src/cpu/x86/mtrr/earlymtrr.c

/* SPDX-License-Identifier: GPL-2.0-only */
/* This file is part of the coreboot project. */

#include <cpu/cpu.h>
#include <cpu/x86/cache.h>
#include <cpu/x86/mtrr.h>
#include <cpu/x86/msr.h>

/* Get first available variable MTRR.
 * Returns var# if available, else returns -1.
 */
int get_free_var_mtrr(void)
{
	msr_t maskm;
	int vcnt;
	int i;

	vcnt = get_var_mtrr_count();

	/* Identify the first var mtrr which is not valid. */
	for (i = 0; i < vcnt; i++) {
		maskm = rdmsr(MTRR_PHYS_MASK(i));
		if ((maskm.lo & MTRR_PHYS_MASK_VALID) == 0)
			return i;
	}

	/* No free var mtrr. */
	return -1;
}

void set_var_mtrr(
	unsigned int reg, unsigned int base, unsigned int size,
	unsigned int type)
{
	/* Bit Bit 32-35 of MTRRphysMask should be set to 1 */
	/* FIXME: It only support 4G less range */
	msr_t basem, maskm;
	basem.lo = base | type;
	basem.hi = 0;
	wrmsr(MTRR_PHYS_BASE(reg), basem);
	maskm.lo = ~(size - 1) | MTRR_PHYS_MASK_VALID;
	maskm.hi = (1 << (cpu_phys_address_size() - 32)) - 1;
	wrmsr(MTRR_PHYS_MASK(reg), maskm);
}