@@ -94,6 +94,8 @@ void setup_pcat_compatibility()
{
}
+#define MTRR_TYPE_WP 5
+#define MTRRcap_MSR 0xfe
#define MTRRphysBase_MSR(reg) (0x200 + 2 * (reg))
#define MTRRphysMask_MSR(reg) (0x200 + 2 * (reg) + 1)
@@ -101,11 +103,20 @@ int board_final_cleanup(void)
{
/* Un-cache the ROM so the kernel has one
* more MTRR available.
+ *
+ * Coreboot should have assigned this to the
+ * top available variable MTRR.
*/
- disable_cache();
- wrmsr(MTRRphysBase_MSR(7), 0);
- wrmsr(MTRRphysMask_MSR(7), 0);
- enable_cache();
+ u8 top_mtrr = (rdmsr(MTRRcap_MSR) & 0xff) - 1;
+ u8 top_type = rdmsr(MTRRphysBase_MSR(top_mtrr)) & 0xff;
+
+ /* Make sure this MTRR is the correct Write-Protected type */
+ if (top_type == MTRR_TYPE_WP) {
+ disable_cache();
+ wrmsr(MTRRphysBase_MSR(top_mtrr), 0);
+ wrmsr(MTRRphysMask_MSR(top_mtrr), 0);
+ enable_cache();
+ }
return 0;
}