Subject: [PATCH v3 17/66] KVM: arm64: nv: Emulate PSTATE.M for a guest hypervisor

From: Marc Zyngier <[email-masked]>
Date: Thu, 10 Dec 2020 15:59:13 +0000

From: Christoffer Dall <[email-masked]>

We can no longer blindly copy the VCPU's PSTATE into SPSR_EL2 and return
to the guest and vice versa when taking an exception to the hypervisor,
because we emulate virtual EL2 in EL1 and therefore have to translate
the mode field from EL2 to EL1 and vice versa.

Signed-off-by: Christoffer Dall <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 43 +++++++++++++++++++++-
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
index e3901c73893e..92715fa01e88 100644
--- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
+++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
@@ -51,10 +51,32 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 	ctxt_sys_reg(ctxt, SPSR_EL1)	= read_sysreg_el1(SYS_SPSR);
 }
 
+static inline u64 from_hw_pstate(const struct kvm_cpu_context *ctxt)
+{
+	u64 reg = read_sysreg_el2(SYS_SPSR);
+
+	if (__is_hyp_ctxt(ctxt)) {
+		u64 mode = reg & (PSR_MODE_MASK | PSR_MODE32_BIT);
+
+		switch (mode) {
+		case PSR_MODE_EL1t:
+			mode = PSR_MODE_EL2t;
+			break;
+		case PSR_MODE_EL1h:
+			mode = PSR_MODE_EL2h;
+			break;
+		}
+
+		return (reg & ~(PSR_MODE_MASK | PSR_MODE32_BIT)) | mode;
+	}
+
+	return reg;
+}
+
 static inline void __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt->regs.pc			= read_sysreg_el2(SYS_ELR);
-	ctxt->regs.pstate		= read_sysreg_el2(SYS_SPSR);
+	ctxt->regs.pstate		= from_hw_pstate(ctxt);
 
 	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN))
 		ctxt_sys_reg(ctxt, DISR_EL1) = read_sysreg_s(SYS_VDISR_EL2);
@@ -131,9 +153,26 @@ static inline void __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt,
 	write_sysreg_el1(ctxt_sys_reg(ctxt, SPSR_EL1),	SYS_SPSR);
 }
 
+/* Read the VCPU state's PSTATE, but translate (v)EL2 to EL1. */
+static inline u64 to_hw_pstate(const struct kvm_cpu_context *ctxt)
+{
+	u64 mode = ctxt->regs.pstate & (PSR_MODE_MASK | PSR_MODE32_BIT);
+
+	switch (mode) {
+	case PSR_MODE_EL2t:
+		mode = PSR_MODE_EL1t;
+		break;
+	case PSR_MODE_EL2h:
+		mode = PSR_MODE_EL1h;
+		break;
+	}
+
+	return (ctxt->regs.pstate & ~(PSR_MODE_MASK | PSR_MODE32_BIT)) | mode;
+}
+
 static inline void __sysreg_restore_el2_return_state(struct kvm_cpu_context *ctxt)
 {
-	u64 pstate = ctxt->regs.pstate;
+	u64 pstate = to_hw_pstate(ctxt);
 	u64 mode = pstate & PSR_AA32_MODE_MASK;
 
 	/*
-- 
2.29.2

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