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/* * Copyright (c) 2011-2014 Wind River Systems, Inc. * Copyright (c) 2015 Intel Corporation * * SPDX-License-Identifier: Apache-2.0 */ /** * @file Utilities to read/write the Model Specific Registers (MSRs) */ #include <zephyr.h> /** * * @brief Write to a model specific register (MSR) * * This function is used to write to an MSR. * * The definitions of the so-called "Architectural MSRs" are contained * in kernel_structs.h and have the format: IA32_XXX_MSR * * INTERNAL * 1) The 'wrmsr' instruction was introduced in the Pentium processor; executing * this instruction on an earlier IA-32 processor will result in an invalid * opcode exception. * 2) The 'wrmsr' uses the ECX, EDX, and EAX registers which matches the set of * volatile registers! * * @return N/A */ void _MsrWrite(unsigned int msr, uint64_t msr_data) { __asm__ volatile ( "movl %[msr], %%ecx\n\t" "movl %[data_lo], %%eax\n\t" "movl %[data_hi], %%edx\n\t" "wrmsr" : : [msr] "m" (msr), [data_lo] "rm" ((uint32_t)(msr_data & 0xFFFFFFFF)), [data_hi] "rm" ((uint32_t)(msr_data >> 32)) : "eax", "ecx", "edx"); } /** * * @brief Read from a model specific register (MSR) * * This function is used to read from an MSR. * * The definitions of the so-called "Architectural MSRs" are contained * in kernel_structs.h and have the format: IA32_XXX_MSR * * INTERNAL * 1) The 'rdmsr' instruction was introduced in the Pentium processor; executing * this instruction on an earlier IA-32 processor will result in an invalid * opcode exception. * 2) The 'rdmsr' uses the ECX, EDX, and EAX registers which matches the set of * volatile registers! * * @return N/A */ uint64_t _MsrRead(unsigned int msr) { uint64_t ret; __asm__ volatile ( "movl %[msr], %%ecx\n\t" "rdmsr" : "=A" (ret) : [msr] "rm" (msr) : "ecx"); return ret; } |