write_resume_eip.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <acpi/acpi.h>
#include <arch/cpu.h>
#include <amdblocks/cpu.h>
#include <cpu/amd/msr.h>
#include <cpu/x86/msr.h>
#include <stdint.h>
 
asmlinkage void bootblock_resume_entry(void);
 
void write_resume_eip(void)
{
        msr_t s3_resume_entry = {
                .hi = (uint64_t)(uintptr_t)bootblock_resume_entry >> 32,
                .lo = (uintptr_t)bootblock_resume_entry & 0xffffffff,
        };
 
        /*
         * Writing to the EIP register can only be done once, otherwise a fault is triggered.
         * When this register is written, it will trigger the microcode to stash the CPU state
         * (crX , mtrrs, registers, etc) into the CC6 save area. On resume, the state will be
         * restored and execution will continue at the EIP.
         */
        if (!acpi_is_wakeup_s3())
                wrmsr(S3_RESUME_EIP_MSR, s3_resume_entry);
}