summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/cpu/mtrr/amd.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kernel/cpu/mtrr/amd.c')
-rw-r--r--arch/x86/kernel/cpu/mtrr/amd.c125
1 files changed, 125 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/amd.c b/arch/x86/kernel/cpu/mtrr/amd.c
new file mode 100644
index 000000000..a65a02720
--- /dev/null
+++ b/arch/x86/kernel/cpu/mtrr/amd.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <asm/mtrr.h>
+#include <asm/msr.h>
+
+#include "mtrr.h"
+
+static void
+amd_get_mtrr(unsigned int reg, unsigned long *base,
+ unsigned long *size, mtrr_type *type)
+{
+ unsigned long low, high;
+
+ rdmsr(MSR_K6_UWCCR, low, high);
+ /* Upper dword is region 1, lower is region 0 */
+ if (reg == 1)
+ low = high;
+ /* The base masks off on the right alignment */
+ *base = (low & 0xFFFE0000) >> PAGE_SHIFT;
+ *type = 0;
+ if (low & 1)
+ *type = MTRR_TYPE_UNCACHABLE;
+ if (low & 2)
+ *type = MTRR_TYPE_WRCOMB;
+ if (!(low & 3)) {
+ *size = 0;
+ return;
+ }
+ /*
+ * This needs a little explaining. The size is stored as an
+ * inverted mask of bits of 128K granularity 15 bits long offset
+ * 2 bits.
+ *
+ * So to get a size we do invert the mask and add 1 to the lowest
+ * mask bit (4 as its 2 bits in). This gives us a size we then shift
+ * to turn into 128K blocks.
+ *
+ * eg 111 1111 1111 1100 is 512K
+ *
+ * invert 000 0000 0000 0011
+ * +1 000 0000 0000 0100
+ * *128K ...
+ */
+ low = (~low) & 0x1FFFC;
+ *size = (low + 4) << (15 - PAGE_SHIFT);
+}
+
+/**
+ * amd_set_mtrr - Set variable MTRR register on the local CPU.
+ *
+ * @reg The register to set.
+ * @base The base address of the region.
+ * @size The size of the region. If this is 0 the region is disabled.
+ * @type The type of the region.
+ *
+ * Returns nothing.
+ */
+static void
+amd_set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type type)
+{
+ u32 regs[2];
+
+ /*
+ * Low is MTRR0, High MTRR 1
+ */
+ rdmsr(MSR_K6_UWCCR, regs[0], regs[1]);
+ /*
+ * Blank to disable
+ */
+ if (size == 0) {
+ regs[reg] = 0;
+ } else {
+ /*
+ * Set the register to the base, the type (off by one) and an
+ * inverted bitmask of the size The size is the only odd
+ * bit. We are fed say 512K We invert this and we get 111 1111
+ * 1111 1011 but if you subtract one and invert you get the
+ * desired 111 1111 1111 1100 mask
+ *
+ * But ~(x - 1) == ~x + 1 == -x. Two's complement rocks!
+ */
+ regs[reg] = (-size >> (15 - PAGE_SHIFT) & 0x0001FFFC)
+ | (base << PAGE_SHIFT) | (type + 1);
+ }
+
+ /*
+ * The writeback rule is quite specific. See the manual. Its
+ * disable local interrupts, write back the cache, set the mtrr
+ */
+ wbinvd();
+ wrmsr(MSR_K6_UWCCR, regs[0], regs[1]);
+}
+
+static int
+amd_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
+{
+ /*
+ * Apply the K6 block alignment and size rules
+ * In order
+ * o Uncached or gathering only
+ * o 128K or bigger block
+ * o Power of 2 block
+ * o base suitably aligned to the power
+ */
+ if (type > MTRR_TYPE_WRCOMB || size < (1 << (17 - PAGE_SHIFT))
+ || (size & ~(size - 1)) - size || (base & (size - 1)))
+ return -EINVAL;
+ return 0;
+}
+
+static const struct mtrr_ops amd_mtrr_ops = {
+ .vendor = X86_VENDOR_AMD,
+ .set = amd_set_mtrr,
+ .get = amd_get_mtrr,
+ .get_free_region = generic_get_free_region,
+ .validate_add_page = amd_validate_add_page,
+ .have_wrcomb = positive_have_wrcomb,
+};
+
+int __init amd_init_mtrr(void)
+{
+ set_mtrr_ops(&amd_mtrr_ops);
+ return 0;
+}