smm_helper.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <amdblocks/smm.h>
#include <console/console.h>
#include <cpu/x86/msr.h>
#include <cpu/amd/msr.h>
 
/*
 * For data stored in TSEG, ensure TValid is clear so R/W access can reach
 * the DRAM when not in SMM.
 */
void clear_tvalid(void)
{
        msr_t hwcr = rdmsr(HWCR_MSR);
        msr_t mask = rdmsr(SMM_MASK_MSR);
        int tvalid = !!(mask.lo & SMM_TSEG_VALID);
 
        if (hwcr.lo & SMM_LOCK) {
                if (!tvalid) /* not valid but locked means still accessible */
                        return;
 
                printk(BIOS_ERR, "can't clear TValid, already locked\n");
                return;
        }
 
        mask.lo &= ~SMM_TSEG_VALID;
        wrmsr(SMM_MASK_MSR, mask);
}