[PATCH v5 12/18] kvm: arm64: Configure VTCR_EL2.SL0 per VM

Suzuki K Poulose suzuki.poulose at arm.com
Mon Sep 17 03:41:34 PDT 2018


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 compute the value of SL0
for a VM based on the IPA size.

Cc: Marc Zyngier <marc.zyngier at arm.com>
Cc: Christoffer Dall <cdall at kernel.org>
Cc: Eric Auger <eric.auger at redhat.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
---
Changes since v3:
 - Update reference to latest ARM ARM.
 - Update per-vm VTCR value of SL0.
 - Add helpers to decode levels from SL0.
 - Didn't pick up Reviewed-by tag from Eric, as there
   are some new changes in this version
---
 arch/arm64/include/asm/kvm_arm.h | 51 +++++++++++++++++++++++++-------
 arch/arm64/kvm/reset.c           |  1 +
 2 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 3fb1d440be6e..5c1487dc5dca 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -121,7 +121,6 @@
 #define VTCR_EL2_IRGN0_WBWA	TCR_IRGN0_WBWA
 #define VTCR_EL2_SL0_SHIFT	6
 #define VTCR_EL2_SL0_MASK	(3 << VTCR_EL2_SL0_SHIFT)
-#define VTCR_EL2_SL0_LVL1	(1 << VTCR_EL2_SL0_SHIFT)
 #define VTCR_EL2_T0SZ_MASK	0x3f
 #define VTCR_EL2_VS_SHIFT	19
 #define VTCR_EL2_VS_8BIT	(0 << VTCR_EL2_VS_SHIFT)
@@ -148,29 +147,59 @@
 /*
  * Stage2 translation configuration:
  * 64kB pages (TG0 = 1)
- * 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			VTCR_EL2_TG0_64K
+#define VTCR_EL2_TGRAN_SL0_BASE		3UL
+
 #elif defined(CONFIG_ARM64_16K_PAGES)
 /*
  * Stage2 translation configuration:
  * 16kB pages (TG0 = 2)
- * 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			VTCR_EL2_TG0_16K
+#define VTCR_EL2_TGRAN_SL0_BASE		3UL
 #else	/* 4K */
 /*
  * Stage2 translation configuration:
  * 4kB pages (TG0 = 0)
- * 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			VTCR_EL2_TG0_4K
+#define VTCR_EL2_TGRAN_SL0_BASE		2UL
 #endif
 
-#define VTCR_EL2_FLAGS			(VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN_FLAGS)
+#define VTCR_EL2_FLAGS			(VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN)
+/*
+ * VTCR_EL2:SL0 indicates the entry level for Stage2 translation.
+ * Interestingly, it depends on the page size.
+ * See D.10.2.121, VTCR_EL2, in ARM DDI 0487C.a
+ *
+ *	-----------------------------------------
+ *	| 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_LVLS_TO_SL0(levels)	\
+	((VTCR_EL2_TGRAN_SL0_BASE - (4 - (levels))) << VTCR_EL2_SL0_SHIFT)
+#define VTCR_EL2_SL0_TO_LVLS(sl0)	\
+	((sl0) + 4 - VTCR_EL2_TGRAN_SL0_BASE)
+#define VTCR_EL2_LVLS(vtcr)		\
+	VTCR_EL2_SL0_TO_LVLS(((vtcr) & VTCR_EL2_SL0_MASK) >> VTCR_EL2_SL0_SHIFT)
 /*
  * ARM VMSAv8-64 defines an algorithm for finding the translation table
  * descriptors in section D4.2.8 in ARM DDI 0487C.a.
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index e0c49377b771..d9b7a00993b6 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -167,6 +167,7 @@ int kvm_arm_config_vm(struct kvm *kvm, unsigned long type)
 	vtcr |= (kvm_get_vmid_bits() == 16) ?
 		VTCR_EL2_VS_16BIT :
 		VTCR_EL2_VS_8BIT;
+	vtcr |= VTCR_EL2_LVLS_TO_SL0(kvm_stage2_levels(kvm));
 	kvm->arch.vtcr = vtcr;
 	return 0;
 }
-- 
2.19.0




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