cpu/x86/mtrr/earlymtrr: Validate MTRR arguments

The AMD64 Architecture Programmer's Manual, Volume 2: Systems
Programming says the following about variable MTRRs:

Variable Range Size and Alignment.
The size and alignment of variable memory-ranges (MTRRs) and I/O ranges
(IORRs) are restricted as follows:
* The boundary on which a variable range is aligned must be equal to the
range size. For example, a memory range of 16 Mbytes must be aligned on a
16-Mbyte boundary (i.e., naturally aligned).
* The range size must be a power of 2 (2^n , 52 > n > 11), with a minimum
allowable size of 4 Kbytes. For example, 4 Mbytes and 8 Mbytes are
allowable memory range sizes, but 6 Mbytes is not allowable.

Print out errors if these conditions are violated. I didn't assert since
`set_var_mtrr` can be used in boot block before the serial console is
enabled.

BUG=b:147042464
TEST=Boot trembyle and see MTRR errors:
MTRR Error: base 0xcc800000 must be aligned to size 0x1000000

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I8b8c734c7599bd89cf9f212ed43c2dd5b2c8ba7b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40762
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/cpu/x86/mtrr/earlymtrr.c b/src/cpu/x86/mtrr/earlymtrr.c
index e8608fd9cc..f96b05061f 100644
--- a/src/cpu/x86/mtrr/earlymtrr.c
+++ b/src/cpu/x86/mtrr/earlymtrr.c
@@ -4,6 +4,8 @@
 #include <cpu/cpu.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/x86/msr.h>
+#include <console/console.h>
+#include <commonlib/bsd/helpers.h>
 
 /* Get first available variable MTRR.
  * Returns var# if available, else returns -1.
@@ -34,6 +36,15 @@ void set_var_mtrr(
 	/* Bit 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);