geopm::MSRIO(3) – methods for reading and writing MSRs

Namespaces

The MSRIO class is a member of the namespace geopm, but the full name, geopm::MSRIO, has been abbreviated in this manual. Similarly, the std:: namespace specifier has been omitted from the interface definitions for the following standard types: std::vector, std::string, std::set, std::unique_ptr, std::shared_ptr to enable better rendering of this manual.

Synopsis

#include <geopm/MSRIO.hpp>

Link with -lgeopmd

virtual uint64_t MSRIO::read_msr(int cpu_idx,
                                 uint64_t offset) = 0;

virtual void MSRIO::write_msr(int cpu_idx,
                              uint64_t offset,
                              uint64_t raw_value,
                              uint64_t write_mask) = 0;

virtual int MSRIO::add_read(int cpu_idx, uint64_t offset) = 0;

virtual void MSRIO::read_batch(void) = 0;

virtual int MSRIO::add_write(int cpu_idx, uint64_t offset) = 0;

virtual void MSRIO::adjust(int batch_idx,
                           uint64_t value,
                           uint64_t write_mask) = 0;

virtual uint64_t MSRIO::sample(int batch_idx) const = 0;

virtual void MSRIO::write_batch(void) = 0;

static unique_ptr<MSRIO> MSRIO::make_unique(void);

static shared_ptr<MSRIO> MSRIO::make_shared(void);

Description

The MSRIO class handles reading and writing to Model-Specific Registers (MSRs). The implementation uses msr-safe, found at https://github.com/LLNL/msr-safe to allow access to a controlled set of MSRs from user space. Refer to geopm_pio_msr(7) for more details.

This class is an abstract base class.

Class Methods

read_msr(): Read from a single MSR at offset on the logical Linux CPU specified by cpu_idx. Returns the raw encoded MSR value.
write_msr(): Write to a single MSR at offset on the logical Linux CPU specified by cpu_idx. The value in raw_value will be masked with write_mask and the value will only be written for bits where the write_mask is 1. All other bits in the MSR will remain unmodified. If the raw_value tries to write any bits outside the mask, an error will be raised.
add_read(): Add an offset to the list of MSRs to be read by the next call to read_batch(), extend this set of MSRs with a single offset. The cpu_idx is the logical Linux CPU index to read from when read_batch() method is called. Returns the logical index that will be passed to sample().
read_batch(): Batch read a set of MSRs configured by a previous call to the batch_config() method. The memory used to store the result should have been returned by add_read(). The resulting raw encoded MSR values are accessible through sample().
add_write(): Add another offset to the list of MSRs to be written in batch. The cpu_idx is the logical Linux CPU index to write to when write_batch() method is called. Returns the logical index that will be passed to adjust().
adjust(): Adjust a value that was previously added with the add_write() method. The value in will be masked with write_mask and the value will only be written for bits where the write_mask is 1. All other bits in the MSR will remain unmodified. If the value tries to write any bits outside the mask, an error will be raised.
sample(): Read the full 64-bit value of the MSR that was previously added to the MSRIO batch with add_read(). read_batch() must be called prior to calling sample().
write_batch(): Batch write a set of MSRs configured by a previous call to the batch_config() method. The values in the raw_value vector will be written to the corresponding configured locations.
make_unique(): Returns a unique_ptr to a concrete object constructed using the underlying implementation
make_shared(): Returns a shared_ptr to a concrete object constructed using the underlying implementation

geopm::MSRIO(3) – methods for reading and writing MSRs

Namespaces

Synopsis

Description

Class Methods

See Also