drm/amdkfd: Add available memory ioctl

Add a new KFD ioctl to return the largest possible memory size that
can be allocated as a buffer object using
kfd_ioctl_alloc_memory_of_gpu. It attempts to use exactly the same
accept/reject criteria as that function so that allocating a new
buffer object of the size returned by this new ioctl is guaranteed to
succeed, barring races with other allocating tasks.

This IOCTL will be used by libhsakmt:
https://www.mail-archive.com/amd-gfx@lists.freedesktop.org/msg75743.htmlSigned-off-by: Daniel Phillips <Daniel.Phillips@amd.com>
Signed-off-by: David Yat Sin <David.YatSin@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h

@@ -268,6 +268,7 @@ int amdgpu_amdkfd_gpuvm_acquire_process_vm(struct amdgpu_device *adev,
 void amdgpu_amdkfd_gpuvm_release_process_vm(struct amdgpu_device *adev,
 					void *drm_priv);
 uint64_t amdgpu_amdkfd_gpuvm_get_process_page_dir(void *drm_priv);
+size_t amdgpu_amdkfd_get_available_memory(struct amdgpu_device *adev);
 int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
 		struct amdgpu_device *adev, uint64_t va, uint64_t size,
 		void *drm_priv, struct kgd_mem **mem,

drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c

@@ -38,6 +38,12 @@
  */
 #define AMDGPU_USERPTR_RESTORE_DELAY_MS 1
 
+/*
+ * Align VRAM allocations to 2MB to avoid fragmentation caused by 4K allocations in the tail 2MB
+ * BO chunk
+ */
+#define VRAM_ALLOCATION_ALIGN (1 << 21)
+
 /* Impose limit on how much memory KFD can use */
 static struct {
 	uint64_t max_system_mem_limit;
@@ -108,7 +114,7 @@ void amdgpu_amdkfd_reserve_system_mem(uint64_t size)
  * compromise that should work in most cases without reserving too
  * much memory for page tables unnecessarily (factor 16K, >> 14).
  */
-#define ESTIMATE_PT_SIZE(mem_size) ((mem_size) >> 14)
+#define ESTIMATE_PT_SIZE(mem_size) max(((mem_size) >> 14), AMDGPU_VM_RESERVED_VRAM)
 
 static size_t amdgpu_amdkfd_acc_size(uint64_t size)
 {
@@ -148,7 +154,13 @@ static int amdgpu_amdkfd_reserve_mem_limit(struct amdgpu_device *adev,
 	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_VRAM) {
 		system_mem_needed = acc_size;
 		ttm_mem_needed = acc_size;
-		vram_needed = size;
+
+		/*
+		 * Conservatively round up the allocation requirement to 2 MB
+		 * to avoid fragmentation caused by 4K allocations in the tail
+		 * 2M BO chunk.
+		 */
+		vram_needed = ALIGN(size, VRAM_ALLOCATION_ALIGN);
 	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
 		system_mem_needed = acc_size + size;
 		ttm_mem_needed = acc_size;
@@ -173,7 +185,9 @@ static int amdgpu_amdkfd_reserve_mem_limit(struct amdgpu_device *adev,
 	    (kfd_mem_limit.ttm_mem_used + ttm_mem_needed >
 	     kfd_mem_limit.max_ttm_mem_limit) ||
 	    (adev->kfd.vram_used + vram_needed >
-	     adev->gmc.real_vram_size - reserved_for_pt)) {
+	     adev->gmc.real_vram_size -
+	     atomic64_read(&adev->vram_pin_size) -
+	     reserved_for_pt)) {
 		ret = -ENOMEM;
 		goto release;
 	}
@@ -205,7 +219,7 @@ static void unreserve_mem_limit(struct amdgpu_device *adev,
 	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_VRAM) {
 		kfd_mem_limit.system_mem_used -= acc_size;
 		kfd_mem_limit.ttm_mem_used -= acc_size;
-		adev->kfd.vram_used -= size;
+		adev->kfd.vram_used -= ALIGN(size, VRAM_ALLOCATION_ALIGN);
 	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
 		kfd_mem_limit.system_mem_used -= (acc_size + size);
 		kfd_mem_limit.ttm_mem_used -= acc_size;
@@ -1633,6 +1647,22 @@ int amdgpu_amdkfd_criu_resume(void *p)
 	return ret;
 }
 
+size_t amdgpu_amdkfd_get_available_memory(struct amdgpu_device *adev)
+{
+	uint64_t reserved_for_pt =
+		ESTIMATE_PT_SIZE(amdgpu_amdkfd_total_mem_size);
+	size_t available;
+
+	spin_lock(&kfd_mem_limit.mem_limit_lock);
+	available = adev->gmc.real_vram_size
+		- adev->kfd.vram_used
+		- atomic64_read(&adev->vram_pin_size)
+		- reserved_for_pt;
+	spin_unlock(&kfd_mem_limit.mem_limit_lock);
+
+	return ALIGN_DOWN(available, VRAM_ALLOCATION_ALIGN);
+}
+
 int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
 		struct amdgpu_device *adev, uint64_t va, uint64_t size,
 		void *drm_priv, struct kgd_mem **mem,

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -65,6 +65,25 @@ static int kfd_char_dev_major = -1;
 static struct class *kfd_class;
 struct device *kfd_device;
 
+static inline struct kfd_process_device *kfd_lock_pdd_by_id(struct kfd_process *p, __u32 gpu_id)
+{
+	struct kfd_process_device *pdd;
+
+	mutex_lock(&p->mutex);
+	pdd = kfd_process_device_data_by_id(p, gpu_id);
+
+	if (pdd)
+		return pdd;
+
+	mutex_unlock(&p->mutex);
+	return NULL;
+}
+
+static inline void kfd_unlock_pdd(struct kfd_process_device *pdd)
+{
+	mutex_unlock(&pdd->process->mutex);
+}
+
 int kfd_chardev_init(void)
 {
 	int err = 0;
@@ -958,6 +977,19 @@ bool kfd_dev_is_large_bar(struct kfd_dev *dev)
 	return false;
 }
 
+static int kfd_ioctl_get_available_memory(struct file *filep,
+					  struct kfd_process *p, void *data)
+{
+	struct kfd_ioctl_get_available_memory_args *args = data;
+	struct kfd_process_device *pdd = kfd_lock_pdd_by_id(p, args->gpu_id);
+
+	if (!pdd)
+		return -EINVAL;
+	args->available = amdgpu_amdkfd_get_available_memory(pdd->dev->adev);
+	kfd_unlock_pdd(pdd);
+	return 0;
+}
+
 static int kfd_ioctl_alloc_memory_of_gpu(struct file *filep,
 					struct kfd_process *p, void *data)
 {
@@ -2648,6 +2680,8 @@ static const struct amdkfd_ioctl_desc amdkfd_ioctls[] = {
 	AMDKFD_IOCTL_DEF(AMDKFD_IOC_CRIU_OP,
 			kfd_ioctl_criu, KFD_IOC_FLAG_CHECKPOINT_RESTORE),
 
+	AMDKFD_IOCTL_DEF(AMDKFD_IOC_AVAILABLE_MEMORY,
+			kfd_ioctl_get_available_memory, 0),
 };
 
 #define AMDKFD_CORE_IOCTL_COUNT	ARRAY_SIZE(amdkfd_ioctls)

include/uapi/linux/kfd_ioctl.h

@@ -34,9 +34,10 @@
  * - 1.6 - Query clear flags in SVM get_attr API
  * - 1.7 - Checkpoint Restore (CRIU) API
  * - 1.8 - CRIU - Support for SDMA transfers with GTT BOs
+ * - 1.9 - Add available memory ioctl
  */
 #define KFD_IOCTL_MAJOR_VERSION 1
-#define KFD_IOCTL_MINOR_VERSION 8
+#define KFD_IOCTL_MINOR_VERSION 9
 
 struct kfd_ioctl_get_version_args {
 	__u32 major_version;	/* from KFD */
@@ -100,6 +101,12 @@ struct kfd_ioctl_get_queue_wave_state_args {
 	__u32 pad;
 };
 
+struct kfd_ioctl_get_available_memory_args {
+	__u64 available;	/* from KFD */
+	__u32 gpu_id;		/* to KFD */
+	__u32 pad;
+};
+
 /* For kfd_ioctl_set_memory_policy_args.default_policy and alternate_policy */
 #define KFD_IOC_CACHE_POLICY_COHERENT 0
 #define KFD_IOC_CACHE_POLICY_NONCOHERENT 1
@@ -826,7 +833,10 @@ struct kfd_ioctl_set_xnack_mode_args {
 #define AMDKFD_IOC_CRIU_OP			\
 		AMDKFD_IOWR(0x22, struct kfd_ioctl_criu_args)
 
+#define AMDKFD_IOC_AVAILABLE_MEMORY		\
+		AMDKFD_IOWR(0x23, struct kfd_ioctl_get_available_memory_args)
+
 #define AMDKFD_COMMAND_START		0x01
-#define AMDKFD_COMMAND_END		0x23
+#define AMDKFD_COMMAND_END		0x24
 
 #endif