gpu: nvgpu: improve nvs uapi

- Make the domain scheduler timeslice type nanoseconds to future proof
  the interface
- Return -ENOSYS from ioctls if the nvs code is not initialized
- Return the number of domains also when user supplied array is present
- Use domain id instead of name for TSG binding
- Improve documentation in the uapi headers
- Verify that reserved fields are zeroed
- Extend some internal logging
- Release the sched mutex on alloc error
- Add file mode checks in the nvs ioctls. The create and remove ioctls
  require writable file permissions, while the query does not; this
  allows filesystem based access control on domain management on the
  single dev node.

Jira NVGPU-6788

Change-Id: I668eb5972a0ed1073e84a4ae30e3069bf0b59e16
Signed-off-by: Konsta Hölttä <kholtta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2639017
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-cert <svc-mobile-cert@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: Gerrit_Virtual_Submit

include/uapi/linux/nvgpu-nvs.h

@@ -23,9 +23,9 @@
  */
 struct nvgpu_nvs_ioctl_domain {
 	/*
-	 * Human readable name for this domain.
+	 * Human readable null-terminated name for this domain.
 	 */
-	char		 name[32];
+	char name[32];
 
 	/*
 	 * Scheduling parameters: specify how long this domain should be scheduled
@@ -33,15 +33,15 @@ struct nvgpu_nvs_ioctl_domain {
 	 * preempting. A value of zero is treated as an infinite timeslice or an
 	 * infinite grace period, respectively.
 	 */
-	__u32		 timeslice_us;
-	__u32		 preempt_grace_us;
+	__u64 timeslice_ns;
+	__u64 preempt_grace_ns;
 
 	/*
 	 * Pick which subscheduler to use. These will be implemented by the kernel
 	 * as needed. There'll always be at least one, which is the host HW built in
 	 * round-robin scheduler.
 	 */
-	__u32		 subscheduler;
+	__u32 subscheduler;
 
 /*
  * GPU host hardware round-robin.
@@ -50,19 +50,21 @@ struct nvgpu_nvs_ioctl_domain {
 
 	/*
 	 * Populated by the IOCTL when created: unique identifier. User space
-	 * should never set this variable.
+	 * must set this to 0.
 	 */
-	__u64		 dom_id;
+	__u64 dom_id;
 
-	__u64		 reserved1;
-	__u64		 reserved2;
+	/* Must be 0. */
+	__u64 reserved1;
+	/* Must be 0. */
+	__u64 reserved2;
 };
 
 /**
  * NVGPU_NVS_IOCTL_CREATE_DOMAIN
  *
  * Create a domain - essentially a group of GPU contexts. Applications
- * cacan be bound into this domain on request for each TSG.
+ * can be bound into this domain on request for each TSG.
  *
  * The domain ID is returned in dom_id; this id is _not_ secure. The
  * nvsched device needs to have restricted permissions such that only a
@@ -81,16 +83,18 @@ struct nvgpu_nvs_ioctl_create_domain {
 	 */
 	struct nvgpu_nvs_ioctl_domain domain_params;
 
-	__u64		reserved1;
+	/* Must be 0. */
+	__u64 reserved1;
 };
 
 struct nvgpu_nvs_ioctl_remove_domain {
 	/*
 	 * In: a domain_id to remove.
 	 */
-	__u64		dom_id;
+	__u64 dom_id;
 
-	__u64		reserved1;
+	/* Must be 0. */
+	__u64 reserved1;
 };
 
 /**
@@ -99,26 +103,32 @@ struct nvgpu_nvs_ioctl_remove_domain {
  * Query the current list of domains in the scheduler. This is a two
  * part IOCTL.
  *
- * If domains is NULL, then this IOCTL will populate nr with the number
+ * If domains is 0, then this IOCTL will populate nr with the number
  * of present domains.
  *
- * If domains is not NULL, then this IOCTL will treat domains as an
- * array with nr elements and write up to nr domains into that array.
+ * If domains is nonzero, then this IOCTL will treat domains as a pointer to an
+ * array of nvgpu_nvs_ioctl_domain and will write up to nr domains into that
+ * array. The nr field will be updated with the number of present domains,
+ * which may be more than the number of entries written.
  */
 struct nvgpu_nvs_ioctl_query_domains {
 	/*
-	 * In/Out: If NULL, leave untouched. If not NULL, then write
-	 * up to nr domains into the domain elements pointed to by
-	 * domains.
+	 * In/Out: If 0, leave untouched. If nonzero, then write up to nr
+	 * elements of nvgpu_nvs_ioctl_domain into where domains points to.
 	 */
 	__u64 domains;
 
 	/*
-	 * In/Out: If domains is NULL, then populate with the number
-	 * of domains present. Otherwise nr specifies the capacity of
-	 * the domains array pointed to by domains.
+	 * - In: the capacity of the domains array if domais is not 0.
+	 * - Out: populate with the number of domains present.
 	 */
-	__u32		nr;
+	__u32 nr;
+
+	/* Must be 0. */
+	__u32 reserved0;
+
+	/* Must be 0. */
+	__u64 reserved1;
 };
 
 #define NVGPU_NVS_IOCTL_CREATE_DOMAIN			\

include/uapi/linux/nvgpu.h

@@ -41,9 +41,10 @@ struct nvgpu_tsg_bind_channel_ex_args {
 };
 
 struct nvgpu_tsg_bind_scheduling_domain_args {
-	/* in: name of the domain this tsg will be bound to */
-	__u8 domain_name[16];
-	__u8 reserved[16];
+	/* in: id of the domain this tsg will be bound to */
+	__u64 domain_id;
+	/* Must be set to 0 */
+	__u64 reserved[3];
 };
 
 /*