[PATCH v3 11/20] kvm: arm64: Helper for computing VTCR_EL2.SL0

[Suzuki K Poulose]

VTCR_EL2 holds the following key stage2 translation table
parameters:
  SL0  - Entry level in the page table lookup.
  T0SZ - Denotes the size of the memory addressed by the table.

We have been using fixed values for the SL0 depending on the
page size as we have a fixed IPA size. But since we are about
to make it dynamic, we need to calculate the SL0 at runtime
per VM. This patch adds a helper to comput the value of SL0 for
a given IPA.

Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <cdall@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
Changes since v2:
 - Part 2 of split from VTCR & VTTBR dynamic configuration
---
 arch/arm64/include/asm/kvm_arm.h | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index c557f45..11a7db0 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -153,7 +153,8 @@
  * 2 level page tables (SL = 1)
  */
 #define VTCR_EL2_TGRAN_FLAGS		(VTCR_EL2_TG0_64K | VTCR_EL2_SL0_LVL1)
-#define VTTBR_X_TGRAN_MAGIC		38
+#define VTCR_EL2_TGRAN_SL0_BASE		3UL
+
 #elif defined(CONFIG_ARM64_16K_PAGES)
 /*
  * Stage2 translation configuration:
@@ -161,7 +162,7 @@
  * 2 level page tables (SL = 1)
  */
 #define VTCR_EL2_TGRAN_FLAGS		(VTCR_EL2_TG0_16K | VTCR_EL2_SL0_LVL1)
-#define VTTBR_X_TGRAN_MAGIC		42
+#define VTCR_EL2_TGRAN_SL0_BASE		3UL
 #else	/* 4K */
 /*
  * Stage2 translation configuration:
@@ -169,11 +170,39 @@
  * 3 level page tables (SL = 1)
  */
 #define VTCR_EL2_TGRAN_FLAGS		(VTCR_EL2_TG0_4K | VTCR_EL2_SL0_LVL1)
-#define VTTBR_X_TGRAN_MAGIC		37
+#define VTCR_EL2_TGRAN_SL0_BASE		2UL
 #endif
 
 #define VTCR_EL2_FLAGS			(VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN_FLAGS)
 /*
+ * VTCR_EL2:SL0 indicates the entry level for Stage2 translation.
+ * Interestingly, it depends on the page size.
+ * See D.10.2.110, VTCR_EL2, in ARM DDI 0487B.b
+ *
+ *	-----------------------------------------
+ *	| Entry level		|  4K  | 16K/64K |
+ *	------------------------------------------
+ *	| Level: 0		|  2   |   -     |
+ *	------------------------------------------
+ *	| Level: 1		|  1   |   2     |
+ *	------------------------------------------
+ *	| Level: 2		|  0   |   1     |
+ *	------------------------------------------
+ *	| Level: 3		|  -   |   0     |
+ *	------------------------------------------
+ *
+ * That table roughly translates to :
+ *
+ *	SL0(PAGE_SIZE, Entry_level) = SL0_BASE(PAGE_SIZE) - Entry_Level
+ *
+ * Where SL0_BASE(4K) = 2 and SL0_BASE(16K) = 3, SL0_BASE(64K) = 3, provided
+ * we take care of ruling out the unsupported cases and
+ * Entry_Level = 4 - Number_of_levels.
+ *
+ */
+#define VTCR_EL2_SL0(levels) \
+	((VTCR_EL2_TGRAN_SL0_BASE - (4 - (levels))) << VTCR_EL2_SL0_SHIFT)
+/*
  * ARM VMSAv8-64 defines an algorithm for finding the translation table
  * descriptors in section D4.2.8 in ARM DDI 0487B.b.
  *
-- 
2.7.4