Change in coreboot[master]: cpu/x86/mtrr: Add check_var_mtrr_range_enabled() helper function

[Subrata Banik (Code Review)]

Subrata Banik has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/56151 )

Change subject: cpu/x86/mtrr: Add check_var_mtrr_range_enabled() helper function
......................................................................

cpu/x86/mtrr: Add check_var_mtrr_range_enabled() helper function

This patch creates a helper function to verify if a given address
range is belogs to variable MTRRs. check_var_mtrr_range_enabled()
function performs this check to know if the given address range
is cacheable.

Change-Id: I0df698c1501ad678ec0d58e133d7e437b658f4ca
Signed-off-by: Subrata Banik 
---
M src/cpu/x86/mtrr/earlymtrr.c
M src/include/cpu/x86/mtrr.h
2 files changed, 52 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/51/56151/1

diff --git a/src/cpu/x86/mtrr/earlymtrr.c b/src/cpu/x86/mtrr/earlymtrr.c
index aa301d0..2cd9428 100644
--- a/src/cpu/x86/mtrr/earlymtrr.c
+++ b/src/cpu/x86/mtrr/earlymtrr.c
@@ -132,3 +132,53 @@
 {
    return var_mtrr_set_with_cb(ctx, addr, size, type, set_mtrr);
 }
+
+static bool get_var_mtrr_range(int index, uintptr_t *base_address, size_t *length)
+{
+	bool ret = false;
+	uint32_t address_bits;
+	uint64_t address_mask;
+	const uint32_t msr_reg = MTRR_PHYS_BASE(index);
+	uint64_t mask;
+	union {
+		uint64_t u64;
+		msr_t s;
+	} msr_a;
+	union {
+		uint64_t u64;
+		msr_t s;
+	} msr_m;
+
+	address_bits = cpu_phys_address_size();
+	address_mask = (1ULL << address_bits) - 1;
+
+	msr_a.s = rdmsr(msr_reg);
+	msr_m.s = rdmsr(msr_reg + 1);
+	if (msr_m.u64 & MTRR_PHYS_MASK_VALID) {
+		*base_address = (msr_a.u64 & 0xfffffffffffff000ULL)
+				& address_mask;
+
+		mask = (msr_m.u64 & 0xfffffffffffff000ULL) & address_mask;
+		*length = (~mask & address_mask) + 1;
+		ret = true;
+	}
+	return ret;
+}
+
+bool check_var_mtrr_range_enabled(uintptr_t base, size_t size)
+{
+	uintptr_t base_address;
+	size_t length;
+	bool ret = false;
+	int variable_mtrrs_cnt = get_var_mtrr_count();
+	for (int i = 0; i < variable_mtrrs_cnt; i++) {
+		if (get_var_mtrr_range(i, &base_address, &length)) {
+			if (base_address == base && length == size) {
+				ret = true;
+				break;
+			}
+		}
+	}
+
+	return ret;
+}
diff --git a/src/include/cpu/x86/mtrr.h b/src/include/cpu/x86/mtrr.h
index b8d1517..097e0ea 100644
--- a/src/include/cpu/x86/mtrr.h
+++ b/src/include/cpu/x86/mtrr.h
@@ -96,6 +96,8 @@
 /* Set up fixed MTRRs but do not enable them. */
 void x86_setup_fixed_mtrrs_no_enable(void);
 void x86_mtrr_check(void);
+/* Function to check if a given address range is belongs to variable MTRRs */
+bool check_var_mtrr_range_enabled(uintptr_t base, size_t size);

/* Insert a temporary MTRR range for the duration of coreboot's runtime.
  * This function needs to be called after the first MTRR solution is derived. */