[PATCH 80/89] KVM: arm64: Refactor enter_exception64()

[Will Deacon]

From: Quentin Perret <qperret at google.com>

In order to simplify the injection of exceptions in the host in pkvm
context, let's factor out of enter_exception64() the code calculating
the exception offset from VBAR_EL1 and the cpsr.

Signed-off-by: Quentin Perret <qperret at google.com>
---
 arch/arm64/include/asm/kvm_emulate.h |  5 ++
 arch/arm64/kvm/hyp/exception.c       | 89 ++++++++++++++++------------
 2 files changed, 57 insertions(+), 37 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 2a79c861b8e0..8b6c391bbee8 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -41,6 +41,11 @@ void kvm_inject_vabt(struct kvm_vcpu *vcpu);
 void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
 void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
 
+unsigned long get_except64_offset(unsigned long psr, unsigned long target_mode,
+				  enum exception_type type);
+unsigned long get_except64_cpsr(unsigned long old, bool has_mte,
+				unsigned long sctlr, unsigned long mode);
+
 void kvm_vcpu_wfi(struct kvm_vcpu *vcpu);
 
 static inline int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
index c5d009715402..14a80b0e2f91 100644
--- a/arch/arm64/kvm/hyp/exception.c
+++ b/arch/arm64/kvm/hyp/exception.c
@@ -60,31 +60,12 @@ static void __vcpu_write_spsr_und(struct kvm_vcpu *vcpu, u64 val)
 		vcpu->arch.ctxt.spsr_und = val;
 }
 
-/*
- * This performs the exception entry at a given EL (@target_mode), stashing PC
- * and PSTATE into ELR and SPSR respectively, and compute the new PC/PSTATE.
- * The EL passed to this function *must* be a non-secure, privileged mode with
- * bit 0 being set (PSTATE.SP == 1).
- *
- * When an exception is taken, most PSTATE fields are left unchanged in the
- * handler. However, some are explicitly overridden (e.g. M[4:0]). Luckily all
- * of the inherited bits have the same position in the AArch64/AArch32 SPSR_ELx
- * layouts, so we don't need to shuffle these for exceptions from AArch32 EL0.
- *
- * For the SPSR_ELx layout for AArch64, see ARM DDI 0487E.a page C5-429.
- * For the SPSR_ELx layout for AArch32, see ARM DDI 0487E.a page C5-426.
- *
- * Here we manipulate the fields in order of the AArch64 SPSR_ELx layout, from
- * MSB to LSB.
- */
-static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
-			      enum exception_type type)
+unsigned long get_except64_offset(unsigned long psr, unsigned long target_mode,
+				  enum exception_type type)
 {
-	unsigned long sctlr, vbar, old, new, mode;
+	u64 mode = psr & (PSR_MODE_MASK | PSR_MODE32_BIT);
 	u64 exc_offset;
 
-	mode = *vcpu_cpsr(vcpu) & (PSR_MODE_MASK | PSR_MODE32_BIT);
-
 	if      (mode == target_mode)
 		exc_offset = CURRENT_EL_SP_ELx_VECTOR;
 	else if ((mode | PSR_MODE_THREAD_BIT) == target_mode)
@@ -94,28 +75,32 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
 	else
 		exc_offset = LOWER_EL_AArch32_VECTOR;
 
-	switch (target_mode) {
-	case PSR_MODE_EL1h:
-		vbar = __vcpu_read_sys_reg(vcpu, VBAR_EL1);
-		sctlr = __vcpu_read_sys_reg(vcpu, SCTLR_EL1);
-		__vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL1);
-		break;
-	default:
-		/* Don't do that */
-		BUG();
-	}
-
-	*vcpu_pc(vcpu) = vbar + exc_offset + type;
+	return exc_offset + type;
+}
 
-	old = *vcpu_cpsr(vcpu);
-	new = 0;
+/*
+ * When an exception is taken, most PSTATE fields are left unchanged in the
+ * handler. However, some are explicitly overridden (e.g. M[4:0]). Luckily all
+ * of the inherited bits have the same position in the AArch64/AArch32 SPSR_ELx
+ * layouts, so we don't need to shuffle these for exceptions from AArch32 EL0.
+ *
+ * For the SPSR_ELx layout for AArch64, see ARM DDI 0487E.a page C5-429.
+ * For the SPSR_ELx layout for AArch32, see ARM DDI 0487E.a page C5-426.
+ *
+ * Here we manipulate the fields in order of the AArch64 SPSR_ELx layout, from
+ * MSB to LSB.
+ */
+unsigned long get_except64_cpsr(unsigned long old, bool has_mte,
+				unsigned long sctlr, unsigned long target_mode)
+{
+	u64 new = 0;
 
 	new |= (old & PSR_N_BIT);
 	new |= (old & PSR_Z_BIT);
 	new |= (old & PSR_C_BIT);
 	new |= (old & PSR_V_BIT);
 
-	if (kvm_has_mte(vcpu->kvm))
+	if (has_mte)
 		new |= PSR_TCO_BIT;
 
 	new |= (old & PSR_DIT_BIT);
@@ -151,6 +136,36 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
 
 	new |= target_mode;
 
+	return new;
+}
+
+/*
+ * This performs the exception entry at a given EL (@target_mode), stashing PC
+ * and PSTATE into ELR and SPSR respectively, and compute the new PC/PSTATE.
+ * The EL passed to this function *must* be a non-secure, privileged mode with
+ * bit 0 being set (PSTATE.SP == 1).
+ */
+static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
+			      enum exception_type type)
+{
+	u64 offset = get_except64_offset(*vcpu_cpsr(vcpu), target_mode, type);
+	unsigned long sctlr, vbar, old, new;
+
+	switch (target_mode) {
+	case PSR_MODE_EL1h:
+		vbar = __vcpu_read_sys_reg(vcpu, VBAR_EL1);
+		sctlr = __vcpu_read_sys_reg(vcpu, SCTLR_EL1);
+		__vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL1);
+		break;
+	default:
+		/* Don't do that */
+		BUG();
+	}
+
+	*vcpu_pc(vcpu) = vbar + offset;
+
+	old = *vcpu_cpsr(vcpu);
+	new = get_except64_cpsr(old, kvm_has_mte(vcpu->kvm), sctlr, target_mode);
 	*vcpu_cpsr(vcpu) = new;
 	__vcpu_write_spsr(vcpu, old);
 }
-- 
2.36.1.124.g0e6072fb45-goog