KVM: arm64: Refactor kvm_arm_setup_stage2()

In order to re-use some of the stage 2 setup code at EL2, factor parts
of kvm_arm_setup_stage2() out into separate functions.

No functional change intended.
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-23-qperret@google.com

arch/arm64/include/asm/kvm_pgtable.h

@@ -13,6 +13,16 @@
 
 #define KVM_PGTABLE_MAX_LEVELS		4U
 
+static inline u64 kvm_get_parange(u64 mmfr0)
+{
+	u64 parange = cpuid_feature_extract_unsigned_field(mmfr0,
+				ID_AA64MMFR0_PARANGE_SHIFT);
+	if (parange > ID_AA64MMFR0_PARANGE_MAX)
+		parange = ID_AA64MMFR0_PARANGE_MAX;
+
+	return parange;
+}
+
 typedef u64 kvm_pte_t;
 
 /**
@@ -159,6 +169,22 @@ void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt);
 int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
 			enum kvm_pgtable_prot prot);
 
+/**
+ * kvm_get_vtcr() - Helper to construct VTCR_EL2
+ * @mmfr0:	Sanitized value of SYS_ID_AA64MMFR0_EL1 register.
+ * @mmfr1:	Sanitized value of SYS_ID_AA64MMFR1_EL1 register.
+ * @phys_shfit:	Value to set in VTCR_EL2.T0SZ.
+ *
+ * The VTCR value is common across all the physical CPUs on the system.
+ * We use system wide sanitised values to fill in different fields,
+ * except for Hardware Management of Access Flags. HA Flag is set
+ * unconditionally on all CPUs, as it is safe to run with or without
+ * the feature and the bit is RES0 on CPUs that don't support it.
+ *
+ * Return: VTCR_EL2 value
+ */
+u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift);
+
 /**
  * kvm_pgtable_stage2_init() - Initialise a guest stage-2 page-table.
  * @pgt:	Uninitialised page-table structure to initialise.

arch/arm64/kvm/hyp/pgtable.c

@@ -9,6 +9,7 @@
 
 #include <linux/bitfield.h>
 #include <asm/kvm_pgtable.h>
+#include <asm/stage2_pgtable.h>
 
 #define KVM_PTE_VALID			BIT(0)
 
@@ -450,6 +451,37 @@ struct stage2_map_data {
 	struct kvm_pgtable_mm_ops	*mm_ops;
 };
 
+u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift)
+{
+	u64 vtcr = VTCR_EL2_FLAGS;
+	u8 lvls;
+
+	vtcr |= kvm_get_parange(mmfr0) << VTCR_EL2_PS_SHIFT;
+	vtcr |= VTCR_EL2_T0SZ(phys_shift);
+	/*
+	 * Use a minimum 2 level page table to prevent splitting
+	 * host PMD huge pages at stage2.
+	 */
+	lvls = stage2_pgtable_levels(phys_shift);
+	if (lvls < 2)
+		lvls = 2;
+	vtcr |= VTCR_EL2_LVLS_TO_SL0(lvls);
+
+	/*
+	 * Enable the Hardware Access Flag management, unconditionally
+	 * on all CPUs. The features is RES0 on CPUs without the support
+	 * and must be ignored by the CPUs.
+	 */
+	vtcr |= VTCR_EL2_HA;
+
+	/* Set the vmid bits */
+	vtcr |= (get_vmid_bits(mmfr1) == 16) ?
+		VTCR_EL2_VS_16BIT :
+		VTCR_EL2_VS_8BIT;
+
+	return vtcr;
+}
+
 static int stage2_map_set_prot_attr(enum kvm_pgtable_prot prot,
 				    struct stage2_map_data *data)
 {

arch/arm64/kvm/reset.c

@@ -329,19 +329,10 @@ int kvm_set_ipa_limit(void)
 	return 0;
 }
 
-/*
- * Configure the VTCR_EL2 for this VM. The VTCR value is common
- * across all the physical CPUs on the system. We use system wide
- * sanitised values to fill in different fields, except for Hardware
- * Management of Access Flags. HA Flag is set unconditionally on
- * all CPUs, as it is safe to run with or without the feature and
- * the bit is RES0 on CPUs that don't support it.
- */
 int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type)
 {
-	u64 vtcr = VTCR_EL2_FLAGS, mmfr0;
-	u32 parange, phys_shift;
-	u8 lvls;
+	u64 mmfr0, mmfr1;
+	u32 phys_shift;
 
 	if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
 		return -EINVAL;
@@ -361,33 +352,8 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type)
 	}
 
 	mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
-	parange = cpuid_feature_extract_unsigned_field(mmfr0,
-				ID_AA64MMFR0_PARANGE_SHIFT);
-	if (parange > ID_AA64MMFR0_PARANGE_MAX)
-		parange = ID_AA64MMFR0_PARANGE_MAX;
-	vtcr |= parange << VTCR_EL2_PS_SHIFT;
-
-	vtcr |= VTCR_EL2_T0SZ(phys_shift);
-	/*
-	 * Use a minimum 2 level page table to prevent splitting
-	 * host PMD huge pages at stage2.
-	 */
-	lvls = stage2_pgtable_levels(phys_shift);
-	if (lvls < 2)
-		lvls = 2;
-	vtcr |= VTCR_EL2_LVLS_TO_SL0(lvls);
-
-	/*
-	 * Enable the Hardware Access Flag management, unconditionally
-	 * on all CPUs. The features is RES0 on CPUs without the support
-	 * and must be ignored by the CPUs.
-	 */
-	vtcr |= VTCR_EL2_HA;
+	mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
+	kvm->arch.vtcr = kvm_get_vtcr(mmfr0, mmfr1, phys_shift);
 
-	/* Set the vmid bits */
-	vtcr |= (kvm_get_vmid_bits() == 16) ?
-		VTCR_EL2_VS_16BIT :
-		VTCR_EL2_VS_8BIT;
-	kvm->arch.vtcr = vtcr;
 	return 0;
 }