[tip: x86/mtrr] x86/mtrr: Add get_effective_type() service function

[tip-bot2 for Juergen Gross]

The following commit has been merged into the x86/mtrr branch of tip:

Commit-ID:     1ca12099040fec8c6bbcd9fabf37f04ac0d08e48
Gitweb:        https://git.kernel.org/tip/1ca12099040fec8c6bbcd9fabf37f04ac0d08e48
Author:        Juergen Gross <jgross@xxxxxxxx>
AuthorDate:    Tue, 02 May 2023 14:09:25 +02:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Thu, 01 Jun 2023 15:04:33 +02:00

x86/mtrr: Add get_effective_type() service function

Add a service function for obtaining the effective cache mode of
overlapping MTRR registers.

Make use of that function in check_type_overlap().

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230502120931.20719-11-jgross@xxxxxxxx
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
---
 arch/x86/kernel/cpu/mtrr/generic.c | 39 ++++++++++++++---------------
 1 file changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 4d8ca62..b944271 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -80,31 +80,30 @@ static u64 get_mtrr_size(u64 mask)
 	return size;
 }
 
+static u8 get_effective_type(u8 type1, u8 type2)
+{
+	if (type1 == MTRR_TYPE_UNCACHABLE || type2 == MTRR_TYPE_UNCACHABLE)
+		return MTRR_TYPE_UNCACHABLE;
+
+	if ((type1 == MTRR_TYPE_WRBACK && type2 == MTRR_TYPE_WRTHROUGH) ||
+	    (type1 == MTRR_TYPE_WRTHROUGH && type2 == MTRR_TYPE_WRBACK))
+		return MTRR_TYPE_WRTHROUGH;
+
+	if (type1 != type2)
+		return MTRR_TYPE_UNCACHABLE;
+
+	return type1;
+}
+
 /*
  * Check and return the effective type for MTRR-MTRR type overlap.
- * Returns 1 if the effective type is UNCACHEABLE, else returns 0
+ * Returns true if the effective type is UNCACHEABLE, else returns false
  */
-static int check_type_overlap(u8 *prev, u8 *curr)
+static bool check_type_overlap(u8 *prev, u8 *curr)
 {
-	if (*prev == MTRR_TYPE_UNCACHABLE || *curr == MTRR_TYPE_UNCACHABLE) {
-		*prev = MTRR_TYPE_UNCACHABLE;
-		*curr = MTRR_TYPE_UNCACHABLE;
-		return 1;
-	}
-
-	if ((*prev == MTRR_TYPE_WRBACK && *curr == MTRR_TYPE_WRTHROUGH) ||
-	    (*prev == MTRR_TYPE_WRTHROUGH && *curr == MTRR_TYPE_WRBACK)) {
-		*prev = MTRR_TYPE_WRTHROUGH;
-		*curr = MTRR_TYPE_WRTHROUGH;
-	}
+	*prev = *curr = get_effective_type(*curr, *prev);
 
-	if (*prev != *curr) {
-		*prev = MTRR_TYPE_UNCACHABLE;
-		*curr = MTRR_TYPE_UNCACHABLE;
-		return 1;
-	}
-
-	return 0;
+	return *prev == MTRR_TYPE_UNCACHABLE;
 }
 
 /**