART
@@ -230,12 +231,16 @@ int amdgpu_gart_unbind(struct amdgpu_device *adev, uint64_t offset,
 	u64 page_base;
 	/* Starting from VEGA10, system bit must be 0 to mean invalid. */
 	uint64_t flags = 0;
+	int idx;
 
 	if (!adev->gart.ready) {
 		WARN(1, "trying to unbind memory from uninitialized GART !\n");
 		return -EINVAL;
 	}
 
+	if (!drm_dev_enter(&adev->ddev, &idx))
+		return 0;
+
 	t = offset / AMDGPU_GPU_PAGE_SIZE;
 	p = t / AMDGPU_GPU_PAGES_IN_CPU_PAGE;
 	for (i = 0; i < pages; i++, p++) {
@@ -254,6 +259,7 @@ int amdgpu_gart_unbind(struct amdgpu_device *adev, uint64_t offset,
 	for (i = 0; i < adev->num_vmhubs; i++)
 		amdgpu_gmc_flush_gpu_tlb(adev, 0, i, 0);
 
+	drm_dev_exit(idx);
 	return 0;
 }
 
@@ -276,12 +282,16 @@ int amdgpu_gart_map(struct amdgpu_device *adev, uint64_t offset,
 {
 	uint64_t page_base;
 	unsigned i, j, t;
+	int idx;
 
 	if (!adev->gart.ready) {
 		WARN(1, "trying to bind memory to uninitialized GART !\n");
 		return -EINVAL;
 	}
 
+	if (!drm_dev_enter(&adev->ddev, &idx))
+		return 0;
+
 	t = offset / AMDGPU_GPU_PAGE_SIZE;
 
 	for (i = 0; i < pages; i++) {
@@ -291,6 +301,7 @@ int amdgpu_gart_map(struct amdgpu_device *adev, uint64_t offset,
 			page_base += AMDGPU_GPU_PAGE_SIZE;
 		}
 	}
+	drm_dev_exit(idx);
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
index 54f059501a33..e973488250e8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
@@ -31,7 +31,6 @@
 #include "amdgpu_ras.h"
 #include "amdgpu_xgmi.h"
 
-#include <drm/drm_drv.h>
 
 /**
  * amdgpu_gmc_pdb0_alloc - allocate vram for pdb0
@@ -153,10 +152,6 @@ int amdgpu_gmc_set_pte_pde(struct amdgpu_device *adev, void *cpu_pt_addr,
 {
 	void __iomem *ptr = (void *)cpu_pt_addr;
 	uint64_t value;
-	int idx;
-
-	if (!drm_dev_enter(&adev->ddev, &idx))
-		return 0;
 
 	/*
 	 * The following is for PTE only. GART does not have PDEs.
@@ -165,8 +160,6 @@ int amdgpu_gmc_set_pte_pde(struct amdgpu_device *adev, void *cpu_pt_addr,
 	value |= flags;
 	writeq(value, ptr + (gpu_page_idx * 8));
 
-	drm_dev_exit(idx);
-
 	return 0;
 }
 
-- 
2.25.1