habanalabs/gaudi: monitor device memory usage

In GAUDI we don't have an MMU towards the HBM device memory. Therefore,
the user access that memory directly through physical address (via the
different engines) without the need to go through the driver to
allocate/free memory on the HBM.

For system monitoring purposes, the driver will keep track of the HBM
usage. This can be done as long as the user accurately reports the
allocations and releases of HBM memory, through the existing MEMORY
IOCTL uapi.
Signed-off-by: NOded Gabbay <ogabbay@kernel.org>

drivers/misc/habanalabs/common/memory.c

@@ -1236,18 +1236,35 @@ int hl_mem_ioctl(struct hl_fpriv *hpriv, void *data)
 
 	switch (args->in.op) {
 	case HL_MEM_OP_ALLOC:
-		if (!hdev->dram_supports_virtual_memory) {
-			dev_err(hdev->dev, "DRAM alloc is not supported\n");
-			rc = -EINVAL;
-			goto out;
-		}
-
 		if (args->in.alloc.mem_size == 0) {
 			dev_err(hdev->dev,
 				"alloc size must be larger than 0\n");
 			rc = -EINVAL;
 			goto out;
 		}
+
+		/* If DRAM does not support virtual memory the driver won't
+		 * handle the allocation/freeing of that memory. However, for
+		 * system administration/monitoring purposes, the driver will
+		 * keep track of the amount of DRAM memory that is allocated
+		 * and freed by the user. Because this code totally relies on
+		 * the user's input, the driver can't ensure the validity
+		 * of this accounting.
+		 */
+		if (!hdev->dram_supports_virtual_memory) {
+			atomic64_add(args->in.alloc.mem_size,
+					&ctx->dram_phys_mem);
+			atomic64_add(args->in.alloc.mem_size,
+					&hdev->dram_used_mem);
+
+			dev_dbg(hdev->dev, "DRAM alloc is not supported\n");
+			rc = 0;
+
+			memset(args, 0, sizeof(*args));
+			args->out.handle = 0;
+			goto out;
+		}
+
 		rc = alloc_device_memory(ctx, &args->in, &handle);
 
 		memset(args, 0, sizeof(*args));
@@ -1255,6 +1272,26 @@ int hl_mem_ioctl(struct hl_fpriv *hpriv, void *data)
 		break;
 
 	case HL_MEM_OP_FREE:
+		/* If DRAM does not support virtual memory the driver won't
+		 * handle the allocation/freeing of that memory. However, for
+		 * system administration/monitoring purposes, the driver will
+		 * keep track of the amount of DRAM memory that is allocated
+		 * and freed by the user. Because this code totally relies on
+		 * the user's input, the driver can't ensure the validity
+		 * of this accounting.
+		 */
+		if (!hdev->dram_supports_virtual_memory) {
+			atomic64_sub(args->in.alloc.mem_size,
+					&ctx->dram_phys_mem);
+			atomic64_sub(args->in.alloc.mem_size,
+					&hdev->dram_used_mem);
+
+			dev_dbg(hdev->dev, "DRAM alloc is not supported\n");
+			rc = 0;
+
+			goto out;
+		}
+
 		rc = free_device_memory(ctx, args->in.free.handle);
 		break;
 
@@ -1773,6 +1810,13 @@ void hl_vm_ctx_fini(struct hl_ctx *ctx)
 
 	mutex_destroy(&ctx->mem_hash_lock);
 	hl_mmu_ctx_fini(ctx);
+
+	/* In this case we need to clear the global accounting of DRAM usage
+	 * because the user notifies us on allocations. If the user is no more,
+	 * all DRAM is available
+	 */
+	if (!ctx->hdev->dram_supports_virtual_memory)
+		atomic64_set(&ctx->hdev->dram_used_mem, 0);
 }
 
 /*