mtrrlib.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <cpu/cpu.h>
#include <cpu/x86/mtrr.h>
#include <cpu/x86/msr.h>
#include <console/console.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 32-35 of MTRRphysMask should be set to 1 */
        /* FIXME: It only support 4G less range */
        msr_t basem, maskm;
 
        if (!IS_POWER_OF_2(size))
                printk(BIOS_ERR, "MTRR Error: size %#x is not a power of two\n", size);
        if (size < 4 * KiB)
                printk(BIOS_ERR, "MTRR Error: size %#x smaller than 4KiB\n", size);
        if (base % size != 0)
                printk(BIOS_ERR, "MTRR Error: base %#x must be aligned to size %#x\n", base,
                       size);
 
        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);
}
 
void clear_all_var_mtrr(void)
{
        msr_t mtrr = {0, 0};
        int vcnt;
        int i;
 
        vcnt = get_var_mtrr_count();
 
        for (i = 0; i < vcnt; i++) {
                wrmsr(MTRR_PHYS_MASK(i), mtrr);
                wrmsr(MTRR_PHYS_BASE(i), mtrr);
        }
}