Abstract: Embodiments relate to idle time accumulation in a multithreading computer system. According to one aspect, a computer-implemented method for idle time accumulation in a computer system is provided. The computer system includes a configuration having a plurality of cores and an operating system (OS)-image configurable between single thread (ST) mode and a multithreading (MT) mode in a logical partition. The MT mode supports multiple threads on shared resources per core simultaneously. The method includes executing a query instruction on an initiating core of the plurality of cores. The executing includes obtaining, by the OS-image, a maximum thread identification value indicating a current maximum thread identifier of the cores within the logical partition. The initiating core also obtains a multithreading idle time value for each of the cores indicating an aggregate amount of idle time of all threads enabled on each of the cores in the MT mode.

Abstract: Embodiments relate to idle time accumulation in a multithreading computer system. According to one aspect, a computer system includes a configuration having a plurality of cores and an operating system (OS)-image configurable between a single thread (ST) mode and a multithreading (MT) mode in a logical partition. The MT mode supports multiple threads on shared resources per core simultaneously. The computer system also includes a multithreading facility configured to perform a method that includes executing a query instruction on an initiating core of the plurality of cores. The executing includes obtaining, by the OS-image, a maximum thread identification value indicating a current maximum thread identifier of the cores within the logical partition. The initiating core also obtains a multithreading idle time value for each of the cores indicating an aggregate amount of idle time of all threads enabled on each of the cores in the MT mode.

Abstract: Management of storage used by pageable guests of a computing environment is facilitated. A query instruction is provided that details information regarding the storage location indicated in the query. It specifies whether the storage location, if protected, is protected by host-level protection or guest-level protection.

Abstract: A central processing unit measurement facility is virtualized in order to support concurrent use of the facility by multiple guests executing within a virtual environment. Each guest of the environment has independent control over disablement/enablement of the facility for that guest.

Abstract: Embodiments relate to dynamic enablement of multithreading. According to an aspect, a computer-implemented method for dynamic enablement of multithreading in a configuration is provided. The configuration includes a core configurable between a single thread (ST) mode and a multithreading (MT) mode, where the ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. The method includes executing in the primary thread in the ST mode, an MT mode setting instruction. A number of threads requested is obtained from a location specified by the MT mode setting instruction. Based on determining that the number of threads requested indicates multiple threads, the MT mode is enabled to execute the multiple threads including the primary thread and the one or more secondary threads.

Abstract: Embodiments relate to thread context restoration. One aspect is a multithreading computer system including a configuration with a core configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. A multithreading facility is configured to control utilization of the configuration to perform a method including disabling one or more secondary threads based on switching from MT mode to ST mode. A thread context of secondary threads is made unavailable to programs. Based on a last-set program-specified maximum thread-id indicating MT, the thread context is obtained by a) executing a set MT instruction to resume the MT mode, and b) based on being in the resumed MT mode, accessing the thread context.

Abstract: A central processing unit measurement facility is virtualized in order to support concurrent use of the facility by multiple guests executing within a virtual environment. Each guest of the environment has independent control over disablement/enablement of the facility for that guest.

Abstract: Embodiments relate to thread context restoration. One aspect is a multithreading computer system including a configuration with a core configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. A multithreading facility is configured to control utilization of the configuration to perform a method including disabling one or more secondary threads based on switching from MT mode to ST mode. A thread context of secondary threads is made unavailable to programs. Based on a last-set program-specified maximum thread-id indicating MT, the thread context is obtained by a) executing a set MT instruction to resume the MT mode, and b) based on being in the resumed MT mode, accessing the thread context.

Abstract: Embodiments relate to thread context restoration. One aspect is a multithreading computer system including a configuration with a core configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. A multithreading facility is configured to control utilization of the configuration to perform a method including disabling one or more secondary threads based on switching from MT mode to ST mode. A thread context of secondary threads is made unavailable to programs. Based on a last-set program-specified maximum thread-id indicating MT, the thread context is obtained by a) executing a set MT instruction to resume the MT mode, and b) based on being in the resumed MT mode, accessing the thread context.

Abstract: Embodiments relate to dynamic enablement of multithreading. According to an aspect, a computer system includes a configuration with a core configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread, and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. The computer system also includes a multithreading facility configured to control the configuration to perform a method. The method includes executing in the primary thread in the ST mode, an MT mode setting instruction. A number of threads requested is obtained from a location specified by the MT mode setting instruction. Based on determining that the number of threads requested indicates multiple threads, the MT mode is enabled to execute the multiple threads including the primary thread and the one or more secondary threads.

Abstract: Management of storage used by pageable guests of a computing environment is facilitated. A query instruction is provided that details information regarding the storage location indicated in the query. It specifies whether the storage location, if protected, is protected by host-level protection or guest-level protection.

Abstract: Embodiments relate to multithreading in a computer. An aspect is a computer including a configuration having a core which includes physical threads and is operable in single thread (ST) and multithreading (MT) modes. The computer also includes a host program configured to execute in the ST mode on the core to issue a start-virtual-execution (start-VE) instruction to dispatch a guest entity which includes a guest virtual machine (VM). The start-VE instruction is executed by the core and includes obtaining a state description, having a guest state, from a location specified by the start-VE instruction. The execution includes determining, based on the guest state, whether the guest entity includes a single guest thread or multiple guest threads, and starting the guest threads in the MT mode or ST mode based on the guest state and a determination of whether the guest entity includes a single guest thread or multiple guest threads.

Abstract: Embodiments relate to multithreading capability information retrieval. An aspect is a computer system includes a configuration with one or more cores configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of each core. The computer system also includes a multithreading facility configured to control utilization of the configuration to perform a method that includes executing, by the core, a retrieve multithreading capability information instruction. The execution includes obtaining thread identification information that identifies multithreading capability of the configuration, and storing the obtained thread identification information.

Abstract: According to one aspect, a computer system includes a configuration with a machine enabled to operate in a single thread (ST) mode and a multithreading (MT) mode. In addition, the machine includes physical threads. The machine is configured to perform a method that includes executing a guest entity on the core in MT mode. The guest entity includes all or a portion of a guest VM, and a plurality of logical threads executing on the physical threads. An exit event is detected at the machine. Based on detecting the exit event, the machine waits until all of the logical threads that are currently executing on the physical threads have reached a synchronization point. A state that includes exit reason information is saved for each of the logical threads and the execution of a host is initiated in the ST mode on one of the physical threads.

Abstract: Embodiments relate to idle time accumulation in a multithreading computer system. According to one aspect, a computer-implemented method for idle time accumulation in a computer system is provided. The computer system includes a configuration having a plurality of cores and an operating system (OS)-image configurable between single thread (ST) mode and a multithreading (MT) mode in a logical partition. The MT mode supports multiple threads on shared resources per core simultaneously. The method includes executing a query instruction on an initiating core of the plurality of cores. The executing includes obtaining, by the OS-image, a maximum thread identification value indicating a current maximum thread identifier of the cores within the logical partition. The initiating core also obtains a multithreading idle time value for each of the cores indicating an aggregate amount of idle time of all threads enabled on each of the cores in the MT mode.

Abstract: Embodiments relate to address expansion and contraction in a multithreading computer system. According to one aspect, a computer implemented method for address adjustment in a configuration is provided. The configuration includes a core configurable between an ST mode and an MT mode, where the ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. The primary thread is accessed in the ST mode using a core address value. Switching from the ST mode to the MT mode is performed. The primary thread or one of the one or more secondary threads is accessed in the MT mode using an expanded address value. The expanded address value includes the core address value concatenated with a thread address value.

Abstract: According to one aspect, a computer-implemented method for thread context preservation in a configuration including a core configurable between a single thread (ST) mode and a multithreading (MT) mode is provided. The ST mode addresses a primary thread, and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. Based on determining, by the core in the MT mode, that MT is to be disabled, switching from the MT mode to the ST mode is performed, where the primary thread of the MT mode is maintained as the primary thread of the ST mode. A thread context including program accessible register values and program counter values of the one or more secondary threads is made inaccessible to programs. Based on the switching, any one of clearing the program accessible register values or retaining the program accessible register values is performed.

Abstract: Embodiments relate to thread context restoration. One aspect is a multithreading computer system including a configuration with a core configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. A multithreading facility is configured to control utilization of the configuration to perform a method including disabling one or more secondary threads based on switching from MT mode to ST mode. A thread context of secondary threads is made unavailable to programs. Based on a last-set program-specified maximum thread-id indicating MT, the thread context is obtained by a) executing a set MT instruction to resume the MT mode, and b) based on being in the resumed MT mode, accessing the thread context.

Abstract: Embodiments relate to dynamic enablement of multithreading. According to an aspect, a computer-implemented method for dynamic enablement of multithreading in a configuration is provided. The configuration includes a core configurable between a single thread (ST) mode and a multithreading (MT) mode, where the ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of the core. The method includes executing in the primary thread in the ST mode, an MT mode setting instruction. A number of threads requested is obtained from a location specified by the MT mode setting instruction. Based on determining that the number of threads requested indicates multiple threads, the MT mode is enabled to execute the multiple threads including the primary thread and the one or more secondary threads.

Abstract: According to one aspect, a computer system includes a configuration with a machine enabled to operate in a single thread (ST) mode and a multithreading (MT) mode. In addition, the machine includes physical threads. The machine is configured to perform a method that includes issuing a start-virtual-execution (start-VE) instruction to dispatch a guest entity having multiple logical threads on the core. The guest entity includes all or a part of a guest virtual machine (VM), and issuing is performed by a host running on one of the physical threads on the core in the ST mode. The executing of the start-VE instruction by the machine includes mapping each of the logical threads to a corresponding one of the physical threads, initializing each of the mapped physical threads with a state of the corresponding logical thread, and starting execution of the guest entity on the core in MT mode.